caraterização e processos físico-químicos de recuperação ... · raras, lixiviação. iv v...

CaraterizaçãoeProcessosFísico-QuímicosdeRecuperaçãode

TerrasRarasemResíduos

JoanaRitaMeirelesFonseca

DissertaçãoparaaobtençãodograudeMestreem

EngenhariadeMateriais

Orientadores

ProfessoraDoutoraFernandaMariaRamosdaCruzMargarido

DoutorCarlosAlbertoGonçalvesNogueira

Júri

Presidente:ProfessorDoutorJoséPauloSequeiraFarinha

Orientador:DoutorCarlosAlbertoGonçalvesNogueira

Vogal:ProfessorDoutorManuelFranciscoCostaPereira

Outubrode2017

Declaration

Ideclarethatthisdocumentisanoriginalworkofmyownauthorshipandthatitfulfilsalltherequirements

oftheCodeofConductandGoodPracticesoftheUniversidadedeLisboa.

Declaração

Declaroqueopresentedocumentoéumtrabalhooriginaldaminhaautoriaequecumpretodososrequisitos

doCódigodeCondutaeBoasPráticasdaUniversidadedeLisboa.

“Ourimaginationistheonlylimittowhatwecanhopetohaveinthefuture.”

CharlesF.Kettering

ÀminhaMaria.

AomeuManuel.

i

AgradecimentosQueria começar por agradecer aosmeus orientadores, que sempre com umamaravilhosa disposição e

simpatia me transmitiram os conhecimentos necessários e permitiram crescer e desenvolver para além da

dissertaçãoedoTécnico.

Queriaagradeceraosmeuspais.Aocarinhodaminhamãe:osbeijoseabraçosdeconsoloou,somente

amizade,asrefeiçõeslevadasaoquarto,asvisitasàs5hdamanhãasuplicarparaeumeirdeitar,.Agradecero

facto de me ir buscar ao IST repetidamente, só porque já não haviam comboios para voltar para casa. À

intelectualidadeeperfecionismodomeupai.Semelenãoeratãopersistentenemtrabalhadora.Obrigadaaos

dois pelas oportunidades que sempre trabalharam para me proporcionar; pelo apoio incondicional e pelas

palavrasdesabedoria.

Aomeuirmão,queaindanoutropaís,sempremeapoiou,aindaquemecontinueatratarcomoumbebé.

Obrigadapelosconselhosde“comolidarcomoTécnico”,semelesnãotinhaalentoparaterminarocursoem5

anos.

Aos meus amigos de Materiais, que me acompanharam nesta viagem. Obrigada em especial à Rita

Faustino,ao André Estêvão, à Inês Cunha, aoMiguelMiguel, aoMiguel Costa, ao JoãoMiguel, ao Kiko, ao

HuguinhoeàPiquena,àMadalena,àsBias,àCatarina,aosmeusmeninosBernardo,Sempiterno,AndréeAdolfo

eaoMatepelasnoitesdeestudo,destresse,derisada,decopofonia.Pelaamizade.

Omesmoagradeçoaosmeusamigos,vulgo,daMargemSul.Quejápartilhamcomigomuitosmaisanose

muitasmaisaventuras.EmespecialaoLuísSantos,FredericoVelez,InêsAlexandre,InêsSerafim,ValériyaZaruba,

VicthorBörrénDias,JoanaFrancisco,DanielaMartinsCoelhoe,aindaquelonge,Di.

Finalmente,emais importante,aosmeusavósmaternos.Aindaqueumdelesnãoesteja jácomigo,não

possodeixardeestaragradecidaporter[tido]pessoastãofantásticaseamáveisnaminhavida.Pelosverõesna

“terrinha”, pelos lanches e refeições enormes feitas propositadamente ao meu gosto, pelo colinho, pelos

beijinhos,peloamorincondicionalquemederamequeserá,sempre,massempre,mútuo.

iii

ResumoAs lâmpadas fluorescentes contêmessencialmente seiselementosde terras-raras (ETRs): cério, európio,

gadolínio,lantânio,térbioeítrio.

NapresentedissertaçãoforamtestadasváriasmetodologiasderecuperaçãodosETRsdalamaproveniente

daoperaçãodepré-processamentodelâmpadasfluorescentes:1)doisprocessosdelixiviaçãosimples;2)dois

processos de lixiviação em vários passos com ácido clorídrico e/ou nítrico (testando diversas temperaturas,

concentraçãodeácido)e.3)doisprocessosdedigestãocomácidosulfúrico.

AssoluçõesdelixiviaçãonãoforamsubmetidasanenhumprocessoderecuperaçãodasETRs.

Os resíduos dos diferentes ensaios, após secagem foram submetidos a processos de caracterização por

pulverodifractometria de raios-X (DRXP),microscopia eletrónica de varrimento (MEV), granulometria laser e

espectrometriadeemissãoatómicaporplasmaacopladoindutivamente(ICP-AES).

Os seis ETRs foram identificados, e correspondem a aproximadamente 18% (peso seco) da amostra. O

processodedigestãosulfúricasimples(1,1mLg-1,3h,150°C)permitiuobterumrendimentodelixiviaçãosuperior

a99%paraolantânio,cérioetérbio,edeaproximadamente68%e73%paraoeurópioeoítrio,respetivamente.

Utilizandoumprocessoreativoadoispassos,oprimeirocomumalixiviaçãoácida(4MHCl,6h,90°C),seguido

por uma digestão sulfúrica (1,1mLg-1,3h, 150°C), obtiveram-se rendimentos de recuperação de ítrio mais

elevados(cercade86%),masvaloresmaisbaixosparaoeurópio(28%).

Os melhores resultados alcançados neste trabalho foram obtidos nas experiências com um passo de

digestão,sugerindoqueareatividadedosmetaiscomoácidosulfúricofoimaiordoquecomoácidoclorídrico

ounítrico.

Palavras-chave: Reciclagem, Lâmpadas fluorescentes, Fósforos luminescentes, elementos de terras-

raras,lixiviação.

v

AbstractThere are six main rare-earth elements (REEs) in fluorescent lighting: cerium, europium, gadolinium,

lanthanum,terbiumandyttrium.

ThepresentpublicationreviewsseveralleachingtechniquestoreclaimREEsfromfluorescentlampwaste.

Theinvestigationwasconductedinbench/laboratoryscaletoassesswhichleachingbasedprocesshasthemost

potential.Severalmulti-stepleachingprocesseswereinvestigatedsuchasleachingwithhydrochloricacidand/or

nitric or water (also named washing) as well as different parameters (temperature,leaching agent

concentration). A digestion with sulphuric acid was also studied. Separation of the leached REEs was not

performed.

The characterization of the waste was made using X-ray powder diffraction (XRD), scanning electron

microscopy (SEM), laser diffraction granulometry and Inductively Coupled Plasma – Atomic Emission

Spectrometer(ICP-AES).AllsixREEswereidentified,correspondingtoapprox.18%(drywt.)ofthesample.

Thepresentworkgaverisetothe leachingofallsix identifiedrareearthelements.Asulphuricdigestion

process(1,1mLg-1,3h,150°C)ledtoaleachingyieldofover99%forlanthanum,ceriumandterbiumandapprox.

68%and73%foreuropiumandyttrium,respectively.Atwo-stepreaction,startingwithanacidleaching(4M

HCl, 6h, 90°C), followed by a sulphuric acid digestion step (1,1mLg-1, 3h, 150°C), promoted higher yttrium

leachingyields(approx.86%),butlowervaluesforeuropium(approx.28%).Experimentswithadigestionstep

resulted in the best results attained in this work, consequently, it suggests that the metals reactivity with

sulphuricacidwashigherthanwithhydrochloricornitricacid.

Key-words:Recycling,FluorescentLamps,Phosphors,Rare-earthelements,Leaching.

vii

SummaryAGRADECIMENTOS...................................................................................................................................I

RESUMO.................................................................................................................................................III

ABSTRACT................................................................................................................................................V

SUMMARY.............................................................................................................................................VII

LISTOFFIGURES......................................................................................................................................IX

LISTOFTABLES.......................................................................................................................................XI

LISTOFACRONYMS...............................................................................................................................XIII

CHAPTER1. INTRODUCTION................................................................................................................1

1.1. GeneralRemarks.............................................................................................................................1

1.2. ProblemOverview...........................................................................................................................3

1.2.1. Rare-earthsascriticalelements..............................................................................................3

1.2.2. Geopoliticalproblem...............................................................................................................5

1.3. Scopeofthework............................................................................................................................7

CHAPTER2. RARE-EARTHELEMENTS...................................................................................................9

2.1. Rare-earthElements........................................................................................................................9

2.2. Depositsandmineralogy...............................................................................................................10

2.2.1. Maindeposits........................................................................................................................10

2.2.2. MineralogyofREEs................................................................................................................13

2.3. Balanceproblem............................................................................................................................14

2.4. Extractionandprocessing.............................................................................................................16

2.4.1. EnvironmentalImplications...................................................................................................18

2.4.2. HealthImpacts.......................................................................................................................19

2.5. REEsspecificationsanduses.........................................................................................................20

CHAPTER3. RECYCLING.....................................................................................................................23

3.1. RecyclingofEOLproductscontainingREEs....................................Erro!Marcadornão definido.

3.2. RecyclingofREEsinlampphosphors............................................................................................25

CHAPTER4. EXPERIMENTAL..............................................................................................................29

CHAPTER5. RESULTS.........................................................................................................................36

5.1. SamplingandPhysicalProcessing.................................................................................................36

viii

5.2. Characterization............................................................................................................................39

5.2.1. GrainsizemeasurementbyLaserDiffraction........................................................................39

5.2.2. X-RayPowderDiffraction......................................................................................................40

5.2.3. ScanningElectronMicroscopy...............................................................................................43

5.2.4. ElementalanalysisbyICP-AESofinitialsamples...................................................................46

5.3. Leachingofphosphormaterials....................................................................................................47

5.3.1. LeachingwithHClsolutions...................................................................................................47

5.3.2. Evaluationofseveralacidleachatesandmultistepleaching................................................48

CHAPTER6. CONCLUSIONANDFUTUREWORK..................................................................................53

BIBLIOGRAPHY.......................................................................................................................................55

ix

ListofFiguresFigure1.1–DivergenceofChinaExportquotaandROWdemand(adaptedfrom[6])..........................................3Figure1.2–Mediumtermcriticality(10years))ofsomeelementsaccordingtotheirsupplyriskandimportance

tocleanenergy(adaptedfrom[2,10])..........................................................................................................4Figure1.3–GlobalRare-earthOxide(REO)productiontrends[adaptedfrom[14]).............................................7Figure2.1–The17elements thatcomprise theREEsgroup.Theelementswithagreen frameare theLREE,

whereastheoneswiththeblueframe,theHREE.........................................................................................9Figure2.2–MainworldREEsdeposits(adaptedfrom[22])................................................................................11Figure2.3–Portugal’sregionswith[possible]REEoccurance.............................................................................12Figure2.4–Large/mediumoccurrenceofREEinValedeCavalosidentifiedbythebrowncircle(adaptedfrom

[24]...............................................................................................................................................................12Figure2.5–Resultingoutcomeofminingonetonofeuropiumoxide[5,15].....................................................15Figure2.6–General extractionandprocessingofREEsores. Theoperationsdesignatedby SXmean solvent

extraction:amulti-stepprocess[28]...........................................................................................................17Figure2.7–Productsofrefining1toneofREOs[22]...........................................................................................18

Figure2.8–Publishedarticlesreportingoneithertoxic(■)orstimulatory(o)effectsofindividualREE[31]..19Figure2.9–REEsingreentechnology(adaptedfrom[28])..................................................................................20Figure 3.1 – Alternative supplying: direct recycling of pre-consumer scrap or residues; urbanmining of EOL

consumergoodsandotherproducts;landfillminingoflandfilledpre-consumerandpost-consumerwaste

streams(adaptedfrom[2]).........................................................................................................................24Figure3.2–LifecycleofREEsinmajortechnologicalapplications(adaptedfrom[2])........................................24Figure3.3– Fluorescentlampdiagramwiththemainconstituents....................................................................26Figure4.1– Simplifiedsamplingdiagram.............................................................................................................33Figure5.1–IL3.15sample.....................................................................................................................................36Figure5.2–XRPDpatterns(Intensityvs2θ)forthedrysamplesanalysed.Fromtoptobottomorder:P.SP,P1,

P12,P19andPG...........................................................................................................................................41Figure5.3–XRPDpattern(Intensityvs2θ),with40 < 2θ < 60.Thephase(s)ofthecompoundscorrespondent

tothepeakis(are)identifiedbythesymbols:p-YOX;¿-Monazite;�-Hydroxylapatiteand¢-Alumina.

.....................................................................................................................................................................42Figure5.4–XRPDpattern(Intensityvs2θ),with60 < 2θ < 80.Thephase(s)ofthecompoundscorrespondent

tothepeakis(are)identifiedbythesymbols:p-YOX;¿-Monazite;�-Hydroxyapatiteand¢-Alumina.

.....................................................................................................................................................................42Figure5.5–SEMmicrographofP.12sample(200x).............................................................................................43Figure5.6–SEMmicrographofPGsample(200x)...............................................................................................43Figure5.7–SEMmicrographofP.SPsample(1500x),withtheeightstudiedparticles......................................44Figure5.8–SEMmicrographofPGsample(1500x).Particlesare:p–Calciumhalophosphate;u–YOX;À–

BAM;l–CAT;n–strontiumhalophosphate;Â–particlerichinFe.........................................................46

xi

ListofTablesTable1.1–Supplyanddemandfor2016,expressedinrare-earthoxides(REOs)[6]............................................2Table1.2–SummaryoftheBottleneckAnalysis:redimpliesahighrisk,yellowamediumriskandgreenalow

risk[8]............................................................................................................................................................4Table1.3–Considerablereserves,basicsupplyanddemandstatistics[11]..........................................................5Table2.1–Applicationanddemandgrowth(2011to2016).UnitsareintonsofREOs[6].................................16Table2.2–Rare-earthsusagebyapplicationinpercentage[31].Percentagesareroundedtothenearestdecimal.

Valuesmaynotaddtototalsshownowningtoindependentrounding.–noconsumption......................21Table2.3–DistributionofREOsconsumptionbymarketsectorin2008[31].ValuesareinmetrictonsofREOs.

.....................................................................................................................................................................21Table2.4–Useofrare-earthelementsinavarietyofdefence-relatedapplications[18]....................................22Table3.1–RecyclingpotentialsforREEsfromphosphors[2]..............................................................................25Table3.2–PublicationsregardingtheleachingofREEsfromlampphosphors...................................................28Table3.3–PublicationsdealingwithseparationsofREEsfromlampphosphorsbysolventextraction.............28Table4.1–TypesofSamples.The“X”codeimpliesthereareseveralsampleswithinagroup.Furthermore,the

valuetakenbytheXsisrelatedtotheLsamplesifX=number,ortothepulpfsX=SP..............................32Table4.2–Determinedleachingconditionsforexperiments1and2.................................................................34Table4.3–Determinedleachingconditionsforexperimentsthreetosix...........................................................35Table5.1–MoisturecontentofsamplesSP,L1,L12andL19...............................................................................37Table5.2–Masslosssintheproductionofthedrysamples.Massisexpressedisgrams(g).............................37Table5.3–Weightofthe32P.Xsamples,togetherwiththemasslossoftheprocess.Massisexpressedisgrams

(g).................................................................................................................................................................38Table5.4–MasslosssintheproductionoftheLGsamples.Massisexpressedisgrams(g)..............................38Table5.5–WeightoftheLGsamples,togetherwiththemasslossoftheprocess............................................38Table 5.6 – Particle SizeDistribution -D10,D50&D90 - SieveAnalysis. AM– arithmeticmean; SD – standard

deviation......................................................................................................................................................40Table5.7–NameofthecompoundsidentifiedbytheXRPDtechnique..............................................................41Table5.8–Atomicpercentageof theelementsconstitutingeachparticle (P.SPsample,particlenumbersare

thosefromFigure5.7)andmaininferredchemicalcompounds................................................................44Table5.9–Elementalcompositionof severalmetals inwaste fractions (wt.%).AM–arithmeticmean;SD–

standarddeviation.......................................................................................................................................46Table5.10–LeachingyieldsofREEsafterleachinginHClaccordingtoconditionsinTable4.2.Resultsin%.....47Table5.11–MassbalanceandvolumeofsolutionusedinexperimentsE1andE2.Samplesbythesameorderas.

Table5.10....................................................................................................................................................48Table5.12–MassbalanceandvolumeofsolutionusedineachexperimentE3-E6............................................49Table 5.13 –Overviewof the leaching behaviour of REEs (values of extractionpercentage for each step, not

accumulated)...............................................................................................................................................49Table5.14–Overallleachingyieldsattainedaftereachtreatmentprocess(6hofresidencetime)....................50

xii

Table5.15–ComparisonofREEsrecoverybetweenliteraturedataandpresentwork.......................................51

TableI.1–Selectedrare-earthmineralsbearingeitherLREEand/orHREE.........................................................59TableII.1–Summaryoftoxicologicalinformationwithrare-earths[30]............................................................63

xiii

ListofAcronymsBAM–BariumMagnesiumAluminate:Europiumdoped

CAT–CeriumMagnesiumAluminate:Terbium-doped

CBT–GadoliniumMagnesiumPentaborate:Cerium,erbiumdoped

CFL–CompactFluorescentLight

EOL–EndofLife

HREEs–HeavyRare-EarthElements

ICP-AES–InductivelyCoupledPlasma–AtomicEmissionSpectrometer

LAP–LanthanumPhosphate:Cerium,Terbiumdoped

LED–LightEmittingDiode

LREEs–LightRare-EarthElements

REEs–Rare-EarthElements

REMs–Rare-EarthMetals

REOs–Rare-EarthOxides

ROW–RestoftheWorld

SEM–ScanningElectronMicroscope

SX–SolventExtraction

XRD–X-RayDiffraction

YBCO–Yttrium-Barium-Copper-Oxide

YOX–YttriumOxide,EuropiumDoped

1

Chapter1. Introduction1.1. GeneralRemarks

Rare-earth elements (REEs) are specialty metals that comprise 15 lanthanides (from lanthanum up to

lutetium)togetherwithyttriumandscandium[1–3]sincetheseelementsarechemicallysimilar[4].

Since2010,REEshavebecomecriticalelementsfordevelopedanddevelopingcountries.Eventhoughmost

datafocusesonthelastdecadeandahalf,thefirstdiscoverywasmadein1788.

Thegivennameisrelatedtothefactthatupto1800noore,containingtheseelements,wasfoundexcept

oneinSweden.

Theseelementsareofparamount importance intermsof technology,especially in the latest technology

boom.REEsarecomprisedeverywhere inactual technology,namely inelectroniccomponents incomputers,

mobilesandTVscreens;ingreentechnologies,suchasmagnetsforwindgenerators,inductionelectricengines,

and war/defence industry. Although technology is presented as a life saver, problems arise with further

innovation.

Thefirstsuccessfulapplicationremotesto1880bythehandofCarlAuervonWelsbach.Itconsistedonagas

mantlewith1%ofCerium.Theproductionwasimmense,sinceby1930morethanfivebillionmantlesweresold

[4].

Afterwards,alightREEsalloynamed“mischmetal”madeuseoflargequantitiesofREEs’wastesfromthe

productionofWelsbach’smantelsandiron,ina7:3ratio.

Welsbach’stechnologicalandcommercialsuccesssparkedgreater interest inthebroaderapplicationsof

rare-earths,whichexpandedtherare-earthindustrydramaticallyanddrovethequestforrawmaterialsbeyond

Europe,totheAmericas,colonialIndia,andChina[4].

DuringWorldWarI,thepyrophoricpropertiesofrare-earthswereusedinfusesandexplosives.

InJuly1927,thegeologistDingDaohengdiscoveredtheresourcesatBayanObowhichisnowknownas‘the

rare-earthcapitaloftheworld.Thepresenceofrare-earthsatBayanObowasnotdemonstrateduntil10years

laterbythechemistHeZuolin[4].ThisdiscoveryshapedthenascentcommunistChineseindustrialgeography

asthenewlyestablishedPeople'sRepublicofChinarequiredthedevelopmentofnuclearweapons[4].

Inthefirsthalfofthedecade,researchersacrossEurasiaweredevelopingrare-earthsuperalloystousein

thesteelproductionprocesstotransformtheskeletalsystemofmodernityfromheavy,rust-proneandbrittle

to stronger, lighter, and more durable and to make the weapons of war more precise, long-range, and

devastating.Rare-earthswerethekeytodevelopingmaterials that remainstable in temperaturesashighas

1500degreesCelsius,thesortsoftemperaturesneededforrocketsandlong-rangemissiles[4].

The earliest application of pure REEs in the mid-1960s/early 1970s arises from the improvements in

separationtechniquesthusreducedthecostofeuropium[4,5].Europiumwasused inredphosphorsforTV

screens.TheimprovementintelevisionresultedinaburstofREEsapplications.Aroundthisera,europiumwas

themostcriticalREEduetoitslowabundanceandhighdemand[5].

2

These elements’ exceptional magnetic and conductive properties enabled in the 1970s and 80s the

production of samarium-cobalt magnets, thus turning samarium into the most critical REE. Nowadays, this

productrepresentslessthan2%ofpermanentmagnets’types.

Currentlythemarketisdictatedbytherequirementofneodymiumanddysprosium(Table1.1).Thefirstis

usedforNdFeBmagnets;onlyin2011,25000tonswereneededformagnetsproduction.Byminingthisnaturally

lowinabundanceconstituent,excessesofcerium,praseodymiumandsamariumwereproduced.

SinceheavyREEs(HREEs1)areproducedinmuchsmallerquantitiesthanlightREEs(LREEs2),thebalancing

problemisalotmoresignificantintheLREEmarket.Nowadays,theHREEsmarketis,asmentioned,drivenby

dysprosiumbecauseofitscapabilitytoincreasehigh-temperatureperformanceanddemagnetizationresistance

ofNdFeBmagnets.So,for25000tonsofNdusedtoproducethemagnets,1600tonsofDywhereneededto

fulfilthesameproduction.

ForsomeREEs(Eu,Y,ErandLa)theexistentsupplyequalsthedemand.Gd,Ho,Tm,YbandLuareproduced

inexcessand,therefore,stockpiled.AshortageinTbisverified.

Nowadays’demandsforNdandDyarenotthesameasbeforeastheseelementshavenotalwaysbeenthe

mostcritical.Thatcanbeidentifiedbythehistoricalevolution.

Table1.1–Supplyanddemandfor2016,expressedinrare-earthoxides(REOs)[6].

ElementDemand Supply Surplus(+)

tonnes % tonnes % Deficit(-)

La 36750 23.0 52000 26.7 15250

Ce 65000 40.6 81000 41.5 16000

Pr 7500 4.7 9500 4.9 2000

Nd 30000 18.8 31500 16.2 1500

Sm 1000 0.6 3750 1.9 2750

Eu 780 0.5 500 0.3 -280

Gd 2225 1.4 2750 1.4 525

Tb 450 0.3 350 0.2 -100

Dy 1650 1.0 1450 0.7 -200

Er 1000 0.6 800 0.4 -200

Y 13350 8.3 10000 5.1 -3350

Ho-Tm-Yb-Lu 250 0.2 1400 0.7 1150

Total 159955 100 195000 100 35045

1HeavyREEs:TerbiumuptoLutetium,aswellasYttriumandScandium;2LightREEs:LanthanumuptoGadolinium.

3

TheREEisafastmutablemarket.Newapplicationsand/orvanishingofcurrentwell-establishedapplications

canbringthemarketfurtheroutofbalance.Forthepasttwodecades,globaldemandforREEshasexperienced

arisingtendency.ThisisprojectedtocontinuetogrowasaresultofthedevelopingREEsupplychain.

WithChina’sdominanceofthesupplyofREEs,therestoftheworld(ROW)iscurrentlydependentonChinese

exportstomeetitsowngrowingneeds;however,recentbehaviourshavedemonstratedadesiretoretainmore

ofthematerialsforinternalconsumption.Chineseexportquotashavedeclinesince2012(Figure1.1).

Figure1.1–DivergenceofChinaExportquotaandROWdemand(adaptedfrom[6]).

1.2. ProblemOverview

1.2.1. Rare-earthsascriticalelements

Inrecentyears,therehavebeenexpressedconcerns,andmanyassessments,regardingthecriticalnature

ofthesupplyofcertainmineralrawmaterialstonationaleconomies.Majorriskfactorshavebeenidentified

includingtheconcentrationofproductionatthenationallevel,thepoliticalstabilityofproducingcountries,and

sudden demand peaks. The essential role high tech materials are playing in the developed countries for

innovativeapplicationsisnowwellrecognized.

In2008severalcommissionsoftheEU,USAandJapanamongstnumerousothers[3,7]releasedreportson

the roleof strategicminerals in their economy.An increasingnumberofelementswereassessedas “highly

critical” (Table 1.2) such as indium, cobalt, niobium, tantalum, rare-earth elements (REEs),lithiumand the

platinumgroupmetals[2,8].

4

Table1.2–SummaryoftheBottleneckAnalysis:redimpliesahighrisk,yellowamediumriskandgreenalowrisk[8].

Metal

MarketFactors PoliticalFactorsOverall

riskLikelihoodofrapid

demandgrowth

Limitationstoexpanding

productioncapacity

Concentrationof

supply

Political

risk

Dysprosium High High High High

High

Neodymium High Medium High High

Tellurium High High Low Medium

Gallium High Medium Medium Medium

Indium Medium High Medium Medium

Niobium High Low High Medium

MediumVanadium High Low Medium High

Tin Low Medium Medium High

Selenium Medium Medium Medium Low

Silver Low Medium Low High

Low

Molybdenum Medium Low Medium Medium

Hafnium Low Medium Medium Low

Nickel Medium Low Low Medium

Cadmium Low Low Low Medium

AccordingtoErdman[7],afteranalysingtenreportstudies(EUandUSAincluded),alldenotatedREEsas

critical.Thefivemostcriticalareneodymium(Nd),europium(Eu),terbium(Tb),dysprosium(Dy)andyttrium

(Y),ascanbeseeninFigure1.2,andareexpectedtobeshortinsupplyoverthenext10years[2,9,10].

Figure1.2–Mediumtermcriticality(10years))ofsomeelementsaccordingtotheirsupplyriskandimportancetoclean

energy(adaptedfrom[2,10]).

5

1.2.2. Geopoliticalproblem

Geological availability of REEs iswidespread.However, only a small proportion of these deposits are of

sufficient size that they can be explored economically [1]. In fact, there is a rare-earth elements’ Chinese

monopoly,nowthatChinaspecializesintheextractionofREOs3anddown-streamactivities,controlling97%of

the production and 89.7% of EU imports (Table 1.3). Worldwide reserves of rare-earth metals (excluding

scandium)areestimatedtobearound99milliontonnes(dataof2009)[11].

Giventhedemandfortheseelementsitisofimportancetoexaminewhethertheresourcesmeetmodern

societyneeds.Thereare largereservationsaboutestimatesofREEsavailability. It ispredictedthat,by2020,

therewillbeshortagesofNb,Dy,Eu,TbandY,asitisanticipatedthatoverthenext25yearsthedemandfor

neodymiumanddysprosiumwillriseby700%and2600%respectively[12].

Untilthe1980s,USwastheleaderinREEproductionandexploration.Withtimethatchanged,andcurrently

Chinaismanagingalmostallrare-earths’productionanddownstreamactivitiesdespiteonlypossessinglessthan

40%oftheworldreserves[2,3].Theproblemthatariseshereisageopolitical-economicavailability:highlevel

ofproductionconcentratedinfewcountries.Moreover,duetolargeandincreasingdomesticdemands,China

tighteneditsREEexportquotafrom50145tonsin2009toonly31130tons in2012,andareconstrainingit

increasingly.

Inanefforttomitigatethedamages,miningcompaniesarenotonlyreopeningoldmines,butalsoactively

seekingnewexploitableREEdeposits.Manycountrieswithoutoperationalprimarydepositsontheirterritory

willjusthavetorelyonrecyclingofREEsfromsecondarydeposits(pre-consumerscrap,industrialresiduesand

REE-containingEnd-of-Lifeproducts).

Table1.3–Considerablereserves,basicsupplyanddemandstatistics[11].

Reserves

(in103tons;2009)Production

(in103tons;2009)EUimports

(in103tons;2007)

USA 13000 13.2% - - -

Australia 5400 5.5% - - -

Brazil 48 <0.1% 0.65 0.5% -

China 36000 36.5% 120 97.0% 15.8 89.7%

India 3100 3.1% 2.7 2.2% 0.07 0.4%

Malaysia 30 <0.1% 0.38 0.3% - -

Kazakhstan - - - 0.1 0.6%

Russia - - - 1.6 9.2%

Vietnam - - - 0.01 0.1%

Others 41000 41.6% - - - -

Total 98578 123.7 17.6

3TheglobalproductionofREEistypicallyexpressedintonnesofrare-earthoxides(REOs).

6

By1970ChinaoverpassedtheUSdominationintheREEmarket(Figure1.3),floggingthemarket,inpartdue

tolowerlabourcostsandenvironmentalstandards.Thisresultedinapricedecrease,inhibitionofnewmining

projectsotherthaninChina.Beijingcontrolledtheentireproductionflowbyofferingindustriesandcompanies

reducedprices.Therewerescarcelyanyenvironmentalcontrol[13].

AccordingtotheCentreforEuropeanPolicyStudies(CEPS)PolicyBrief[13],by2010,Chinahadreduced

exportsby72%andincreasedexporttaxeson23rare-earthscategories(rare-earthoxides,unmixedandmixed

rare-earthchlorinates,oresofrare-earthmetals,rare-earthmaterialsintermixedorinter-alloyed,etc.)ranging

from25%onselectedrare-earths,primarilyheavyones,toupto15%onlightrare-earths.Forinstanceeuropium

rosewentfrom205.2€/kg(pricefrom2006)tonearly503.9€/kgwhileceriumfrom1.38€/kgto21.16€/kg[13].

Chinareducedexportratesfor3mainreasons.Firstandforemost,itaimstoincreaseself-manufactureofhigh-

techproducts.

ThisresultsinaneedandwantingfromWesternindustriestomovetheirfacilitiesandpatentsintoChinain

order to have more accessible rare-earths. China has a bonus of having access to new technologies and

innovationsgiventheshadowypropertyrightsenvironment/mentality.Therearealsouncertaintiesrelatedto

demand,supply,pricesandtheconceptofChinaitself,thatresultsinthemajorityofintervenientmarketsbeing

reluctant,uptonow,tore-locateproductiontoChina.[13].

Second,“Beijingaimstoincreaseitscontrolandconsolidateitsdomesticrare-earthsindustry”[13]by:

• Mergingminingcompanies(from120to10);

• Mergingprocessingfirms(from73to20);

• Establishingastockpilingsystem;

• Unifyingsupervisionofextraction;

• Settingupmonitoringsystemsforproduction,transportationandsales;

• Eliminatingproducerswithlessthan8000tonsofannualproduction[capacity].

Furthermore,BaotouSteelRare-earth,(supplies46%oftheglobalMarket)togetherwithJiangxiCopperare

interested in creating a unified pricing system for LREE. For analysts, these intended measures increased

significantly the prices. These measures also allow a strict control of production (by decreasing, for

instance,illegalminingandexports)andineconomicmonopoly[13].

Finally,Chinawantsthe“extremelyhighenvironmentalburden”.Likementionedbefore,theminingofREEs

anditsrefiningis,sometimes,associatedwithradioactiveslurriesandwiththetoxicacidused[13].

Regulationsarebeingdiscussedtoimproveproductiontechniques,whichwillimplytheclosingofnumerous

companies,affectingsuppliesandcontributing,furthermore,totherestrictiveconditions,i.e.reducedoutput

[13].

SinceexportsarecontrolledandcrampedbyChinesefees,environmentalregulationisauxiliaryinsteadof

havingaprimaryeffect.

7

Figure1.3–GlobalRare-earthOxide(REO)productiontrends[adaptedfrom[14]).

1.3. Scopeofthework

Duetotheincreasingsupplyrisk,thereisaninterestinrecyclingREEsfromend-of-lifeproducts.

It has been reported that recycling REEs would mitigate the main problem that arises from primary

exploitation, therefore having a stabilizing effect on prices, supply andquality of these elements andbased

materials[2,5,15].

Recyclingthemainwastestreamsimplies:

1. Recoveringhigherpercentageofelements,whencomparedtothepercentageobtainedwithprimary

ores;

2. Thereductionofthetotalamountoforesthatneedtobeexploitedinordertomeettheglobaldemand;

3. Thedecreaseofthebalancingproblemduetolessoverproduction;

4. ThepossibilityofmanycountriestohaveREEswithoutrelyingonnationaloperationalprimarydeposits

[iftheyexist]and/orabroadstocks.Despitethe[mandatory]needforrecyclingandthevastresearch

effort,upto2011lessthan1%wasrecycled[1].

Notwithstanding the environmental significance, it is industrially relevant to recycle the most valuable

applications:permanentmagnets,lampphosphors,Ni-MHbatteriesandcatalysts.Inthissense,theobjectiveof

thisworkistocontributetothedevelopmentofrecyclingprocessesofrare-earthscontainedinwastestreams,

namelyfocusingtheexperimentalworkinonespecificwaste,thefluorescentlamps.

ThisresearchworkhadbeencarriedoutinsideInstitutoSuperiorTécnico’sfacilities(IST,Lisboa,Portugal)

namelyMicroLab - ElectronMicroscopy Laboratory; Laboratory ofMineralogy and Petrology (LAMPIST) and

8

Laboratory ofWaste Processing andManagement, in collaboration with Laboratório Nacional de Energia e

Geologia(LNEG,Lisboa,Portugal).

SummarizingChapter1 ismeant to set the scenariowithinwhich thiswork stands, topresent themain

impedimentsregardingrare-earthandtofamiliarisethereaderwiththeresearchcarriedoutanditsgoals.

InChapter2,afteranintroductoryfirstsubchapterthatbrieflyexplainswhatREEare,ispresentedastateof

theartoftheprimaryexploitationofthesemetals.

Chapter3relatesthestateoftheartoftheprocessingofREEend-of-life(EOL)products.OverviewofREE

commercialapplicationsandsomeconsiderationsaboutrecyclingratesarepresented.

Chapter4iscommittedtothepresentationoftheworkplanrelatedtotheseveralleachingtechniquesto

reclaimREEsinrealfluorescentlampwaste,containingparticularly:cerium,europium,gadolinium,lanthanum,

terbiumandyttrium.

Chapters5referstothepresentationoftheresultstogetherwithasignificantdiscussionregardingthefinal

REErecovery.

Chapter6containsthestudy’sconclusionsandsomeinsightsforapossiblefuturecontinuationofthiswork.

9

Chapter2. Rare-earthElements2.1. Rare-earthElements

The rare-earthelements (REEs) area groupof seventeenelements: fifteen lanthanides (lanthanum (La),

cerium(Ce),praseodymium(Pr),neodymium(Nd),promethium(Pm),samarium(Sm),europium(Eu),gadolinium

(Gd),terbium(Tb),dysprosium(Dy),holmium(Ho),erbium(Er),thulium(Tm),ytterbium(Yb)andlutetium(Lu))

andtwotransitionmetals(yttrium(Y)andscandium(Sc)),sincetheseelementshavesimilarproperties[1–3].

REEsareinfactmetals.Metalsaredividedintofourcategories:ferrous,non-ferrous,preciousandspecialty.

REESareincludedinthespecialtymetals.[16]

AccordingtoREEHandbook,elementsfromlanthanum(atomicnumber57)togadolinium(atomicnumber

64), the ones with the lowest atomic weight, comprise the light rare-earth elements (LREEs) [17]. Terbium

(atomicnumber65)uptolutetium(atomicnumber71),aswellasyttrium(atomicnumber39)andscandium

(atomicnumber21)aretheheavyrare-earthelements(HREEs).Thisdivision,changesaccordingtosources.For

instance,in[1]and[18],LREEsgouptosamarium,whereasin[19]isuptoeuropium.

In this thesis, it is considered the division defended by the REE Handbook (Figure 2.1). The difference

between LREEs and HREEs, also named, cerium and yttrium group, respectively, is the electronic

configuration;thisdifferenceiscriticaltothepropertiesthateachREEdisplaysandhowitinteractswithother

elementsand/orcompounds.

Figure2.1–The17elementsthatcomprisetheREEsgroup.TheelementswithagreenframearetheLREE,whereasthe

oneswiththeblueframe,theHREE.

Despitetheirgroupnametheseelementsaremorefrequentthanmanyotherknownelements.REEsare

relativelyabundantintheearth’scrust,butminableconcentrationsarelesscommonthanformanyotherores.

Their natural occurrence is strongly dependent on geological features, and they are only found in sufficient

quantityandconcentrationinafewlocations,andinasuitableformandsetting,tomaketheirextractionand

exploitationeconomicallyviable.

10

LREEscoverupto99%oftheREEsresourses[1].Table2.1showstheaverageamountofsomeREEs,aswell

asotherelementsasaproportionoftheEarth’scontinentalcrust.TherarestREEisthulium(Tm)ifwedisregard

promethium(Pm)whichis,sinceitisaradioactiveelementwithashorthalf-life.Therecanbenoticedthatthese

elementshaveamuchhighervalueand,whencomparedtootherimportantelements,REEsabundancesarenot

soapart.

Table2.1– Abundanceofsomeelements[1].

Element Quantity(ppm)

Ce 43

La 20

Nd 20

Y 19

Tm 0,28

Cu 27

Li 17

Sn 1.7

Ge 1.3

U 1.3

2.2. Depositsandmineralogy

2.2.1. Maindeposits

Overtwohundredrare-earthmineralshavebeendescribed[1,19].However, inmanycasesthere isnot

enoughconcentrationofthesemineralstoeconomicallyjustifyminingandinothersthereisnoknownmethod

toextracttheREEfromtheoreeconomically.MineralstendtoberichineitherLREEsorHREEs,proportionsof

thedifferentREEswithinmineralsvarybetweendeposits. Ingeneral,REEsbearingmineralsare found in the

followingprimaryandsecondarygeologicalsettings[1,20,21]:

• Primary:

o Carbonatites(almostexclusivelyLREEs);

o Pegmatites(oralkalineigneousintrusivecomplexes);

o Hydrothermalveins(enrichedinHREEs);

• Secondary:

o Weathereddeposits/Laterites;

o Placers(mostlysandsofmarineorigin).

The main reserves are located in China (including Bayan Obo), Russia, Kyrgyzstan, Kazakhstan), USA

(including Mountain Pass) and Australia (including Mount Weld) (Figure 2.2). There are also resources in

India,Vietnam, Malaysia, Thailand, Indonesia, South Africa, Namibia, Mauritania, Burundi, Malawi,

Greenland,Canada,BrazilandPortugal[1].ThelargestknowndepositisinBayanObo,InnerMongolia,where

threedifferenttypesoforearedistinguished:Iron-REEsore,REEsoreindolomiteandREEsoreinsilicaterock

[1, 21]. Considerable REEs resources are related to pegmatites and carbonatites, such asMountain Pass, in

11

California,USA,andMountWeld,inWesternAustralia.Infact,beforeBayanObocameonstream,thelargest

singlesourceofREEswasMountainPass(whereminingceasedin2002).MountainPassisexpectedtomakea

significantcontributiontoglobalsupply,asarethedepositinweatheredcarbonatiteatMountWeld;thealkali

trachyte intrusionatDubbo,NewSouthWales,Australia(whereREEwillbeco-producedwithzirconiumand

othermetals);andafurthersmallermonazitedepositatSteenkampskraal,WesternCape,SouthAfrica[1].

Figure2.2–MainworldREEsdeposits(adaptedfrom[22]).

2.2.1.1. DepositsinPortugal

StudiesdemonstratedthatPortugal’sgeostructuralcharacteristicscontributetoagreatpotential for the

occurrence of rare-earths. Until recently, REEs were never mined in Portugal, apart from Alter Pedroso

zone,wherehyperalkalinerockshavebeeninvestigated[23].

Ageological survey, throughgeologicalmapping,alluvialandstreamsedimentsamplingandradiometric

surveys,exploredBeiraBaixaandAltoAlentejoregions.MiningaimsatthedetectionofREEsbearingminerals

suchasmonazite-nodularmonaziteinparticular-insedimentaryrockareas(moreorlessmetamorphosed)and

xenotime,apatiteandallanite[23].

DataaboutAltoAlentejosuggeststhat[nodular]monaziterichinLREEshasoriginatedprimarilyfromthe

disintegration of Ordovician quartzites on the southwest flank of the Portalegre Syncline. Normalmonazite

appearstobemainlyassociatedwithgranite(Fronteiragranite)[23].ReferredzonescanbeseeninFigure2.3.

12

Figure2.3–Portugal’sregionswith[possible]REEoccurance.

DatasuggeststhattheradioactivequartzitesinterstratifiedintheschistsareconstituentrichinREEs,and

nottheschistsitself.Thisverdict,goesagainstexistingdataonthelevelsofschistswithnodularmonazite(rich

inrare-earths,particularlyeuropium),inotherplacesinEuropeandAmerica[23].

Another study, taken by LNEG in 2010 [24], defined a feature of intra-xistent ordovician radioactive

quartzites(containingnodularmonazite),withanaveragethicknessof1mandanextensionof5.5kminValede

Cavalosregion(Figure2.4).

Figure2.4–Large/mediumoccurrenceofREEinValedeCavalosidentifiedbythebrowncircle(adaptedfrom[24].

13

Furtherstudyingwasmaderegardingthemainphasesthatcarrytherareearth(REEs)andtherearealso

evidencesofrareearthelementsinthePliocenesedimentsbetweenriversVougaandMondego[25].

2.2.2. MineralogyofREEs

Mineral groups include silicates (e.g.eudialyte, allanite); carbonates (e.g.bastnäsite, synchisite,

parasite,fluocerite, ancylite), oxides (e.g.euxenite, aeschnite, fergusenite, loparite) and phosphates (e.g.

xenotime,florencite,monazite)(AnnexI–TableI.1)[19,20].

NowadaystherearefourREEsbearingmineralspeciesbeingexploitedcommercially:

• Bastnäsite,aLREEfluorocarbonate(ChinaandUSA);

• Monazite,aLREE/HREEphosphate(Australia);

• Xenotime,aHREEyttriumphosphate(Malyasia);

• LateriticorecontainingHREErichionadsorptionclaysinChina.

SinceseveralREEshavesimilarproperties(physicalandchemical)theytendtooccurtogetherthereforethey

arerecoveredfromthesamemineralhost(AnnexI–TableI.1).Succeedingthatfact,thechemicalprocessesto

separateandconcentratetheseelementsinvolveadditionalcost.

Bastnäsite[20]

Thisfluorocarbonatemineral,(Ce,La,Nd,Pr)CO3F,isthemostimportantsourceforREEs.Ittendstocontain

copiousLREEs(specificallycerium,lanthanum,yttrium,andneodymium)andverylowproportionsofHREEs.

The realmineral environment inwhich bastnäsite is recovered is farmore complex than the simplified

chemicalformulaofthesinglemineralinfact,severalREEfluorocarbonatemineralsareknown.Variouscommon

substitutions in thechemistryofbastnäsite, i.e. ranges in themetalportionof thesolid solution,generatea

seriesofrelatedmineralsthatmaybefoundtogetherinbastnäsiticores.Threevariationsinnomenclatureare

usedtodescribeafewcommonranges:bastnäsite-(Ce),bastnäsite-(Y),andbastnäsite-(La).

It isalsopossible,bythesubstitutionofthefluorineorcarbonateanions,toobtainrelatedmineralslike:

parisite,andvarioushydroxylbastnäsites,interalia.

Bastnäsite ores have been found in a variety of igneous environments: carbonatites,

granites,pegmatites,hydrothermalandbauxitedeposits.

Monazite[20]

Monazite is the second most common mineral used as a rare-earth ore. It has also variations in the

nomenclatures according to the primary elemental composition of the ores: monazite-Ce, monazite-

La,monazite-Nd,andmonazite-Pr.Theoverallchemicalformulais(Ce,La)PO4.

ItcontainspredominantlyLREEsandcomprises,always,amixofvariousrare-earths.However,itishabitually

associatedwithslightlyhigherratiosofHREEsthantheonesfoundinbastnäsite.

Radioactive spin-offs are a dare in somemonazitemining locations, due to the capability of thorium, a

radioactiveelement,tosubstitutefortherare-earths inthemonazitestructure.Theseby-products, including

uranium,maybecomemineableco-productsinextremecases.

14

Xenotime[20]

Isthethirdmostimportantrare-earthelementoreandit,typically,containsthehighestratiosofHREEsout

ofthethreemainmineralores.

ThegeneralizedchemicalformulaisYPO4.TheyttriumiseasilysubstitutedbyseveralHREEsasdysprosium,

ytterbium,erbium,andgadolinium.Nevertheless,itcanbereplacedbyfewerquantitiesofterbium,holmium,

thulium,andlutetium,aswellasuraniumandthorium.Notethaturaniumandthoriumarenot insignificant

quantities, like inxenotimeores,howeverarepresenteitherasmineableby-productor impurity,depending

entirelyupontheminecontext,quantityandlocation.

Xenotimeandmonazitecanberelatedsincetheyaresimilarphosphates.Thefirstiscomposedmainlyby

yttrium,who is then freely substitutedby variousHREEs, asmentioned.Whereasmonazite is developedby

cerium,whichissubstitutedbythevariousLREEs.

These two ores can be found together, representing a continuous mineral formation established upon

modifications in temperature and pressure. At lower temperatures and pressures occurs the formation of

monazite,while athigher temperatures andpressures, xenotime is formed. The variationof the conditions

resultsinchangesinthecrystalstructureofthephosphateasoneortheotherREEsgroup(LREEsandHREEs)

getsexcludedfromthelattice.Thephosphateportionofxenotimeandmonaziteconstitutessignificantmineable

co-productsintheseores.

2.3. Balanceproblem

AnotherproblemarisesfromtheprimaryexplorationofREEs,thesocalled“balanceproblem”.Notonly

theseelementsoccurtogether,but,andmoreimportant,theyoccurindifferentratiosintheirselectedminerals

andores,asitwasobservedin2.2.2.

BastnäsiteandmonazitearerichinLREEs,whilstxenotimeandionadsorptionclaysarerichinHREEs.

Asmentioned before, the balance is tipped towards LREEs since they comprise 99% of resources, then

depositswithahighproportionofHREEareveryrare.Thisfactisrelatedtothegeneraltrendthattheseelements

verify.WithincreasingatomicnumberZ,therarertheybecome,i.e.abundancedecreasesalongthelanthanide

series.Soitcanbestated[andre-confirmed]thatHREEsaremuchlessplentifulthanLREEs.

AssaidbytheSwissAcademyofEngineering[26],globaldemandinREEsannuallyis132500tonnes(data

of 2008). Even though rare-earths are found in the crust, few are the depositsworth exploring.Worldwide

reservesareestimatedataround99milliontonnes(dataof2009),andthemajorityofdepositsarelocatedin

China(38%),CommonwealthofIndependentStates(19%)andUS(13%).

Apartfromtheseelementsnaturaltippedoccurrence(geographicallyandquantitiesintheores),thereis

also the fact that the majority of HREEs play a crucial role in emerging green energy and high tech

applications,and,therefore,aremorevaluablethanLREEs(Table2.2).Thisresults inaveryhighdemandfor

specificREEs, that areaminor constituent,while thedemandof themajor constituent ismuch lower. Even

thoughthedemandandsupplymustbeequal[atanygiventime],duetothedifferentabundancetherewillbe

lacking or overloading of certain elements. This will increase even more the overall price of REEs due to

stockpiling.

15

Forexample, theminingofeuropium (that ismuch less) frombastnäsite4willproduce largeamountsof

lanthanum,cerium,praseodymium(muchmorecommonsincetheyareinhigherrateintheminerals),thathave

tobesoldthen(Figure2.5)[15].

Figure2.5–Resultingoutcomeofminingonetonofeuropiumoxide[5,15].

Thedeficientbalancebetweenthedemandbythe[economic]marketsandthenaturaloccurrenceofthese

elementscreatesthe,socalled,“balanceproblem”or“balancingproblem”.

Thisproblemimplicatesthattheindustrymustfirstly,findnewapplicationsfortheREEsinexcessandsearch

forsubstitutionalelements for thoseminorREEs.Tobalance theLREEsmarket,high-volumeapplications for

samarium,praseodymiumandceriumareessential.AsecondoptionistodiversifythetypesofexploredREEs

ores,consideringlesscommononeslikeloparite(Ce,Na,Ca)(Ti,Nb)2O6[5,15].

Athirdapproachisrecycling.SpeciallycomparedtotheprimaryminingofREEs,notonlysolvesthebalance

problembutalsoreducesthetotalamountofREEsoresthatneedtobeextractedandallowstheattainmentof

REEswithhigherandsimplerconcentration[5].Forinstance,byrecyclingphosphorslampswewouldbeableto

recoverY,Ce,La,Eu,Tb(Table2.3).

DependenceonChina,whichhasreinedinitsexportsofrare-earths,asitwillbediscussedahead,canonly

be reduced if deposits outside China are mined, or if recycling is intensified. Therefore, to fulfil this

purpose,processes, inorder toextractREEs fromoresand recycleREEs’endof life (EOL)products,mustbe

developed.

Currentmarketreliesonthemaincomponents indemand:magnetsandmetalalloys,bothofwhichare

responsible forconsumingapproximately21000 tonnesofREOequivalents in2011.Magnetsconstitute the

largestportionofdemandin2016(Table2.2),reaching36000tonnes[6].

4Bastnäsiteisricherineuropiumthanmonazite:0.1%versus<0.05%.

16

Table2.2–Applicationanddemandgrowth(2011to2016).UnitsareintonsofREOs[6].

2011 2016

Application China ROW TOTAL % China ROW TOTAL %

Catalyst 11000 9000 20000 19 1500 9500 25000 16

Glass 5500 2500 8000 8 7000 3000 10000 6

Polishing 10500 3500 14000 13 13000 5000 18000 11

Metalalloys 15000 6000 21000 20 23000 7000 30000 19

Magnets 16500 4500 21000 20 28000 8000 36000 23

Phosphors 5000 3000 8000 8 8000 3500 12000 8

Ceramics 3000 4000 7000 7 4000 6000 10000 6

Other 3500 2500 6000 6 5000 14000 19000 12

Σ 70000 35000 105000 100 104000 56000 160000 100

TheindustrycontinuestoincreaseanddiversifythesupplychainandnewsourcesofdemandforREEswill

arise.Inbrief,theavailabilityoftheseelementsisdeterminedbytheproductionvolumesofREEsores,natural

abundanceandtherequestsituation.

Theexpectedsourcesthatwillhaveanimpactonthemarketdynamicinclude[6]:

• Magnetorestrictors[foractuators,acoustics,micropositioner,sonar,valves,micropumps,andsatellite

telescopes];

• Magnetic Refrigeration: Applications in home/auto air conditioning, household appliances.

Typically,gadoliniumbasedalloyswithdysprosium,erbium,andothernon-REEsmaterials.

• Magnetooptics:Useoflaserstowrite,read,anderaseinformationonterbium-basedthinfilms(upto

50timeshigherstoragedensityversusmagneticharddisks).Yttriumisalsoused;

• Superconductors (YBCO [yttrium-barium-copper-oxide]): High-temperature conductors with

applicationsincircuitry,powergenerators,electricstorageunits,andelectricmotors.

2.4. Extractionandprocessing

NumerousminingandprocessingtechniquesareusedforthetransformationofREEs’bearingminerals,due

tothediversityofthesedeposits.Themajorityincludesthermaltreatmentoftheoreconcentrateinthepresence

ofacidicorcausticreagents.Thechoiceofthedecompositionmethodisdoneaccordingtotheoreconcentrate.

Ithastobenotedthat,sincerare-earthsarecommonlyexploitedasothermetals’by-products,thesewill

determinetheeconomicsoftheoperationsandtechniquesused.Forinstance,REEsextractedinChinaareaby-

productofironoreextraction.InRussiafromtitaniumextraction,whereasinCanadarare-earthswererecovered

fromuraniumexploitation.

An opinion article presented in the Le Monde exposed ignored problems to promote technological

innovation[27].

17

Regardingworkingconditions, labourhasbeenincreasinglyexportedtonationswithcheap[almostfree]

manpowerandminimaltonoregulationsasisthecaseofChinesemanufacturingsites.Moreover,althoughit

resultsincheaptechnology,productsarenotmadethatcheap,astheexampleofApple.

Secondly,therearesubstantialenvironmentalcostsconcerningtheprimaryexploitation.Onehastoextract

them,thenpurificationisneededandfinallythepureREEsareimplementedintotechproducts.

Theextractionprocessisratherunclean.Althoughthereareminingprocessesthatallowcleanmetalsthey

comeatagreatercost.Sincethecostisdemandedbythemanufactures,theminingindustryisforcedtoremain

dirtyandpollutant.Theextractionresultsinsubstantialpollutionintheminingsites:soillossanddegradation,

leachingintogroundwater,lakesriversand,asaresult,bioaccumulation.

Overall,theattainmentprocessofREEfromthemainoresischaracterizedbyfourmainsteps(Figure2.6):

• Extraction;

• Flotation (physical beneficiation process): there is the separation of the valuableminerals from the

wasteor“gangue”allowingtheattainmentofmineralconcentrate;

• Hydrometallurgy:solubilisationofthevaluableminerals;

• Separation:AmixtureofREOsresultsfromtheprocessabove,henceseparationisneededinorderto

obtainindividualrare-earthcompounds(oxides,carbonates,etc).

Figure2.6–GeneralextractionandprocessingofREEsores.TheoperationsdesignatedbySXmeansolventextraction:

amulti-stepprocess[28].

18

2.4.1. EnvironmentalImplications

Firstofall, likeotherextractiveoperations,theprimaryexploitationofREEsusessubstantialamountsof

energythatare,mostly,suppliedbycoalpowerstations[22].Thisaidstheincreaseofthemainenvironmental

concerns:climatechangeandincreasingcarbonemissions.

However,theuseofrare-earthsintechnologicalproductsallowsabetterenvironmentalfriendlyoutcome.

Theuseofnickel-lanthanumrechargeablebatteries,insteadofnickel-cadmiumones,reducescadmiumorlead

toxicityissues[sinceitdoesnotincludetheminthecomposition].Furthermore,theuseofREEsinfluorescent

lamps,aswellas inmagneticrefrigerationsignificantly increasesenergyefficiencyand,thereby,reduces𝐶𝑂,

emissions[22].

Anothercomplicationthatarisesfromprimaryobtainmentistheradioactivityofsomeores.Asmentioned

in 2.2.2, xenotime andmonazite are related to radioactive, and sometimesmineable, co-products. For this

reason,manyminesandplantswereclosed.

Ion adsorption clay deposits have lower radioactive element content. However, additional problems

develop:in-situminingtechniquesaremoreenvironmentallyfriendly,buttherearesomeconcernsaboutthe

injectionofstrongreagentsintotheground[29].

Concerningbastnäsite, itsdepositscarrysignificantdangersduetothechemicalsused intheprocessing.

Reports show that processing of bastnäsite has caused: water pollution, farmland destruction and human

poisoning.

OveralltherefiningofonetoneofREOscanproducetonsofwasteproductsandpollutants,ascanbeseen

inFigure2.7.

Figure2.7–Productsofrefining1toneofREOs[22].

19

2.4.2. HealthImpacts

Regarding the impacts in human health, some studies were done. One is aware that after human

interference, REEs can accumulate in mining areas due to its low mobility leading to soil and water

contamination,bioaccumulationand[chronic]toxicity[30].Bycomparingtoxicological literatureon inorganic

xenobiotics5,regardingREEslittleinformationisavailableabouthealtheffects,theexistingonefocusesonfew

elements [28, 29]. For instance, database is mostly confined to Ce and La with a total of 63 and 55

reports,correspondingly,withminor informationavailable forGd (21)andNd (16),andsparse for theother

REEs,especiallyforHREEs:Y(15),TbandYb(8)(Figure2.8).Onemustnotethatthisgroupissignificanttothe

developmentandfabricationofproductssuchasmagnetsandphosphors(asseenaheadin2.5),henceforthwith

trueeffectrelatedtowork-relatedandenvironmentalexposures[31].

SeveralstudieshavedemonstratedthatREEshavestimulatoryorprotectiveeffectsonlowquantities,and

adverseeffectsathigherlevels.AsummarizingtableconcerningthetoxicityoftheREEsispresentinAnnexII–

TableII.1.

Figure2.8–Publishedarticlesreportingoneithertoxic(■)orstimulatory(o)effectsofindividualREE[31].

On the vicinity of a large-scale mining area located in Hetian town of Changting County, Fujian

Province,SoutheastChina,theconcentrationofREEsincultivatedsoilandvegetableswasanalysed,aswellas

in human hair and blood [30]. More than 50 rare-earth mining sites are dispersed throughout Hentain,

moreover,the town has a vast agricultural production representing, approximately, 17% of Chinas’ total

production.

ItwasdeterminedthattheFarmlandsinthesurroundingsarecontaminatedseriouslyduetoREEsmining

production, leading to various accumulation levels of REEs amongst vegetable species, as well as elevated

concentration of REEs in human hair and blood. Despite the concentration values, it was determined that

vegetable consumption would not result in exceeding the safe values of estimate daily intake ( 100 −

5Foreignchemicalsubstancefoundwithinanorganismthatisnotnormallynaturallyproducedbyorexpectedtobepresentwithin.

20

110𝜇𝑔𝑘𝑔34𝑑34)[30].However,onenotesthatattentionshouldbepaidtomonitoringthehealthofthepeoples

inminingareasowingtolong-termexposuretohighdoseREEsfromsoilandfoodcontamination.

2.5. REEsspecificationsanduses

REEs have been recognised as useful due to their chemical and physical properties; they are becoming

increasinglyimportantinthetransitiontoagreeneconomy.Thevarietyofhigh-techapplicationsofrare-earth

elementshasflourished,especiallygreentechnologiesandarmourindustry/defenceweaponsystems[18].They

areusedinmetallurgy,inelectronics,inchemicalcatalysts,asfluorescentsubstancesforcomputermonitors,

lampsandtelevisions,aswellasincatalyticconverters[26].

In a more precise description, REEs, have a crucial role in applications like permanent magnets, lamp

phosphors, catalysts, rechargeable batteries, automotive catalytic converters, wind power generators,

phosphorsforflatscreens,lightemittingdiode(LED)andcompactfluorescentlight(CFL),highstrengthmagnets,

chemicalsandpetroleumrefiningcatalysts,pharmaceuticalsandmetallurgicaladditivesandalloys[1,2].

Forexample,Ce,thedominantREE,isusedincatalyticconvertersincars(autocatalysts),permittingthem

torideathightemperatures;Laisusedincameraandtelescopelensesasglassadditives;Ndisusedtomake

powerfulmagnetsused in computerharddrivesp.e,making themsmallerandeffective, aswell as ingreen

technologies (inwindturbinesandhybridcars).Pr isused inmetallurgytocreatedurablemetals for aircraft

engines;Gd isused inX-ray,magneticresonance imagescanningsystems,andalso intelevisionscreensasa

componentofphosphors(Figure2.9).

Figure2.9–REEsingreentechnology(adaptedfrom[28]).

Eu,TbandYareimportantinmakingscreensfordeviceswithvisualdisplays,astheyareusedinmaking

materialsthatgiveoffdifferentcolours[32].

Table2.3sumstheREEsusageinseveralapplications.

21

Table2.3–Rare-earthsusagebyapplicationinpercentage[33].Percentagesareroundedtothenearestdecimal.Values

maynotaddtototalsshownowningtoindependentrounding.–noconsumption.

REO Catalyst CeramicsGlass

IndustryMetallurgy

Battery

alloys

Neodymium

magnetsPhosphors Other

Ce 32.2 12.0 65.6 52.0 33.4 - 11.0 39.0

Dy - - - - - 5.0 - -

Eu - - - - - - 4.9

Gd - - - - - 2.0 1.8 1.0

La 66.4 17.0 28.3 26.0 50.0 - 8.5 19.0

Nd 0.83 12.0 1.3 16.5 10.0 69.4 - 15.0

Pr 0.57 6.0 2.5 5.5 3.3 23.4 - 4.0

Sm - - - 3.3 - - 2.0

Tb - - - - 0.2 4.6 -

Y 53.0 0.8 - - - 69.2 19.0

Other - 1.5 - - - - 1.0

Table2.4–DistributionofREOsconsumptionbymarketsectorin2008[33].ValuesareinmetrictonsofREOs.

REO Catalyst CeramicsGlass

IndustryMetallurgy

Battery

alloys

Neodymium

magnetsPhosphors Other Total

Ce 8820 840 18620 5980 4040 - 990 293042

200

Dy - - - - - 1310 - - 1310

Eu - - - - 441 441

Gd - - - 525 162 75 762

La 18180 1190 8050 2990 6050 - 765 143038

700

Nd 228 840 360 1900 1210 18200 - 113023

900

Pr 152 420 694 633 399 6140 - 300 8740

Sm - - - 399 - - 150 549

Tb - - - - 53 414 - 467

Y 3710 240 - - - 6230 143011

600

Other - 480 - - - - 75 555

Total 27400 7000 28400 11500 12100 26300 9002 7500129

000

22

According to the Congressional Research Service, REEs not only are critical elements, but also ofmajor

importanceduetotheiruseinavarietyofdefencerelatedapplications,suchas:“finactuatorsinmissileguidance

andcontrolsystems,controllingthedirectionofthemissile;diskdrivemotorsinstalledinaircraft,tanks,missile

systems,andcommandandcontrolcentres;lasersforenemyminedetection,interrogators,underwatermines,

andcountermeasures;satellitecommunications,radar,andsonaronsubmarinesandsurfaceships;andoptical

equipmentandspeakers.”[18](Table2.5).

ThisleadstoanextensiveandrisingexplorationaswellasevaluationofREEsdepositsaroundtheworld.At

the same time, there is international concern about the security of their future supply, their costs, and the

impactsthismighthave.

Table2.5–Useofrare-earthelementsinavarietyofdefence-relatedapplications[18].

Technology Selectedexamples REEsused

Compact/Powerful permanent

magnets for guidance and electric

controlofmotorsandactuators

Tomahawk cruise missile; Smart

bombs; Joint direct attack

munitions; Predator unmanned

aircraft

Nd,Pr,Sm,Dy,Tb

Energy storage, density

amplifications, capacitance for

electronic warfare and directed

energyweapons

Jamming devices; Area denial

system; Electromagetic railgun; Ni-

Mbatteries;

Numerous

Amplification of energy and

resolutions for targeting and

weapons

Laser targeting; Air based lasers;

Laseravenger;Saber-shotdisruptor;

Vehicleswithlaserweapons

Y,Eu,Tb

Compact and powerful permanent

magnetsforelectricdrivemotors

Integrated starter generator; Joint

Strikefighter;

Hubmountedelectrictractiondrive

Nd,Pr,Sm,Dy,Tb

Amplification (enhanced resolution

of signals) for radars, sonar,

radiationandchemicaldetection

Sonartransducers,radar,enhanced

𝜆rayradiationdetector;

Multipurpose integrated chemical

agentalarm(MICAD)

Nd,Y,La,Lu,Eu

23

Chapter3. RecyclingofEOLproductscontainingREEs3.1. Introduction

Asanoutcomeofthesupplyrestrictions,REEshavebeenlabelledascriticalmaterials.Thesupply-demand

balanceisgenerallycharacterisedbyanunder-supply.Asstatedin1.2.1,thefiveREEscharacterizedascritical

areNd,Eu,Tb,DyandYforwhichdemandisexpectedtogrowbyupto30%inthenextyears[16].

Alternativesupplysources,asefficientrecycling,notonlywouldreducethe“REEscrisis”,butalsowould

allow theattainingofREEsconcentrates freeofexportation fees, thusbalancing thepricevolatility,balance

problemsandradioactivity,sincewewouldobtaintheminhigherpercentageandtreated.Longtermavailability

wouldbeassured.Eventhoughtherearemanyinvestigatedmethodsofrecyclingthataresuitedandproven.Until2011less

than1%oftheREEsentertherecyclingloop[1].

The low percentage is due to inefficient collection, lack of infrastructure, technological problems, low

concentrationsinscrap,badecodesign(doesnotallowefficientrecoveryattheendoftheirlife)and,mainly,lack

ofincentives[1].

Regarding technological problems one knows that REEs are normally recycled using routine recycling

techniquesdesignedforstandardmetals,whicharenotonlyoutdatedbutalso,don’ttakeintoconsiderationthe

propertiesofthematerials[16].

ScopeforrecyclingisalsolimitedbythefactthatthelikelyfuturedemandforsomeREEsislargecompared

totheamountalreadyincirculation,andbythelonglifetimesofsomeoftheproductsinwhichtheyareutilized.

At present, Japan is the only significant centre for research into recycling techniques, with Hitachi, for

instance,aimingtorecycleelectricmotormagnetsby2016[2].

AdrasticimprovementintherecyclingofREEsis,therefore,anabsolutenecessity.Thiscanonlyberealized

bydevelopingefficient, fully integratedrecyclingroutes,whichcantakeadvantageoftherichREEsrecycling

literature.

Alternativesupplyingincludes:urbanmining(useofspentproductsbyextractingmetalfromit),reuseand

recyclingi.e.secondarysuppliesandstockpiling(Figure3.1).Substitutetechnologiesareaviablealternativeas

well.

Whereas, certain goods containing REEs have a somewhat long longevity, as well as content to create

secondary supplies aswind turbines and permanentmagnets, others contribute to the opposing. Electronic

deviceshaveagreatlycurterlifetimethereforeresultinginaconstantneedtoproducenewsubstituteproducts.

ThecorrespondingdemandforREEsisnotmetbyurbanmining[16].Tobemoredetailed,a1,5MWwindturbine

usedaround350kgofREEs,whereasloudspeakersofasmartphoneuses50mgofNdand10mgofPr[16].

24

Figure3.1–Alternativesupplying:directrecyclingofpre-consumerscraporresidues;urbanminingofEOLconsumer

goodsandotherproducts;landfillminingoflandfilledpre-consumerandpost-consumerwastestreams(adaptedfrom[2]).

Takingthisintoaccount,someproducts,suchasthoseusedincatalysis,glassesandalloys,arenotrecycled

due to their limited quantity of REEs as well as separation issues. Regarding ceramics, phosphors and

batteries,technologyisnowadaysavailable[16],itfollowsthelifecyclepresentedinFigure3.2,wheretheyare

ideallyprocessedinordertoobtainREOsandmetals.

Figure3.2–LifecycleofREEsinmajortechnologicalapplications(adaptedfrom[2]).

Shortandlong-termimprovementswouldcontributetooptimisingrecyclingtoprovideancillarysupplyof

REEs. Since recycling consumes less energy and chemicals than mining, it would also bring environmental

benefits.

Intheshortterm,thecollectionofspentproductscontainingREEsneedstobefurtherimprovedintermsof

quantities.Separatedepositsforconsumergoodswouldpreventlosingthispotentialresource.

25

A longer term action is to establish a recycling economy. This includes, in particular, creating products

consuming as few REEs as possible and allowing as much dismantling and recycling as possible, as well as

strengtheningexistingeco-designprovisions.

3.2. RecyclingofREEsinlampphosphors

Asmentionedinthesubchapterabove“regarding(…)phosphors(…),technology isnowadaysavailable”.

However,intheparticularcaseoflightningapplication,where9upto12tonsofREEsareused[6,33],phosphor

recyclingispracticallynullinthespecificcaseofPortugal.Inthewholecountry,thereare750lampcollection

sitesand,accordingtoAMB3E,around70%oflampsarestillnotbeingcollected[34].Furthermore,ecotaxes

decreased from 0.23€/lamp to 0.07€/lamp in 2015which does cover the recycling costs [35]. On the other

hand,Spainhasmore than12000 collectionpoints andeco taxes for fluorescent lampsof 0.20-0.30€/lamp

[36,37].

TherecyclingpotentialofREEsinlampphosphorsisfoundinTable3.1.Theauthorscalculatedthepresented

values starting fromthe in-used stocks in2007and furthermore, taking intoaccount thegrowth rateof the

lightingapplications[2].

Table3.1–RecyclingpotentialsforREEsfromphosphors[2].

Application

EstimatedREEs

stocksin2020

(tons)

Estimatedaverage

lifetime(years)

EstimatedREEsold

scrapin2020(tons)

RecycledREEsin2020(tons)

Pessimistic

scenario

Optimistic

scenario

Lamp

phosphors25000 6 4167 1333 2333

Fluorescentslamps,likeservicelamps,compactlamps,tubularlamps,areonegroupofseveralphosphors-

basedproducts(Figure3.3).Theyuseamixtureofphosphorsinordertoproducethedesiredlight,themajority

ofmodernlamps,alsoknownastri-bandlamps,usesamixtureof3phosphors,red,blueandgreen,togenerate

whitelight[38,39].

REEs-based phosphors are favoured over halophosphors since these last comprise a blend that is less

efficientthusproducingalowerqualitylight.Regardless,halophosphorsarestillusedsincetheyproducecheaper

whitelightlamps[38,40],constitutinganimpurityintherecyclingperspective6[39].

Even though the phosphors content varies, not only frommanufacture to manufacture, but also from

applicationtoapplication,astandardtrylamphasaphosphorcompositionof:55%red,35%greenand10%blue

[38,39].

6Thepresenceoflargeamountsofcalcium,originatingfromhalophosphors,posesproblemsduringleachingbyincreasingacidconsumptionandlimitingthesolidtoliquidratio.LeachingofcalciumwithacidicsolutionsoccurssignificantlyfasterthanREEs,leadingtofastconsumptionofprotons.

26

Themainphosphorsbeingcurrentlyusedintheproductionoffluorescentlightsareclassifiedthroughthe

followingacronyms,accordingtothechemicalcomposition[2],[38–40]:theredphosphor𝑌,𝑂8: 𝐸𝑢8<(YOX),the

green phosphors𝐿𝑎𝑃𝑂@: 𝐶𝑒8<, 𝑇𝑏8< (LAP),(𝐺𝑑,𝑀𝑔)𝐵J𝑂4K: 𝐶𝑒8<, 𝑇𝑏8< (CBT),(𝐶𝑒, 𝑇𝑏)𝑀𝑔𝐴𝑙44𝑂4N (CAT) and

thebluephosphors𝐵𝑎𝑀𝑔𝐴𝑙4K𝑂4O: 𝐸𝑢,<(BAM) and 𝑆𝑟, 𝐶𝑎, 𝐵𝑎,𝑀𝑔 J 𝑃𝑂@ 8𝐶𝑙: 𝐸𝑢,<which is less common.

One of the author refers to two green phosphors which are similar to CAT and

CBT,respectively:𝐶𝑒𝑀𝑔𝐴𝑙4K𝑂4O: 𝑇𝑏8<and(𝐶𝑒, 𝐺𝑑, 𝑇𝑏)𝐵J𝑂4K[39].

Figure3.3– Fluorescentlampdiagramwiththemainconstituents.

Regardingtherecovery,onemustunderstandthecompositionoftheproductinhands.Atypicalcompact

fluorescent light consists of glass, metals (Al, Fe-Ni alloy), plastic, phosphor powder and mercury 7

representing,in weight, 88%, 5%, 4%, 3% and 0.005%, respectively [40, 41]. In order to obtain phosphors’

powder,apre-treatmentisaprerequisitetoseparatethemfromothercomponents.Crushingistypicallyused

(asthecaseofthesamplesusedintheexperimentalworkofthisthesis)tobothreducethevolumeandpart

macro-fractions.Thefinefractionismorerichinphosphorpowder,butstillcontainsconsiderableamountsof

glass,thusresultinginsomedilutionofitsREEcontent[2].

Aftercrushingandsievingofthelamps,thephosphors’wetsludgecontains,typically,45%ofhalophosphate

phosphor,20to30%ofglassandsilica,12%ofaluminaand10to20%ofREEphosphors.Residualfractionare

alsopresentsintheorderof5%[40,41].Therelativelyhighcontentinbothsilicaandaluminaarisesfromthe

existingbarrierlayer[2,40].Thisbarrier,placedin-betweenthephosphorlayerandtheglasstube,protectsthe

7Althoughmercury is alsoametal, adistinction ispurposelymade since, in the caseof fluorescent lamp recycling,

mercuryisahazardousimpurity,unliketheothermetalspresent.

27

glassenvelopeagainstmercuryvapourpreventingHgOdepletion,improvingthelampefficiencybyreflectingUV

thatpassesintotheglasslayer[2,40].

Sincethereisalwaysmercuryintheseparatedfractions,adecontaminationistypicallycarriedoutthermally,

sinceitwasconsideredtobewaymoreefficientthanwetdecontaminationsanddoesnotcauseREEs’losses

[39].Itcanbeeitherdonepartly(400-600°Cinvacuum)ortotallybyusinghighertemperatures(800°C)[2].Its

presencecomprisesnotonlyahazard,sinceitistoxic,butalsoanimpurityforthesolventextractionoperations.

Even though regulations require amaximum of 3.5mg/lamp, old lamps are still being processedwhose

mercurycontentedvaries, inageneralperspective,between0.72mg/lampto115mg/lamp[2].Furthermore,

HgOtendstochemicallybondtothephosphorsparticlesgradually.ThusinanEOLlamptheamountofmercury

cancomeupto40timeshigherthaninanewlamp,comprisingmorethan85%ofthemercuryinthelamp.

Thelampphosphorscontainamaximumof,approximately,28%,inweight,ofREOsyetonly10%ofwhich

is truly recycled [2, 41]. In fact, in most countries, after the stabilization (or partial removal) of mercury,

phosphors’fractionsareeitherlandfilledorstoredincontainers.

TherearethreeroutesregardingtherecyclingofREEsfromphosphorsinfluorescentlamps[2,40],itcanbe

doneeitherby re-utilizationof theelements,or theREEscanbeseparated into individual rare-earthmetals

(REMs)forfurtherapplications:

1. Directre-use;

2. Separationofphosphormixtureintodifferentcomponentsbyphysicochemicalseparationmethodsfor

re-useinnewlamps;

3. RecoveryofREEscontentbychemicalattacks.

Second and third options use very similar hydrometallurgical processes to the primary extraction ones:

leaching,precipitationandsolventextraction.Leachingistheprocessofextractingconstituentsfromasolidby

dissolvingtheminaliquid,inthisparticularcaseisusedtoremovemetalsfromthesolidphaseintheformof

solublesalts.Precipitationconsistsonachemicalreactionbetweensolutionsresultingintheprecipitationasolid

(forexample,𝐴𝑔𝑁𝑂8 + 𝐾𝐶𝑙 → 𝐴𝑔𝐶𝑙 ↓ +𝐾𝑁𝑂8).Finally,thesolventextractionmethodallowstheseparation

ofcompoundsbasedonthesolubilityofthedifferentelementsintwoimmiscibleliquids,usuallywater(polar)

andanorganicsolvent(non-polar).

Nevertheless,thebehaviourofthedifferentphosphorstostrongacidchemicalattacksvariesbroadly.For

instance,YOXcanbedissolvedinmildacidic/dilutedsolutions,butLAP,CATandBAMaremoreresistantthus

needingadifferentapproach[2,39].Therefore,oneofthefocalchallengesisobtainingabsolutedissolutionof

theREEswhenleached[39].Somestudiesindicatethathydrochloricacidshowsbetterresultsintheleaching

process[42].

Someexamplesofprocessesareshowninthefollowingtables(Table3.2andTable3.3).Othershavealso

beendeveloped,asmentionedinliterature[2,38,39],andevenpatented[43,44].

Notwithstandingthenumberofpapersandstudies,pilot-scaletestsareinfrequent.Likewise,aredeveloped

atlab-scaleand,sometimes,withartificialand/orpurephosphormixtures.

28

Table3.2–PublicationsregardingtheleachingofREEsfromlampphosphors(adaptedfrom[38]).

Table3.3–PublicationsdealingwithseparationsofREEsfromlampphosphorsbysolventextraction(adaptedfrom[38]).

Material ExtractionSystem Extractionconditions Efficiency(%) Reference

Powde

rfrom

fluorescentlamps

TBPcomplexeswithHNO3

Patm;50℃;

120min.

37.4(Y)36.8(Eu)

<3(La,Ce,Tb)[51]Supercritical

CO2;60℃;15MPa

99.7(Y)99.8(Eu)

<7(La,Ce,Tb)

Real

fluorescent

lampwaste

leacha

tes

Trimethyl-benzylammoniumchloride 80℃ 98.8(Y)96.5(Eu) [46]

Lamp

phosph

ors

leacha

tes

N,N-dioctyldiglyocolamicacidintheionicliquid1-butyl-3-

methylimidazoliumbis(trifluoromethylsulfonylimide)

Batchtests:pH3

Declineinextractionabilityafterfiveextractioncycles.

[49]

Material

LeachingConditions Leachingefficiency(%)

ReferenceReagents T

℃t(h)

S:Lratio Eu Y La Ce Tb Gd

Fluo

rescen

tlam

pwaste

fractio

ns 25%v/vCH3COOH 20 168 1:10 50 75 2-10

[45]0,5M,1M,2M,4MHCl0,5M,1M,2M,4M

HNO320 168 1:10 >95 >97

Phosph

orsfromEOL

fluorescentlamps 3M+5MHCl 60 4+3 1:10 97.38 99.06 98.22 98.15 [42]

MixedHNO3+H2SO4(4Meach) 125 4 92.8 96.4 [46]

2MH2SO4 37 8 1:50 71.5 75.3 61.1 66.9 [47]2MH2SO4 90 3 1:5 90 [48]

Variousacidicsolutions 70 6 1:20 >85 >91 [49]

4MHCl 60 1 1:10 96.28 [50]

29

Chapter4. ExperimentalA representative 18L sample of REE richmud, resulting from the physical-chemical treatment of spent

fluorescentlamps,wascollectedfromAMBICAREINDUSTRIAL–TratamentodeResíduosS.A.facility,locatedin

ParqueIndustrialdeMitrena,Setúbal,Portugal.ThesamplewaskeptinaPVCtank.AMBICAREprocessesvarious

typesoffluorescentlampsinlargebatches(500kg),simultaneously.Crushingiscarriedoutinawatersolution

and a rotary screener is used to separate macro-fractions (glass and steel fragments) from a fine fraction

containingthepowderphosphors,increasingtheREEscontent.

A strong oxidation product is utilized during the crushing in order to oxidize elementalmercury and to

stabilizeit.Duetothenatureoftheprocess,separationofpurephosphorspowderisnotpossible.

Theresultantphosphorwetsludge(approx.30wt%moisture)comprises,typically,45%ofhalophosphate

phosphor,20to30%ofglassandsilica,12%ofaluminaand10to20%ofREEsphosphors

Thepurposeofthisworkisto:

• Characterize (physically, chemically, structurally and morphologically) the lamp waste fraction by-

productinordertofinditspossibleapplications;

• Assess the applicability of a recovery, via physical-chemical processes of REEs from the waste at

laboratoryscale,usingacidleachingoperations.

TheoverallexperimentalworkgoesasexplicatedinFlowchart4.1:

Flowchart4.1–Setupfortheexperimentalworkfortreatmentoflampwaste.LettersA-D,redirecttootherflowcharts

explainingeachstepoftheexperimentalprocedure.

The initial phase of the experimental work process consists on obtaining several types of samples by

samplingthe18Lsludgeinordertoobtainbothdryandwetsamplesforfurthercharacterization,analysisand

processing.ThesamplingprocessgoesaccordingtoFlowchart4.2.

30

Flowchart4.2–Samplingandphysicalprocessing.

31

Inthesamplingprocesstwowayswereconsideredsince,oncethetankwasopened,therewasaseparation

betweenapulpandaliquid.Foreachphasedifferentmethodologiesweretakenintoconsideration.

Forthesupernatantliquidthefollowingstepsweremade:

1. FilterthesupernatantliquidwithaBüchnerfunnel;

2. Measurethevolumeandmassofthefilteredliquid;

3. Prepare3sampleswiththeliquidforfurtheranalysis(SL.Xsamples):

a. pHdetermination;

b. densitycalculation.

4. Weightthesupernatantpulp,resultingfromfiltration–SPsample;

5. Dry in the oven at 50°C the SP sample until constantweight is obtained, for the determination of

humidity.

6. RemovalofthetoplayerofdriedSPsample–TL.Xsamples;

7. SievingofdriedSPsample,separately,witha0.315mmsieve–IS.Xsamples;

8. Homogenizationandseparationofinfra0.315powdersintherotationalsampler–P.Xsamples;

Theremainingproductinthetanksufferedadifferentprocess,asfollowing:

1. Sieving(3.15mmsieve)thewetsludgewhilstpouringintotherotationalmoulding–IL3.15;

2. Homogenization and separation in the rotational sampler: divide into the eight flasks and pour in

containers,repeatedlyuntiltheallsampleisdivided–Lsamples;

BothwetanddrysampleswillbeobtainedfromLsamples.Regardingtheattainmentofthedrysamples

onemustfollowthesamestepsastookinwiththeSPsamples:

3. Drying in the oven at 50°C of samples L1, L12 and L19, until constant weight is obtained, for the

determinationofhumidity;

4. Removalofthetoplayerofeachdriedsample–TPsamples;

5. Sievingofeachdriedsample,separately,witha0.315mmsieve–IS.Xsamples;

6. Homogenizationandseparationofinfra0.315powdersintherotationalsampler–P.Xsamples;

7. Mixtureofca.70gofeachP.X.sample;

8. Homogenizationandseparationofsamples’mixtureintherotationalsampler–PGsamples;

Forthesmallerwetsamples,onemust:

9. MixtureofsamplesL2,L11andL20;

10. Sievethewetsludgewhilstpouringintotherotationalsampler(0.315mmsieve)–IL0.315samples;

11. Homogenizationandseparationintherotationalsampler–LG.1sample;

12. Homogenization and separation in the rotational sampler of one wet global sample type 1 – LG.2

sample;

32

Itcanbepointedoutthatseveralsampleswereproduced.Inordertofacilitatethereaders’interpretation,

thelettersusedtonamethesamplesareacronymsofthesamplestype/nature,asexplainedahead.

Thefiltrationofthesupernatantliquidresultedinafilteredsupernatantliquidandinpulp,thusproducing

3SL.XsampleswhereX=1,2,3,aswellasoneSPsample.Fromtheseparationofthewetsludge24samples

wereproduced:L.Xsamples,whereX=1,2,…,24.Inthesievingoperations,supramaterialworksasimpurities

hencecreatingtheIsamples.Whensievingadriedsolidmaterial,thenIS.Xisusedtonameit.Ifthesampleisa

wetsludgethenisnamedILfollowedbythesievemeshsize,p.eIL3.15ifa3.15mmsieveisused.Thedryingof

L1,L12,L19andSP,resultedintoplayersamples(TL.Xsamples),powdersamples,P.XsampleswhereX=1,12,

19andSPinbothcases,aswellasdryglobalsamples(PGsamples).Wetglobalsampleswereproduced,named,

LG.1andLG.2samples,werethelatestismorehomogenized.

Theresumeoftheseveralsampledesignations,fromthesamplingprocess,arepresentinTable4.1.

Table4.1–TypesofSamples.The“X”codeimpliesthereareseveralsampleswithinagroup.Furthermore,thevaluetaken

bytheXsisrelatedtotheLsamplesifX=number,ortothepulpifX=SP.

Nameofthesample Designatedmaincode DesignatedXcode

FilteredSupernatantLiquid SL.X X=1,2,3

SupernatantPulp SP –

ImpuritiesPulpsievedsample

Supra3.15mm IL3.15 –

Supra0.315mm IL0.315 –

Drysolidsievedsample Supra0.315mm IS.X X=1,12,19,SP

“Liquid”-Sluge L.X X=1,2,…,24

“Liquid”GlobalType1 LG.1 –

“Liquid”GlobalType2 LG.2 –

TopLayers TL.X X=1,12,19,SP

DryPowder P.X X=1,12,19,SP

DryPowderGlobal PG –

SamplesP.X(allfour)andPGwerefurtherdividedinto8smallplasticbags(usingtherotationalsampler),to

facilitate the use of the powders in the following steps. However, a code was not created for each of the

bags,beingnamed1st,2nd,….,8thinthetablesahead(Table5.3andTable5.5).

Somesampleswereproducedwithoutadetermineduse:supraimpurities,top-layersandthesupernatant

liquid. Supra samples were produced since thematerial presented numerous impurities (glass, caps, wires,

amongst others). The top-layers were removed since, when the material was dried, the surface became

extremelydarkerthantherest.Finally,thesupernatantliquidwasfilteredandputaside.

All these sampleswere supposed to be further characterized, otherweighing and/or pHdetermination,

however,duetotimecomplications,itwaspostponedtoafuturework.

33

Asimplifiedschemewasmadeinordertoillustratehowthemainsamples(theonescharacterized)were

collected,regardingtheinitial18Lsample(Figure4.1).

Figure4.1– Simplifiedsamplingdiagram.

Characterizationoccursnextforbothwetanddrysamples:

• Granulometryanalysisinthelaserdiffractiongranulometer(CILAS1064)ofsamples:P.1,P.12,P.19,

PG,L3,L13,L21andLG.1(performedinLNEG);

• StructuralcharacterizationbyX-RayPowderDiffraction(XRPD)(PanalyticalX´PERTPRO)ofsamples

P.SP,P.1,P.12,P.19andPG(performedinLAMPIST);

Thediffractogramswereobtainedbyapplyingthefollowingparameters:

• Position4.9751≤ 2𝜃 ≤79.9751,withstepsize2𝜃=0.0500;

• ScanStepTime[s]=99.4293;

• RadiationK-Alpha1[Å]=1.54060fromaCuampoule(anodematerial);

• GeneratorSettings=35mA,40kV.

• Morphologicalcharacterizationby:

a. StereoZoomMicroscope(OlympusSZ61withmicroscopecameraMOTICAM10Mp)ofP.SP,

P.1,P.12,P.19andPG(performedinLAMPIST);

b. Scanning Electron Microscope/Energy Dispersive Spectroscopy (SEM/EDS) (FEG-SEM: JEOL

7001F)ofsamplesP.SP,P.12andPG(performedinMicroLab).Eachonewasmetalizedusing

goldandpalladiumfilm(15nmthick),inordertomakethesamplesconductive,andthenplaced

inaaluminiumsampleholder;

• ChemicalelementalanalysisbyInductivelyCoupledPlasma–AtomicEmissionSpectrometer

(ICP-AES)(JYULTIMA)ofliquorsamples(directanalysisafterdilution)andofSLsample(performed

inRequimte).Forsolidsamplesanalysis,apreviousdigestioninaquaregiawasmadetosolubilise

themetalsinsolution(samplesAR1andAR2).Thedigestionprocedurewascarriedoutbeattackof

1gofpowderwith40mLofaquaregia(1:3ofnitrictohydrochloricacid)at80°C,for3h;

Thefollowingstepoftheexperimentalprocedureistheleachingprocessthatgoesintwoseriesoftests,as

follows(Flowchart4.3andFlowchart4.4).

34

Flowchart4.3– Firstseriesofleachingexperiments(1and2)todetermineparametersthatallowmorerecoverypercentage

Inthefirstseries(experiments1and2)severalcombinationsofconditionswereconsidered(Table4.1),in

ordertodeterminefurtherconditionstoexplore.HClwasalwaysusedasleachant.

Inthesecondexperiment,eventhoughtheleachingparametersaresimilar(Table4.2)calcination8isdone

primarily,untilconstantweight,sinceitmightresultinthebreakageofthephosphates(LAPandhalophosphate

phosphors)intooxides,thusfacilitating/increasingtheleachingefficiency.

Table4.2–Determinedleachingconditionsforexperiments1and2.

Experiment LeachingConditions

1 𝑡\]\^_=6h

T=90°C4MHCl

0.5MHCl

T=25°C4MHCl

0.5MHCl

2 𝑡\]\^_=6h T=90°C 4MHCl

The following experiments (3 to 6) (Flowchart 4.4) were performed, after the results of the preceding

ones,andaimedattestingalternativeleachants(HNO3andH2SO4)orcombinationsofthem.Hydrochloricacid

waschosen toperformthe firstacid leaching (inexperiments3,4,5), since it showsbetter leaching results,

accordingtoliterature[42].SeveralauthorsexploredtheuseofHNO3andH2SO4.However,thelatestisused

highquantities(18M).InsteadofleachingaconcentratedH2SO4digestion9,wasthought,wherelessvolumeof

acid is used, as well as higher temperatures. In this case, a subsequent water leaching operation was

implementedinordertosolubilizethemetalsthatweretransformedtosulphatesduringthedigestion.

8Calcination isasathermaltreatmentprocess intheabsenceor limitedsupplyofairoroxygentobringaboutathermaldecomposition.Normally isperformedwithtemperaturesin-between500and1000°C,howeveranauthordemonstratedgoodrecuperationresultsbyusinganaidingcalcinationwith200°C.Hence,theoptionwastested.9Thechoiceofacidresultsfromthefactthattheotherstudiedacidsarenotstableathightemperaturesanditismoresecuretoworkwiththemdissolvedinsteadofconcentrated.Thisprocessworksinthesamebasesoftheleachingprocess.

35

Inleachingprocesses,samplesweretakenafteroneandsixhoursofreaction,inordertodoso,3mLare

centrifugedandthen2mLofwhicharediluted10timesandsentforanalysis.

Allreagentswereofanalyticalgrade.Demineralizedwaterwasusedtopreparesolutionsfortheleaching

testsandforallanalyticalprocedures.Theleachingbehaviourofmetalswasstudiedusingalwaysasolid-liquid

ratio(S:L)of10%w/vi.e.foreach5gofsolid50mLofliquidneedtobeused.

Table 4.3 presents the process conditions for the second set of experiments. The samples from all the

experimentsarenotnamed,sinceitdoesnotinfluencethediscussion.

Flowchart4.4–Secondseriesofleachingexperiments,withalternativeacidcombinations.

Table4.3–Determinedleachingconditionsforexperimentsthreetosix.

Experiment ProcessConditions

3Leaching 𝑡\]\^_=6h T=90°C 4MHCl

Calcination 𝑡\]\^_=3h T=200°C

4 Leaching𝑡\]\^_=6h T=90°C 4MHCl

𝑡\]\^_=6h T=90°C 5MHNO3

5

Leaching 𝑡\]\^_=6h T=90°C 4MHCl

Digestion𝑡\]\^_=3h T=90°C 1.1mLH2SO4/g

𝑡\]\^_=6h T=40°C 1MH20

6 Digestion𝑡\]\^_=3h T=90°C 1.1mLH2SO4/g

𝑡\]\^_=6h T=40°C 1MH20

36

Chapter5. ResultsHereafter the various series of tests that had been performed are related and the results obtained are

presented.

5.1. SamplingandPhysicalProcessing

Fromthefiltrationofsupernatantwereobtained680mLofliquid(whichwasdividedinto3SLsamples)and

1052.6gofwetsludgethatwasthendried.Theseresultsdonotrepresentthe2Lofafloatsincepartoftheliquid

samplewas returned to the initial vessel, given the consistency of the pulp in the bottom and difficulty in

removingit.

𝑉ab = 680𝑚𝐿 = 680𝑐𝑚8;𝑚ab = 679.1𝑔 → 𝜌ab = 0.9987𝑔𝑐𝑚8 ; 𝑝𝐻 = 9.92

𝑚al = 1052.6𝑔

Regardingtheremainingmudinthetank,whenthehomogenizationwasperformed,a3.15mmwasused

sincethesamplehasseveralimpurities(Figure5.1).Theimpuritiesarecrushedmetal,glassandplasticpartsthat

passedtherotationalsieve.

𝑚nb8.4J = 57.2𝑔

Figure5.1–IL3.15sample.

Aftersuccessivedivisionsthroughtheeightvialsofthesampler,thehomogenizedandsievedpulpwassplit

intwenty-foursamples(numberedfrom1to24)placedintoindividualcontainers(L.Xsamples).

Thefirsttestsaimedatthecalculationofmoistureinthewetpulps.Foursampleswereused:oneresulting

fromthefiltrationofthesupernatantliquid,i.e.SPsample,andthreefromthehomogenizedandsievedpulp

from the tank (L1, L12, L19). Samples 1, 12 and 19 representing the top,middle and lower part of the 18L

container.Theirinitialweight(priortodryingprocess)where:

𝑚b4 =1688.7g;

𝑚b4, =1497.7g;

𝑚b4N =741.7g.

37

Allsampleswereweighedintwosituations:freshfromtheovenintheoriginalcontainerandafteronehour

ofbeinginadesiccator,afterbeingtransferredtotwogobletseach.Thereasonofthetwoweightsarisesfrom

thefactthattheoriginalcontainersdidnotfitthedesiccator,sowhenthetransfersisdone,masslosswould

arise.Thecoolinginalowhumidityenvironmentpreventshumiditytoenterthesamples.

ThecalculationsforthemoisturecontentofsamplesSP,L1,L12andL19arepresentedinAnnexIII.Onlythe

finalmoisturecontentsarepresentedinthissub-chapter,aswellasthemassbalancethroughoutthesampling

andphysicalprocessing.

Fromtheobtainedmoisturecontentonecaninferthatthepercentageofwaterisapprox.30%(Table5.1).

Itwasexpectedthatthesampleswillhavelesswatercontentastheyareremovedfromtop-downfromthe

sampletank.Howeversomeincreasesinvaluewereobserved.TheincreaseinmoisturecontentfromsampleSP

toL1probablyarisesfromsurfacedisturbance;theaugmentationfromL12toL19isduetotheadditionofwater

madeforbettersludgehandling.

Table5.1–MoisturecontentofsamplesSP,L1,L12andL19.

Sample MoistureContent(%)

SP 31.27

L1 32.1

L12 28.3

L19 29.1

Sincetheoriginaldrysampleswereseparatedintogoblets,themakingoftheP.Xsampleswasmadewith

onlypartofthetotaldrymass,regardingonlyonegoblet(whichmassispresentedinthecolumn“Goblet”in

Table5.2).

Table5.2presentstheevolutionoftheweightofthesamplesintheproductionofthedrysamples,untilthe

attainingoftheinfra0.315mmpowders.

Table5.2–Masslossintheproductionofthedrysamples.Massisexpressedisgrams(g).

Samples WetweightDryweight Masslost

(fortotaldrymass)IS.X TL.X Infra0.315mmpowder

Total Goblet

SP 1052.6 723.5 165.7 329.1 4.3 9.6 145.9

1 1688.7 1143.9 604.1 544.8 7.7 17 564.9

12 1407.7 1008.8 470.5 399.7 8.4 14.9 335.7

19 741.7 525.5 254.7 216.2 10.9 9.7 233.6

Aftertheremovalofthetoppartandsupra0.315mm,theinfra0.315mmpartsweredividedintotheeight

P.X samples each (Table 5.3). Afterwards, all type P.X samples numberedwith number 1, originated the PG

samples.

38

Theuseoftherotationalsamplerresultsinmasslosses,sincethemachinecannotbeproperlycleaned.In

betweentheP.Xsamples,themachinewasbrushed,aspartofthemassthatwasabletobereleased,itwas

addedtothepreparationoftheglobalsample.

Table5.3–Weightofthe32P.Xsamples,togetherwiththemasslossoftheprocess.Massisexpressedisgrams(g).

Sample 1st 2nd 3rd 4th 5th 6th 7th 8th Total InputMass

loss

P.SP 18.7 17.9 18.1 18.2 18.2 17.5 17.7 17.3 143.6 145.9 2.3

P.1 70.7 72.1 69.1 72.8 69.2 69 71.4 69.5 563.8 564.9 1.1

P.12 41.9 40.5 41.2 41.5 40.8 41.3 41.3 40.7 329.2 335.7 6.5

P.19 28.3 28.6 28 30 28 28.4 28.6 29.7 229.6 233.6 4

PG 20.4 20.8 20.3 20.4 20.7 20.7 19.9 21.2 164.4 159.6 -4.8

ForthepreparationoftheLGsamples,theprocessstartedwithtypeLsamplesclosetotheonesusedto

producethedrysamples(numbers2,11and20).Somemasswaslostwhilepouringintotherotationalsampler,

andagainwhenproducingbothwetglobalsamples(i.e.pouringfromtherotationalsampler’sflaskintothefinal

container).

Table5.4–MasslossintheproductionoftheLGsamples.Massisexpressedisgrams(g).

Samples Lsamplemass VolumeofsupernatantliquidinLsample Pouredmass Masslost

2 1753.7 53 1743.1 10.6

11 1475.4 52 1457.2 18.2

20 752.7 29 739.4 13.3

Total 3981.8 134 3939.7 42.1

LG.1sample isobtainedfromthemixtureof thethreeLsamples,summinga totalof3939.7g (as initial

weight).TheLG.1encodedwithnumber1wasusedtoproduceLG.2,asmentionedin0.

Table5.5–WeightoftheLGsamples,togetherwiththemasslossoftheprocess.

Sample 1st(g) 2nd(g) 3rd(g) 4th(g) 5th(g) 6th(g) 7th(g) 8th(g)Total

(g)

Input Mass

loss

LG.1(sampler’sflask) 437.1 436.8 459.5 462.9 457.4 424.1 452.5 444.4 3574.7 3939.7 365

LG.1(finalsample) 426.3 424 444 450.1 441.8 411.8 440.9 429.5 3468.4 3574.7 106.3

LG.2(sampler’sflask) 67.6 66.2 63.9 60.3 64.6 65.4 70.7 67.7 526.4 426.3 -100.1

LG.2(finalsample) 57.2 57.2 55.1 50.1 54.7 54.9 57.3 53.1 439.6 526.4 86.8

39

ThemasslossinthepreparationofLG.1samplesresultsnotonlyfromthemassretainedinthe1.12mm10

sieve(𝑚opqr^4.4, = 2.6𝑔),butalsofromthemassthatwasentrappedintherotationalsampler,aswellasthe

lossfrompouringfromthesampler’sflasksintothefinalflaks(106.3g).

Itisnoticeable,oncemore,thatwhilepreparingthelastgroupof8samples,therewasanincreaseinmass,

eventhoughwhilstpouringintothefinalsamplecontainerthereisalossof86.8g.Unlikethepreparationofthe

PGsamples,thesamplerwasnotcleanedinbetweenPG.1andPG.2,sincetheybothcomprisedamixture.So

partoftheentrappedmasshasfallenintothesampler’sflaks,100.1gtobeprecise.

5.2. Characterization

5.2.1. GrainsizemeasurementbyLaserDiffraction

Ithastobenoted,first,thatthetechniqueusedhasanabilitytomeasurefineparticles(0.04–500.00𝜇𝑚).

ThetestedsampleswereP.1,P.12,P.19,PG,L3,L13,L21andLG.1.

Thepulpsamples(L3,L13andL21)wereobtainedbyseparatingtheinitialsample(with18L),whichpassed

througha3.15mmsieve, into24samples.Assuch, inthecaseofthesesamples, theyareknowntocontain

particlessmallerthan3150𝜇𝑚(orinfra3.15mm).Onanothernote,theoverallwetsample(LG)wasmadefrom

pulpwhichwasfurtherpassedthrougha1.12mmsieve(asmentionedinthefooterabove),thereforeonecan

infer that, the particles present, are smaller than 1 120𝜇𝑚,which almost fits in the resolution of the laser

equipmentused.Finally,whenthepowdersampleswereprepared,thedriedpulpwassievedthrougha0.315

mmscreen,sotheparticlesareinfra315𝜇𝑚,thusfittingtheresolutionoftheequipment.

In short, the granulometry only measures the fine component of samples L3, L13, L21 and LG.1, but

comprises100%oftheparticlesintheremainingsamples.

Onecannotethatthereisfewdifferencein-betweenthefinestofparticles(Table5.6).

ThevaluesofD10indicatethat10%ofthevolume(ormass)ofthepowderfractionhasvalueslowerthanthe

onepresentedinthetable,whereasD90indicatesthat90%ofthemass’averagemaximumdiameter.Regarding

thetopoftheinterval,thereismorevariationinsize,asitcanbeseenbythedeviationvaluesi.e.SD.

Inaverage, the fractionconsistsofparticleswith𝜙 < 45.37 ± 13.80𝜇𝑚ifweregardonlythesludgeor

with𝜙 < 73.46 ± 16.21𝜇𝑚consideringonlythepowdersamples.So,onageneraloverview,theparticlesare

finer in thewet samples than in thepowder samples.A reason for thisbehaviourcanbe relatedwith some

agglomerationoftheparticlesduringthedryingprocess.Itcanalsobepointedoutthatthedeviationsfoundin

theD90diameterareclearlyhigherthanfortheothercharacteristicdiameters,sincelargeparticlescontained

someamountofimpuritiessuchasglassfragmentswhichgivesmoreheterogeneitytothosecoursefractions.

Furthermore,thelowervaluesintheliquidsamplesarisefromthefactthatthesupernatantliquidwasusedfor

themeasurement.Sothebiggest,thusheavierparticleshavealreadybeenprecipitated.

10In0,theexperimentalstatesthatthepreparationofLG.1sampleswasobtainedbysievingthewetsludge,whilstpouringintothe

rotationalsampler,througha0.315mmsieve.However,theprocesswasratherslow,soa1.12mmsievewasusedinstead.

40

Table5.6–ParticleSizeDistribution-D10,D50&D90-SieveAnalysis.AM–arithmeticmean;SD–standarddeviation.

5.2.2. X-RayPowderDiffraction

Onlythedrysamples(P.SP,P.1,P.12,P.19,PG)wereanalysedbyX-RayPowderDiffraction(XRPD).

XRPDisatechniqueusedfordeterminingthestructureofcrystallinephasespresent.AnincidentX-Raybeam

diffracts,duetothecrystallineatoms/molecules,intomanyspecificdirections.Theangleandintensityofthe

beamsisthencorrelatedtoaspecificstructure.

However,differentmaterial canhave the same lattice system, crystal familyor crystal structure. Lattice

substitutionscanalsochangetheanglewheresomereflexionsoccurduetothevariations in the interplanar

spacings.Forinstance,diamond,α-germanium,havebothadiamondcubiccrystalstructureAnnexI–TableI.1

presents several structureswhere solid substitutionsoccurs, namely: allanite,bastnäsite, loparite,monazite,

parisiteandsynchysite.

Theprecisechemicalcompositionofthephasesisnotpossibletodo,duetotheextensivesolidsubstitution.

Nevertheless, as mentioned EOL fluorescent lamps are a source of HREEs i.e. the lamp phosphor fraction

contains:La,Ce,Eu,Gd,TbandY.Therewillbealso,inlargeconcentration,Al,Si,P,Caandinsmallerquantities

Ba,Sr,Mg,Mn,Sb,Cl,F,Hg,PbandCd[2],[38].

Sample D10(𝜇𝑚) D50(𝜇𝑚) D90(𝜇𝑚)

P.1 1.98 11.04 55.40

P.12 2.48 13.55 91.21

P.19 2.63 13.14 82.18

PG 1.83 11.22 65.03

AM 2.23 12.24 73.46

SD 0.39 1.29 16.21

L3 0.96 6.95 28.16

L13 1.59 9.99 46.70

L21 1.45 10.44 61.90

LG.1 1.44 9.90 44.73

AM 1.36 9.32 45.37

SD 0.28 1.60 13.80

41

Figure5.2–XRPDpatterns(Intensityvs2𝜃)forthedrysamplesanalysed.Fromtoptobottomorder:P.SP,P1,P12,P19and

PG.

It can be concluded from Figure 5.2 that the same set of crystal structures are present in all the

samples,sincethesamepeakpatternispresent.

Themaingraphic,withtheanalysedview,obtainedisfeaturedinFigure5.3andthestructuresidentifiedin

thepatternlistinTable5.7.

Table5.7–NameofthecompoundsidentifiedbytheXRPDtechnique11.

Ref.Code Score CompoundName Displacement[°2Th.] ScaleFactor ChemicalFormula

00-005-0574 57 YttriumOxide -0.056 0.979 Y2O3

00-009-0432 48 Hydroxyapatite,syn 0.078 0.347 Ca5(PO4)3(OH)

00-004-0612 22 Monazite -0.060 0.065 (Ce,La,Y,Th)PO4

00-032-0199 31 Monazite-(Ce),syn -0.009 0.225 CePO4

00-042-1468 19 Alumina 0.030 0.189 Al2O3

11Thescalefactorisanarbitraryvalueusedtoadjusttherelativecontributionofindividualphasestotheoveralldiffractionpattern.

Thescorerepresentsthenumberofpeaksassociatedwiththeidentifiedstructure.

42

Figure5.3–XRPDpattern(Intensityvs2𝜃),with40 < 2𝜃 < 60.Thephase(s)ofthecompoundscorrespondenttothepeak

is(are)identifiedbythesymbols:p-YOX;¿-Monazite;�-Hydroxylapatiteand¢-Alumina.

Figure5.4–XRPDpattern(Intensityvs2𝜃),with60 < 2𝜃 < 80.Thephase(s)ofthecompoundscorrespondenttothe

peakis(are)identifiedbythesymbols:p-YOX;¿-Monazite;�-Hydroxyapatiteand¢-Alumina.

Correlatingtheidentifiedphaseswiththeknowphosphorsused,onecansaythattheexistenceofyttrium

oxideimpliestheexistenceofYOXphosphor(𝑌,𝑂8);thestructureofhydroxyapatitecanberelatedtotheblue

43

phosphor 𝑆𝑟, 𝐶𝑎, 𝐵𝑎,𝑀𝑔 J 𝑃𝑂@ 8𝐶𝑙 since both are part of the apatite group, the 𝑂𝐻3 ion(in the

hydroxyapatite)canbereplacedbychloride,producingchlorapatite,i.e.thereferredphosphor.Themonazite

structure,whichcanalsohavesubstitutingelementsinthestructuresuchasCeinsteadofLa,comprisestheLAP

greenphosphors(𝐿𝑎𝑃𝑂@).Thepresenceofaluminaisexpected,asmentionedin3.2,duetothebarrierlayerin

thelamp.

Othercrystallinephasesshouldberecognisedbythetechnique.Thenon-identificationsuggeststhatmaybe

theyareinmuchlowerconcentration.

5.2.3. ScanningElectronMicroscopy

Thedrysampleswerealsocharacterizedbyscanningelectronmicroscopy.Inthiscase,onlysamplesP.SP,

P.12andPGwereanalysed.

Thesamplesareratherheterogeneousbothinparticleshapeandparticlesize;phosphors,inparticular,seem

toformaggregatesofseveralparticles(Figure5.5,Figure5.6andFigure5.7).

Figure5.5–SEMmicrographofP.12sample(200x).

Figure5.6–SEMmicrographofPGsample(200x).

SampleP.SPwasanalysedbyEDS,inordertodeterminetheconstituentsofeightselectedparticles(Figure

5.7).Lanthanumandterbiumwereonlydenotedinthissample.Thisfactdoesnotinferthattheyarenotpresent

intheremainingsamples.Onemustnote,again,thatthesamplesareveryheterogeneous,andonlyaverysmall

areawasanalysed.

Moreover,amapwasmadeoftheelementspresentthroughoutthescanofthePGsamplethusallowinga

moreaccurateidentificationofthenatureofeachparticleintheselectedarea(Table5.8).

44

Figure5.7–SEMmicrographofP.SPsample(1500x),withtheeightstudiedparticles.

Table5.8–Atomicpercentageoftheelementsconstitutingeachparticle(P.SPsample,particlenumbersarethosefrom

Figure5.7)andmaininferredchemicalcompounds.

Particle 1 2 3 4 5 6 7 8

C 4.75 34.08 31.21 28.30

O 67.97 49.00 54.50 56.76 69.06 71.35 67.08 62.80

Mg 1.98 0.70

Al 21.97 8.79 7.07 6.38 1.38 2.74 1.71 3.57

Si 0.54 0.92 2.30 3.06

P 0.78 0.66 1.07 1.30 2.97 2.40 12.12

Ca 0.42 0.64 1.09 2.24 1.93 0.76 19.08 0.74

V 0.93

Mn 0.68 0.62

Fe 0.22 0.35 29.83

Y 4.96 3.29 2.12 23.98 21.20

Ba 0.76 0.23

La 0.29

Ce 1.07 0.12

Eu 0.41 0.10 0.13

Tb 0.53

Inferred

chemical

composition

CAT

Alumina

YOX

BAM

YOX

LAPorCa

halophosphate

YOX

Ca

halophosphate

YOX YOXCa

halophosphate

Fe

Alumina

SiO2

45

TheresultspresentinTable5.8leadtotheinferenceofcertainphasesforeachparticle,whencomparedto

theliterature.Halfoftheparticleshavecarbonwithin,whichisanon-expectedresult,sinceitwasnotusedto

prepareorhold the sample. It canbeattributed toorganic substancesadded in thebathof themechanical

processingusedbythecompany.Infact,thepulphadastrongodour,butnoinformationwasobtainedabout

thecompositionofthesolution,forconfidentialityreasons.Oxygenatomiccontentisalsohighwhencompared

withthemetalscontent,aswasdeterminedfromstoichiometriccalculationsbasedontheexpectedquantities

ofeachphosphorphase.However,theidentificationofthemainphaseswassuccessfullyachieved,aspresented

inthenextparagraphs.

Onparticle1,theexistenceofMg,Ce,TbandespeciallyAlandOinhighquantitiessuggeststhattheparticle

ismadeofCATorceriummagnesiumaluminate,terbiumdoped.Someamountofceriumphosphate(LAP-Ce

type)isalsoprobable.Thepresenceofsilicon,eventhoughbeingsmall,liketheliteraturesuggested,mustbean

impurityfromtheglassand/orbarrierlayeri.e.silica.PandCaarealsoexistent,whatcouldindicatethatthere

ispartofcalciumhalophosphatephosphor,asanimpurityaswell.Alispracticallyexplainedbytheatomicratio

betweenMg/AlinCATformula,andso,someeventualaluminapresentisvestigial.

InthesecondparticleanalysedthereisevidenceofthepresenceofYOX.BAMisalsopresentintheparticle

duetothe,practically,equalpercentageofBaandMg.ThepresentaluminiumismainlyfromtheBAMphosphor,

leavingresidualaluminaintheparticle.ThepresenceofEuisjustifiedbyitsuseasdopantinbothYOXandBAM

phosphors.SincethereisalsoPandCa,anequaldeductionismade,asintheparticle1case.

Thethirdandfourthparticleshaveresidualsilicapresentalso.BothseemtobemainlyconstitutedbyYOX

phosphor.EuisalsoidentifiedasYOXdopant.TheamountsofLa,CaandPinthethirdparticlealsoindicatethe

presenceofLAPandcalciumhalophosphate.InthefourththerelationbetweenpercentagesofCaandPsuggests

thereiscalciumhalophosphate,butalsosomeCephosphate.BothparticleshavealsoAlcontentsthatmustbe

attributedtoalumina.

ThefifthandsixthparticlesareYOXphosphortogetherwithsmalltracesofaluminaandhalophosphorparts;

MnandVareconsideredimpurities.Particle7compositionsuggeststhatitismadeofcalciumhalophosphate

sinceitismainlyconstitutedbyP,CaandO.

Finally,thelastparticleanalysedisconstitutedbyoxides,namelyironoxide,aluminaandsilica.Ironisalso

probablyacontaminantfromthelampofthetreatmentprocess.

ThemappingofthePGsampleresultedintheidentificationofthephasesillustratedinFigure5.8.Onemust

notethattheparticleswereidentifiedbythemajorcomponent.Duetothecrushing,thereareelementsspread

overthesample.

46

Figure5.8–SEMmicrographofPGsample(1500x).Particlesare:p–Calciumhalophosphate;u–YOX;À–BAM;l

–CAT;n–strontiumhalophosphate;Â–particlerichinFe.

5.2.4. ElementalanalysisbyICP-AESofinitialsamples

AsmentionedanICP-AESchemicalanalysiswasmadetosamplestreatedwithaquaregia,namedAR1and

AR2.Thepurposeistodeterminethetotalcontentofrare-earthsandothermetalsinthephosphorsampleas

wellastoevaluatethesolublepartofthosemetalsintheliquid.

Table5.9–Elementalcompositionofseveralmetalsinwastefractions(wt.%).AM–arithmeticmean;SD–standarddeviation.

Sample Al Ba Ca Ce Eu Gd Hg La Mg P Sr Tb Y MetalContent

REEcontent

AR.1 1.38 1.040 13.1 0.690 0.840 0.320 0.040 0.890 0.220 6.49 0.630 0.280 15.5 34.93 18.52

AR.2 1.27 1.050 12.9 0.480 0.840 0.320 0.038 0.540 0.210 6.28 0.620 0.210 14.6 33.08 16.99

AM 1.32 1.045 13.0 0.585 0.840 0.320 0.039 0.715 0.215 6.39 0.625 0.245 15.1 34.00 17.76

SD 0.08 0.007 0.14 0.148 0.000 0.000 0.001 0.247 0.007 0.15 0.007 0.049 0.64 1.31 1.08

Table5.9showsthattheREEcontentis17.76%drywt.(bysummingalltheREEs)inaverage,whichindicates

thatthefractionshaveinterestregardingurbanmining.

ThemainmetalimpuritieswerestudiedaccordingtopreliminarySEM/EDSresults.Calciumcontentisthe

mostpresent,followedbyaluminium,barium,strontium,magnesiumandmercury.

ThechemicalanalysisagreeswiththeresultsobtainedbyXRPDanalysisandSEMmicroscopy,thatthereis

mainlyYOXandcalciumhalophosphate inthewaste,asexpected;yttriumoxidecomprising15%ofthetotal

sample.SmallpercentagesofCBT,CAT,BAMandLAParepresent.

47

5.3. Leachingofphosphormaterials

5.3.1. LeachingwithHClsolutions

Thefirstseriesofleachingexperimentsaimedtotestseveralconditions(temperature,concentration,time)

usingHClasleachant,inordertoevaluatetheleachingyieldsofthemainelementssuchasLa,Ce,Eu,Gd,Tb,Y,

Ca,Al,asstatedinFlowchart4.3.InTable5.10arepresenttheleachingyieldsobtainedfromICPanalysisofthe

leachates,fortheexperimentsoneandtwo.

Table5.10–LeachingyieldsofREEsafterleachinginHClaccordingtoconditionsinTable4.2.Resultsin%.

Experiment Al Ca Ce Eu Gd La Tb Y

Experimentswithoutcalcination

0.5MHCl,90°C,1h 16.80 42.30 0.90 5.60 1.90 0.50 0.50 6.00

0.5MHCl,90°C,6h 2.30 44.70 2.30 24.80 6.90 0.60 1.70 22.80

4MHCl,90°C,1h 64.80 91.00 12.60 27.90 57.10 1.70 19.50 74.40

4MHCl,90°C,6h 95.30 102.30 19.30 27.90 88.70 2.20 28.90 85.10

0.5MHCl,25°C,1h 12.30 39.20 0.50 4.00 0.90 0.60 0.70 3.70

0.5MHCl,25°C,6h 16.50 40.80 0.70 11.30 1.90 0.80 1.20 10.00

4MHCl,25°C,1h 16.70 94.80 0.90 16.20 2.90 1.00 1.80 14.00

4MHCl,25°C,6h 23.60 99.60 1.90 27.90 7.60 1.30 3.40 67.10

Experimentswithcalcination

4MHCl,90°C,1h 68.70 95.40 15.30 27.90 72.80 1.70 22.80 78.30

4MHCl,90°C,6h 95.60 94.50 19.70 27.90 85.60 2.40 27.80 82.00

Inanoverallviewoftheresults,testscarriedoutathighervaluesoftemperatureandacidconcentration

weretheoneswherehighyieldsarose.Someelementswerealsoefficientlyleachedwhenusingthehigheracid

concentration, suchasCaandY.Therefore,onecanstate that theHCl leachingprocess resulted inselective

leachingofsomeREEs.ThechemicalprocessforleachingofREMsfromtheircorrespondingphosphorsusingan

acidicsolutioncanbewrittenasthefollowingsimplifiedequations,consideringthatvirtuallyallthemetalscould

bedissolved(whichdoesnotalwaysoccur):

1. Redphosphor:𝑌,𝑂8: 𝐸𝑢8< + 6𝐻< ↔ 2𝑌8<(+𝐸𝑢8<) + 3𝐻,𝑂;

2. Greenphosphors:𝐿𝑎𝑃𝑂@: 𝐶𝑒8<, 𝑇𝑏8< + 3𝐻< ↔ 𝐿𝑎8<(+𝐶𝑒8<, 𝑇𝑏8<) + 𝐻8𝑃𝑂@;

𝐺𝑑,𝑀𝑔 𝐵J𝑂4K: 𝐶𝑒8<, 𝑇𝑏8< + 18/17𝐻< ↔ 𝐺𝑑8<,𝑀𝑔,<(+𝐶𝑒8<, 𝑇𝑏8<) + 5/2𝐵,𝑂8 + 10𝐻,𝑂;

𝐶𝑒, 𝑇𝑏 𝑀𝑔𝐴𝑙44𝑂4N + 38𝐻< ↔ 𝐶𝑒8<, 𝑇𝑏8< + 𝑀𝑔,< + 11𝐴𝑙8< + 19𝐻,𝑂;

3. Bluephosphors:𝐵𝑎𝑀𝑔𝐴𝑙4K𝑂4O: 𝐸𝑢,< + 34𝐻< ↔ 𝐵𝑎,< + 𝑀𝑔,<(+𝐸𝑢8<) + 10𝐴𝑙8< + 17𝐻,𝑂;

𝑆𝑟, 𝐶𝑎, 𝐵𝑎,𝑀𝑔 J 𝑃𝑂@ 8𝐶𝑙: 𝐸𝑢,< + 10𝐻< ↔ 5 𝑆𝑟,<, 𝐶𝑎,<, 𝐵𝑎,<,𝑀𝑔,< +𝐸𝑢,< + 3 𝐻8𝑃𝑂@ + 𝐻𝐶𝑙.

48

Consumptionofprotonsoccursmakingacidconcentrationanimportantparameterintheleachingprocess.

Itwasindeednotedthathigheracidconcentration,i.e.higherprotonconcentrationresultedinmorequantity

ofleachedmetal.ThisparameterhoweverbarelyinfluencedLaleachingbehaviour.

Hydrochloricacidrevealedtobeaneffectiveleachantforaluminium,calcium,gadoliniumandyttrium.It

wasexpectedthateuropiumfollowedthetendency,howeveritssolidcontentwasonlyapprox.28%(with4M

at90°C).

Temperature increase influenced, significantly the leaching of Y, Al, Ce, Gd and Tb (Table 5.10). Higher

quantitiesofmetalsarecomingintothesolutionbyincreasingtemperaturefrom25°Cto90°C.Thetreatment

bycalcinationaffectedslightlytheleachingbehaviourofAl,Ce,Gd,La,TbandY.

ThemassbalancethroughouttheexperimentsispresentinTable5.11.

Table5.11–MassbalanceandvolumeofsolutionusedinexperimentsE1andE2.Samplesbythesameorderas.Table5.10.

Exp.1stLeaching 2ndStep(Calcination,Digestion) 2ndLeaching Massloss

m(g) Vtotal(mL) mf(g) m(g) Vacid(mL) mf(g) m(g) Vtotal(mL) mf(g) (%)

E1

0.590°C 5 50 3.98 20.4

0.525°C 5 50 1.88 24.4

4M90°C 5 50 3.78 62.4

4M25°C 5 50 2.12 57.6

E2 6 5.91 5.91 60 1.86 69.0

5.3.2. Evaluationofseveralacidleachatesandmultistepleaching

Since the leaching behaviour of the several REEs, contained in different phosphormaterials, was quite

diverse, several optional processes were proposed and tested, involving in some cases multistep leaching

operations and other complementary treatments. The aim was essentially to evaluate the possibility of

recoveringdifferentelementsindifferentsteps,thusimprovingtheselectivityofthetreatmentandsimplifying

thesubsequentseparationandrecoveryoperations.

Accordingwiththepreviousstatement,severaltreatmentoptionswereproposedforcomparisonandtested

experimentally:

• SingleleachingwithHCl(alreadytestedinprevioussection)–allowsefficientrecoveryofYandGd,but

notforLa,Ce,Tb,Eu;

• Two-stepleaching,bothwithHCl,withacalcinationoperation(atlowtemperature)includedbetween

thetwoleachingsteps(Exp.3)–tryingtoimprovetherecoveryofalltherare-earthsinthesecondstep

throughathermalactivationoftherespectivebearingphases;

• Two-stepleaching,thefirstwithHClandthesecondwithHNO3.(Exp.4)–tryingtoimprovetherecovery

ofalltherare-earthsbyadifferentleachingagent;

• Two-stepreaction,thefirstconsistingonHClleachingandthesecondbeingadigestionwithH2SO4(Exp.

5)–alsotryingtoimprovetherecoveryofalltherare-earthsbyadifferentacidagentandapproach

(digestioninsteadofleaching);

49

• SingleH2SO4 digestion (Exp. 6) – alternative chemical treatmentwith another acid rather thanHCl;

allowscomparisonwiththesingleHClleaching;

ThemassbalancethroughouttheexperimentsispresentinTable5.12.

Onemustnotethat,theseexperimentsaremulti-stepthushavingseveralsuccessivereactionsstepsand

alongwithitbothglobalandindividualefficiencyvalues.

Table5.12–MassbalanceandvolumeofsolutionusedineachexperimentE3-E6.

Exp.1stLeaching 2ndStep(Calcination,Digestion) 2ndLeaching Massloss

m(g) Vtotal(mL) mf(g) m(g) Vacid(mL) mf(g) m(g) Vtotal(mL) mf(g) (%)

E3 6 50 2.32 2.32 2.22 2.22 22 2,06 58.8

E4 6 50 2.36 2.36 25 2,03 66.17

E5 6 50 2.31 2.31 2.54 2.06 2.06 23 1,46 75.7

E6 5 5.5 4.32 4.32 50 2,77 53.8

Whentheefficiencycalculationswerebeingmade,itwasnoticeablethatintheprocessesinvolvingH2SO4,

moremetalswereobtainedinsolution,thanthepredictedinitially(forLa,CeandTb).Whatsuggeststhatthe

aqua-regiaattacks,inwhichtheinitialcompositionofthepowderwasdefined,maynothavebeencompleted.

Therefore,theinitialvalues(Table5.9)werecorrectedaccordingtothetotaldissolved.

TheleachingefficiencyisgivenbothinTable5.13andTable5.14,thefirstonepresentsrecoveryvaluesfor

theindividualsteps,whereasthesecondpresentstheaccumulatedvaluesattheendofeachexperiment.The

recovery percentage is also shown in the set of graphs below (Graph 5.1). However, unlike Table 5.13, the

percentages presented in the graphs are the percentages referring to the initial metal content, and not

percentagesofrecoveryofthematerialleftinthesolidbythepreviousstep.

Table5.13–OverviewoftheleachingbehaviourofREEs(valuesofextractionpercentageforeachstep,notaccumulated).

Elements

Recoveryefficiencyperprocedure

1stacidleaching

(E2,E3,E4andE5)

2ndStep+2ndleaching

E3 E4 E5 E6

REEs

Ce 10.20 56.09 81.85 93.68 99.18

Eu 27.93 0,00 0.00 1.58 67.67

Gd 88.69 0,00 0.00 0,00 94.60

La 1.11 58.42 89.42 94.71 99.86

Tb 14.18 58.36 84.30 96.93 99.40

Y 85.10 3.39 2.54 8.46 73.31

OthermetalsAl 70.38 7.70 8.70 95.62 85.22

Ca 98.54 15.28 15.38 15.19 8.71

50

Table5.14–Overallleachingyieldsattainedaftereachtreatmentprocess(6hofresidencetime).

ElementsLeachingyields(%)(accumulated,forallsteps)

E2 E3 E4 E5 E6

REEs

Ce 10.20 60.60 80.50 94.80 99.18

Eu 27.93 27.90 27.90 29.10 67.67

Gd 88.69 88.70 88.70 88.70 94.60

La 1.11 58.90 85.70 94.80 99.86

Tb 14.18 64.30 83.40 97.40 99.40

Y 85.10 85.60 85.40 86.30 73.31

OthermetalsAl 70.38 72.70 72.80 98.70 85.22

Ca 98.54 98.80 98.80 98.80 8.71

Asstatedbefore,thesinglestepleachingonlyallowsa,ratherhigh,Y,Al,CaandGdrecoveryhencethe

developmentofnewexperimentalprocedures.InexperimentE3,thecalcinationandsecondHClleachingmust

have,infact,thermallyactivatedthebearingphases,sinceitresultedintheincreaseofleachedLaandTbto

approx.58%andapprox.56%ofCe(Table5.13).EventhoughE3allowedandoverall recuperationofall the

identifiedmetals,mainlyGd,Y,CaandAl,values,apartfromCaandY,werethelowest(Table5.14).

InE4andE5,the2ndstepplus2ndleachingincreasedseverelytheCe,LaandTbextraction.E5alsoresulted

into further Al extraction (Table 5.13) eventually leading to the highest values for Al leaching (Table 5.14).

However,AlinsolutionwouldbeacontaminantforsubsequentREEsseparation.

ThevaluesforCarecoveryarehandtohandthroughouttheexperimentsapartfromthelastone.Itcanalso

bedenotedthatfromexperimentthreeuptofive,thereis[practically]noEuandGdandfewY.Thefactthata

“0.00”appearsdoesnotmeanthattherewerenoelementstoanalyseinsolutionbutonlythattheywerepresent

inaquantitylowerthanthedetectionlimitoftheequipment.(estimatedas<50ppb).

InE6thevaluesaremuchhigher(Table5.13),thisexperimenthasthehighestextractionefficiencyforCe,

Eu,Gd,LaandTb,butthelowestforCaandY.Theseresultssuggestthatthedigestionwithsulphuricacidseems

to be the most efficient process; it seems that metals reactivity with sulphuric acid is higher than with

hydrochloricornitricacid.ThecalciumleachingefficiencyattainedinE6,clearlylowerthantheobtainedinthe

otherexperiments,isrelatedtothelowersolubilityofthiselementinsulphatemedia(theoreticalsolubilityof

calciumsulphateisabout0.54-0.90gL-1,dependingonthetypeofcalciumsulphateformed).

Whencomparingvaluesfromtheliteraturetothefinalresultsobtained(Table5.15),onecannoticefirstly,

thatinthepublishedworkGd,LaandTbextractionwasnottestedor,regardlesstheexperimentalprocedure

chosen the valueswere too low;on theotherhand someexperimental protocols focusedonlyonEuandY

recoveryfromtheYOXphosphorwhichwasattainedatdifferentlevels,dependingontheleachingconditions.

51

Table5.15–ComparisonofREEsrecoverybetweenliteraturedataandpresentwork.“–”meanstheelementwasnotstudied.

Comparingelementbyelement,eventhoughsimilartechniqueswereused,theYOX’sREEs(EuandY),the

recoveryinthepresentworkwasnotsogoodsince,themajorityofthepublisheddataisover90%.E6wasmade

toallowcomparisontoasingleHClleaching,howevertheCeandTbobtainedvalueswerequitecomparable12

totheliterature’sandpresentworkdoubleHClleaching.Valuesfromexperimentsfourandfivewerebetterthan

the values found in the remaining bibliography. Furthermore,most of the published results are referred to

phosphors materials taken from lamps and not from the waste sludge fractions from treatment plants,

consequently,don’thaveasmanyimpuritiesassludge.

Comparingtheoverallresults,onepositiveoutcomeisthatallREEsinthefluorescentlampswereabletobe

leachedinexperimentsonetosix.Terbium,lanthanumandgadolinium,asmentioned,werenotstudiedin[most

of]theavailablepublishedbibliography,howeverhighpercentageswereobtained,especiallyinE5andE6.

12From95%thevaluesareallverysimilar,sincetheexperimentalerrorsofthistypeoftestscanbe3-5%.

Material Experiment

Leachingefficiency(%)

ReferenceEu Y La Ce Tb Gd

Fluo

res

cent

lamp

waste

fractio

ns 25%v/vCH3COOH 50 75 2-10 – –

[45]0,5M,1M,2M,4MHCl0,5M,1M,2M,4MHNO3

>95 >97 – – – –

Phosph

orsfromEOL

fluorescentlamps DoubleHCLleaching(3M,then5M) 97.38 99.06 98.22 98.15 – [42]

HNO3+H2SO4(4Meach) 92.8 96.4 – – – – [46]

2MH2SO4 71.5 75.3 – 61.1 66.9 – [47]2MH2SO4 – 90 – – – – [48]

5MHNO3+H2SO4+HCl >85 >91 – – – – [49]4MHCl – 96.28 – – – – [50]

Fluo

rescen

tlampwaste

fractio

ns

Presentwork

E3 27.90 85.60 58.90 60.60 64.30 88.70

E4 27.90 85.40 85.70 80.50 83.40 88.70

E5 29.10 86.30 94.80 94.80 97.80 88.70

E6 67.67 73.31 99.86 99.18 99.40 94.60

52

Graph5.1–Leachingyields,fortheseveralmetals,ineachtreatmentprocess,specifyingthecontributionofeachstep¢-1st

acidleaching;¢-2ndStep+2ndleaching.Theresultsonthebottomrefertothe1stacidleachingwhereastheonesontop

refertothe2ndStep+2ndleaching.

10.20 10.2 10.2 10.2 00

50.37

70.33

84.1299.2

0

20

40

60

80

100

E2 E3 E4 E5 E6

Cerecovery(%)

27.93 27.9 27.9 27.9 0

0 0.00 0.00 1.14

67.7

0

20

40

60

80

100

E2 E3 E4 E5 E6

Eurecovery(%)

88.69 88.7 88.7 88.7 0

0 0.00 0.00 0.0094.6

0

20

40

60

80

100

E2 E3 E4 E5 E6

Gdrecovery(%)

1.11 1.1 1.1 1.1 0.00

57.77

84.62

93.6699.9

0

20

40

60

80

100

E2 E3 E4 E5 E6

Larecovery(%)

14.18 14.2 14.2 14.2 0

0

50.09

69.23

83.18 99.4

0

20

40

60

80

100

E2 E3 E4 E5 E6

Tbrecovery(%)

85.1 85.1 85.1 85.1 0

0 0.51 0.36 1.26

73.3

0

20

40

60

80

100

E2 E3 E4 E5 E6

Yrecovery(%)

70.38 70.4 70.4 70.4 0

0 2.28 2.46

28.32

85.2

0

20

40

60

80

100

E2 E3 E4 E5 E6

Alleached(%)

98.54 98.5 98.5 98.5 0

0 0.22 0.21 0.22

8.7

0

20

40

60

80

100

E2 E3 E4 E5 E6

Caleached(%)

53

Chapter6. ConclusionandFutureWorkEndoflifefluorescentlampsareavaluablesourceofthreeoutofthefivemostcriticalrare-earthelements

i.e.europium,terbiumandyttrium;alsocontainingcerium,gadoliniumandlanthanum.

Therecoveryofrare-earthelementsfromlampphosphors’,unlikeotherrecyclingapproaches,leadstovery

pureendproducts.

In thiswork,multi-step leachingandseveralacid leachantswereevaluated inorder to recover theREEs

present if real fluorescent lamp waste fractions. Thematerial contained large amounts of impurities, most

notablyglass,butalsometallicandplasticpartsanddirtduetotherecyclingprocess.

Cerium, europium, gadolinium, lanthanum, terbium, and yttrium were the RE elements

identified,comprisingapprox.18%(drywt.)ofthesample,beingyttriumclearlypredominantwithabout15%.

Hydrochloricacidrevealeditselftobeaneffectiveleachantforaluminium,calciumbutalsoforgadolinium

andyttrium.Itwasexpectedthateuropiumfollowedthetendency,howeveritssolidcontentwasonlyapprox.

28%(with4Mat90°C).

Temperature increase influenced, significantly the leaching of yttrium, cerium, gadolinium and terbium.

Higherquantitiesofmetalsarebeingbroughtintothesolutionbyincreasingthetemperaturefrom25°Cto90°C.

Accordingtotheresults,onecanchoosetheprocedureaccordingtotheprioritizedelements.

Iftheleachingofyttriumisthemainfocus,thenthebestleachingconditionsare;leachingwithhydrochloric

acid(4M)for6hat90°C(85.10%ofYleached),orasulphuricaciddigestionfor3hat150°Cwithawaterleaching

(1M)for6hat40°C(73.31%ofYleached).

IfbothREEs inYOX’sphosphorsarethepriority,thenasulphuricdigestionprocess(1.1mLg-1,3h,150°C)

togetherwithwaterleachingisthebestsolution.However,thusincreasingtheeuropiumleachingyield(from

27.93%to67.67%)itreducestheyttrium’sto73.31%.Furthermore,thisprocessalsoledtoaleachingyieldof

over99%forlanthanum,ceriumandterbium,andaround95%ofgadolinium.

The digestion step (present in experiments five and six) resulted in the best results attained in this

work,consequently,itsuggeststhattheREMsinphosphorsaremorereactivewhenusingsulphuricacidthan

withhydrochloricornitricacids.Thisworkalsodemonstratedthepossibilityofatwo-stepleachingapproachto

allowselectivereactionofdifferentrare-earths,namelyYandGdinafirstHClleachingstep,andtheremaining

REEs(La,Ce,Tb,Eu)inasecondstepusingsulphuricaciddigestion.

Unlikemoststudiesperformed,whereYOXisthemainfocus,terbium,lanthanumandgadoliniumleaching

wasnotassuccessfulornotstudied,thepresentworkresulted inthe leachingofallsix identifiedrareearth

elements.

Futureworkconcernsadeeperanalysisofrare-earthsrecoveryandrecycling.

Methods to separate lamp fractions into individual lamp components need further improvements: the

resultant sludge contains a large amount of impurities, hence causing the need for a continuous/repetitive

sievingthroughouttheexperimentalwork.TofurtherimproveREErecyclingrate,logisticsinthebringingtheRE

scraps,shouldbeimproved.

54

Whenthesamplesweredried,toplayerandsuprasampleswereproduced,sincethesurfacebecameway

darkerthantheremainingsample.However,noanalysiswasdonetothesesamples.Thesamehappenstothe

supernatantliquid.Itshouldbeinterestingtofigureoutwhatthecompositioninbothcasesis.

It couldbe interesting to furtherexplore thedigestionprocedure insteadof leachingprocesses,asmost

literaturespoint.

ExtractionoftheretrievedREEswasnotperformed,asmentioned,sinceitgoesoutoftheworkcontext:this

thesis focused both in characterization and recovery via physical-chemical processes. Therefore, extraction

mechanismsshouldbetested.

55

Bibliography[1] P.Henderson,J.Gluyas,GusGunn,F.Wall,AlanWoolley,andA.Finlay,“RareEarthElementsBriefing

Note.”TheGeologicalSocietyofLondon,pp.1–13,2011.

[2] K.Binnemansetal.,“Recyclingofrareearths:Acriticalreview,”J.Clean.Prod.,vol.51,pp.1–22,2013.

[3] A.W.Group,“CriticalrawmaterialsfortheEU,”ReportoftheAd-hocWorkingGroupondefiningcritical

rawmaterials,vol.39,no.July.pp.1–84,2010.

[4] J.M.Klinger,“Ahistoricalgeographyofrareearthelements:Fromdiscoverytotheatomicage,”Extr.

Ind.Soc.,vol.2,no.3,pp.572–580,2015.

[5] K.Binnemans, “EconomicsofRareEarths: theBalanceProblem,”1stEuropeanRareEarthResources

Conference.pp.37–46,2014.

[6] D. Girardi, “Market Dynamics,” Texas Mineral Resources, 2014. [Online]. Available:

http://tmrcorp.com/ree/market_dynamics/.[Accessed:12-Jan-2017].

[7] L. Erdmann and T. E. Graedel, “Criticality of non-fuel minerals: A review of major approaches and

analyses,”Environ.Sci.Technol.,vol.45,no.18,pp.7620–7630,2011.

[8] R.L.Moss,E.Tzimas,H.Kara,P.Willis,andJ.Kooroshy,“CriticalMetalsinStrategicEnergyTechnologies,”

2011.

[9] MIT,“Rare-EarthelementsSupplyandDemand,”TheFutureofStrategicNaturalResources:TheProblem,

2017. [Online]. Available: http://web.mit.edu/12.000/www/m2016/finalwebsite/problems/ree.html.

[Accessed:25-Feb-2017].

[10] S.Chu,“CriticalMaterialsStrategy,”U.S.DepartmentofEnergy.U.S.DepartmentofEnergy,p.191,2011.

[11] A.W.Group,“AnnexV,”ReportoftheAd-hocWorkingGroupondefiningcriticalrawmaterials,vol.39.

EuropeanCommission:EnterpriseandIndustry,pp.160–161,2010.

[12] E.Alonsoetal.,“EvaluatingRareEarthElementavailability :aCaseWithRevolutionaryDemandFrom

CleanTechnologies,”Environ.Sci.Technol.,vol.46,pp.3406–3414,2012.

[13] R.Kefferpütz,“UnearthingChina’sRareEarthsStrategy,”CEPSPolicyBrief,no.218.CenterforEuropean

PolicyStudies,pp.1–5,2010.

[14] J.Gambogi,“GlobalRareEarthOxide(REO)ProductionTrends,”U.S.GeologicalSurvey,2012.[Online].

Available: http://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/ree-trends-2010.pdf.

[Accessed:17-Jul-2016].

[15] K.Binnemans,P.T.Jones,K.VanAcker,B.Blanpain,B.Mishra,andD.Apelian,“Rare-eartheconomics:

Thebalanceproblem,”Jom,vol.65,no.7,pp.846–848,2013.

[16] C.Remeur,“Rareearthelementsandrecyclingpossibilities.”LibraryoftheEuropeanParliament,pp.1–

6,2013.

[17] R. HandBook, “Introduction,” 2013. [Online]. Available: http://www.reehandbook.com/intro.html.

[Accessed:02-Jan-2012].

[18] V.B.Grasso,“RareEarthElementsinNationalDefense:Background,OversightIssues,andOptionsfor

Congress,”ReportforCongress.CongressionalResearchService(CRS),p.43,2011.

[19] Anzaplan, “Rare Earth Minerals,” Rare Earth Minerals Processing, 2016. [Online]. Available:

56

http://www.anzaplan.com/strategic-minerals-metals/rare-earth-minerals/.[Accessed:12-Jan-2017].

[20] E. Springs et al., “Major Mineral Ores,” 2014. [Online]. Available:

http://robertbeauford.net/rare_earth_elements/ree_ores.

[21] ANZAPLAN, “Rare Earth Mineral Resources,” 2016. [Online]. Available:

http://www.anzaplan.com/strategic-minerals-metals/rare-earth-minerals/rare-earth-mineral-

resources/.[Accessed:12-Jan-2017].

[22] A.WaltersandP. Lusty, “Definitions,mineralogyanddeposits,”Rareearthelements,no.November.

BritishGeologicalSurvey-NaturalEnvironmentResearchCouncil,p.54,2011.

[23] LuísPlácidoMartins,“MineralResourcesofPortugal.”DirecçãoGeraldaEnergiaeGeologia,p.54,2013.

[24] A.Filipeetal.,“RecursosMinerais:OPotencialdePortugal,”Estratégia Nacional para os Recursos

Geológicos e Recursos Minerais.LaboratórioNacionaldeEnergiaeGeologia(LNEG),p.37,2010.

[25] Á.Oliveira,P.A.Dinis,R.Santos,andF.Rocha,“RAREEARTHELEMENTSINTHEPLIOCENESEDIMENTS

BETWEENRIVERSVOUGAANDMONDEGO(PORTUGAL).”VIIICongressoIbéricodeGeoquímica-XVII

SemanadeGeoquímica,pp.1–5,2011.

[26] D.G.RichardsonandT.C.Birkett,“RareMetals.Rawmaterialsfortechnologiesofthefuture,”vol.540,

no.8.SwissAcademyofEngineeringSciences(SATW),pp.523–540,2010.

[27] C.Bontron,“EnChine,lesterresrarestuentdesvillages,”LeMonde,no.Environment,p.3,2012.

[28] K.G.Thomas,“Rare-EarthElements(REEs)uses,demand&supply,”no.December.CanandianInstitute

ofMining,MetallurgyandPetroleum(CIM),pp.1–28,2014.

[29] X. J.Yang,A.Lin,X.L.Li,Y.Wu,W.Zhou,andZ.Chen, “China’s ion-adsorptionrareearthresources,

miningconsequencesandpreservation,”Environ.Dev.,vol.8,no.1,pp.131–136,2013.

[30] X.Li,Z.Chen,Z.Chen,andY.Zhang,“Ahumanhealthriskassessmentofrareearthelementsinsoiland

vegetables fromaminingarea inFujianProvince,SoutheastChina,”Chemosphere,vol.93,no.6,pp.

1240–1246,2013.

[31] G.Pagano,M.Guida,F.Tommasi,andR.Oral, “Healtheffectsandtoxicitymechanismsof rareearth

elements-Knowledgegapsandresearchprospects,”Ecotoxicol.Environ.Saf.,vol.115,pp.40–48,2015.

[32] K.T.Rim,K.H.Koo,andJ.S.Park,“Toxicologicalevaluationsofrareearthsandtheirhealthimpactsto

workers:aliteraturereview.,”Saf.HealthWork,vol.4,no.1,pp.12–26,2013.

[33] T.G.Goonan,“RareEarthElements—EndUseandRecyclability,”ScientificInvestigationsReport2011-

5094.U.S.GeologicalSurvey,pp.1–15,2011.

[34] S.Balesteiro,“Maispontosderecolhadelâmpadasvelhas,”SOL,p.3,2015.

[35] C.M.MartinsandP.A.dosS.Ferreira.,“Despachon.o4745/2016.”DiáriodaRepública,2.asérie—N.o

68,pp.11602–11603.

[36] J. de Extremadura, “Recicla la Luz.” [Online]. Available:

http://www.merida.es/descargas/medioambiente/compendio/articulos/recicla-la-luz.pdf. [Accessed:

01-Jun-2017].

[37] GELFOR,“SereducelatasaECORAEEenalgunaslámparas,”2017.[Online].Available:http://gelfor.es/se-

reduce-la-tasa-ecoraee.[Accessed:06-Jun-2017].

57

[38] C.Tunsu,M.Petranikova,M.Gergori??,C.Ekberg,andT.Retegan,“Reclaimingrareearthelementsfrom

end-of-life products: A review of the perspectives for urban mining using hydrometallurgical unit

operations,”Hydrometallurgy,vol.156,pp.239–258,2015.

[39] C.Tunsu,M.Petranikova,C.Ekberg,andT.Retegan,“Ahydrometallurgicalprocessfortherecoveryof

rareearthelementsfromfluorescentlampwastefractions,”Sep.Purif.Technol.,vol.161,pp.172–186,

2016.

[40] K.BinnemansandP.T.Jones,“Perspectivesfortherecoveryofrareearthsfromend-of-lifefluorescent

lamps,”J.RareEarths,vol.32,no.3,pp.195–200,2014.

[41] M.K. Jha,A.Kumari,R.Panda, J.RajeshKumar,K.Yoo,and J.Y.Lee,“Reviewonhydrometallurgical

recoveryofrareearthmetals,”Hydrometallurgy,vol.165,pp.2–26,2016.

[42] S.-G.Zhang,M.Yang,H.Liu,D.-A.Pan,andJ.-J.Tian,“Recoveryofwasterareearthfluorescentpowders

bytwostepsacidleaching,”RareMet.,vol.32,no.6,pp.609–615,2013.

[43] R.OttoandA.WojtaleWicz-Kasprzak,“MethodForRecoveryOfRareEarthsFromFluorescentLamps,”

US2012/0027651A1,2012.

[44] K. Binnemans and D. Dupont, “Process for recovery of yttrium and europium from lamp phosphor

waste,”WO2016065433A1,2015.

[45] C.Tunsu,C.Ekberg,M.Gergoric,andT.Retegan,“Characterizationandleachingofrealfluorescentlamp

wastefortherecoveryorrareearthmetalsandmercury,”Hydrometallurgy,vol.144–145,pp.91–98,

2014.

[46] M. A. Rabah, “Recyclables recovery of europium and yttrium metals and some salts from spent

fluorescentlamps,”WasteManag.,vol.28,no.2,pp.318–325,2008.

[47] L. Hong-Mei, “Recovery of rare earth from waste rare earth phosphor powder by acid leaching,”

Hydrometallurgy,vol.29,pp.188–190,2010.

[48] I.DeMichelis,F.Ferella,E.F.Varelli,andF.Vegliò,“Treatmentofexhaustfluorescentlampstorecover

yttrium:Experimentalandprocessanalyses,”WasteManag.,vol.31,no.12,pp.2559–2568,Dec.2011.

[49] F.Yang,F.Kubota,Y.Baba,N.Kamiya,andM.Goto,“Selectiveextractionandrecoveryofrareearth

metals from phosphor powders inwaste fluorescent lamps using an ionic liquid system,” J. Hazard.

Mater.,vol.254–255,pp.79–88,Jun.2013.

[50] X.Wang,G.Mei,C.Zhao,andY.Lei,“RecoveryofRareEarthsfromSpentFluorescentLamps,”in5th

InternationalConferenceonBioinformaticsandBiomedicalEngineering,2011,pp.1–4.

[51] R.Shimizu,K.Sawada,Y.Enokida,andI.Yamamoto,“Supercriticalfluidextractionofrareearthelements

fromluminescentmaterialinwastefluorescentlamps,”J.Supercrit.Fluids,vol.33,no.3,pp.235–241,

2005.

59

AnnexI. RareEarthbearingmineralsTableI.1–Selectedrare-earthmineralsbearingeitherLREEand/orHREE.

SelectedMinerals LREE HREE

A

Aeschenite(Nd)-

(Nd,Ce,Ca)(Ti,Nb)2(O,OH)6Neodymium

Allanite(Ce)-

(Ca,Ce)(Al2,Fe+2)(Si2O7)(SiO4)O(OH)

Cerium,Praseodymium,Neodymium,

Samarium,Europium

Allanite(Y)-

(Ca,Ce)(Al2,Fe+2)(Si2O7)(SiO4)O(OH)

Terbium;Erbium

Ancylite(Ce)-SrCe(CO3)2(OH)•H2O Samarium,Europium,Gadolinium

Åskagenite(Nd)-

(Mn2+,Nd)(Al2,Fe3+)(Si2O7)(SiO4)O2

Neodymium

B

Bastnäsite(Ce,La,Nd,Pr)(CO3)F


Samarium,Europium,Gadolinium,

Lanthanium

Dysprosium

Bastnäsite(Nd)(Nd,Ce,La,Pr)(CO3)F Neodymium

Bazzite:Be3Sc2(Si6O18) Scandium

C

Cerite-(Ce)

(Ca,Ce)9(Fe,Mg)(SiO4)3(HSiO4)(OH)3Cerium,Praseodymium Terbium,Erbium

Clays:Y-enrichedlateric Europium

Ytrium,Terbium,Dysprosium,

Erbium,Thulium,Ytterbium,

Lutetium

Clays:Ionadsorptionlateric Europium

Ytrium,Terbium,Dysprosium,


Lutetium

E

Euxenite-(Y)(Y,Ca,Ce,U,Th)(Nb,Ti,Ta)2O6 Terbium,Erbium

Eudialyte-(Y)

Na4(Ca,Ce)2(Fe2+,Mn,Y)ZrSi8O22(OH,Cl)2

Yttrium,Terbium,Dysprosium,

Holmium,Erbium,Ytterbium,

Lutetium

F

Fergusonite-(Nd)(Nd,Ce)(Nb,Ti)O4 Neodymium

Florencite-(Nd)(Nd,La,Ce)Al3(PO4)2(OH)6 Neodymium

G

60

Gadolinite-(Y)Y2Fe2+Be2(Si2O10) Gadolinium

Terbium,Dysprosium,Holmium,


Lutetium,Yttrium

I

Iimoriite-(Y)Y2(SiO4)(CO3) Terbium,Erbium

Sc-Ixiolite:(Nb,Ta,Ti,Sc,Fe,Mn)4O8 Scandium

L

Lanthanite-(Nd)(Nd,La)2(CO3)3•8H2O Neodymium

Loparite-(Ce)

(Ce,Na,Ca,Sr,Th)(Ti,Nb,Ta,Fe+3)O3


Saramarium,Europium,GadoliniumErbium,Ytterbium

Loparite(Ce,Na,Sr,Ca)(Ti,Nb,Ta,Fe+3)O3 Lanthanum

M

Magbasite:KBa(Al,Sc)Fe2+Mg5F2Si6O20 Scandium

Monazite(Ce,La,Nd,Th)(PO4)Lanthanum,Neodymium,Samarium,

Europium,Gadolinium

Yttrium,Terbium,Erbium,

Ytterbium

Monazite-(Nd)(Nd,Ce,La,Th)(PO4) Neodymium Ytterbium

MosandriteNa2Ca4(REE)(Si2O7)2OF3 Terbium,Dysprosium,Erbium,

Thulium,Ytterbium,Lutetium.

P

Parisite-(Ce)Ca(Ce,La)2(CO3)3F2 Neodymium,Europium

Parisite-(Nd)Ca(Nd,Ce,La)2(CO3)3F2 Neodymium

Perrierite:(Ce,Ca,

Th)4(Fe2+,Sc)Fe2

3+(Ti,Fe3+)2(Si2O7)2O8 Scandium

R

Rhabdophane-(Nd)(Nd,Ce,La)(PO4)•H2O Neodymium

S

Samarakite-(Y)

(Y,Fe+3,Fe+3,U,Th,Ca)2(Nb,Ta)2O8Samarium,Gadolinium

Synchysite-(Nd)Ca(Nd,Y,Gd)(CO3)2F Neodymium

Synchysite-(Y)Ca(Y,Ce)(CO3)2F


Holmium,Erbium,Thulium,

Ytterbium,Lutetium

T

Thortveitite:(ScY)2Si2O7 Scandium

U

Uraninite Promethium

X

61

XenotimeY(PO4)


Holmium,Erbium,Thulium,

Ytterbium,Lutetium

TheorderisaccordingtoREEatomicnumber

63

AnnexII. Rare-earthToxicologicalInformationTableII.1–Summaryoftoxicologicalinformationwithrare-earths[32].

Z13

Symbol Name CASNo. ToxicologicalInformation14

21 Sc Scandium 7440-20-2

Elemental scandium is considerednon-toxic, and little animal testing of

scandiumcompoundshasbeendone.Thehalflethaldose(LD50)levelsfor

scandium (III) chloride for rats have been determined as 4mg/kg for

intraperitoneal,and755mg/kgfororaladministration.

39 Y Yttrium 7440-65-5

Watersolublecompoundsofyttriumareconsideredmildlytoxic,whileits

insoluble compounds are non-toxic. In experiments on animals, yttrium

and its compounds caused lung and liver damage. In rats, inhalation of

yttriumcitratecausedpulmonaryedemaanddyspnea,whileinhalationof

yttrium chloride caused liver edema, pleural effusions, and pulmonary

hyperemia. Exposure to yttrium compounds in humansmay cause lung

disease.

57 La Lanthanum 7439-91-0

Inanimals,theinjectionoflanthanumsolutionsproduceshyperglycaemia,

lowbloodpressure,degenerationof the spleenandhepaticalterations.

Lanthanum oxide (1312-81-8) LD50 in rat oral (> 8 500mg/kg), mouse

intraperitoneal(i.p.)(530mg/kg).

58 Ce Cerium 7440-45-1

Ceriumisastrongreducingagent,andignitesspontaneouslyinairat65°C

to 80°C. Fumes from cerium fires are toxic. Animals injectedwith large

dosesofceriumhavediedduetocardiovascularcollapse.Cerium(IV)oxide

is a powerful oxidizing agent at high temperatures, and will react with

combustible organic materials. Ceric oxide (1306-38-3) LD50 in rat oral

(5000mg/kg),dermal(1000-2000mg/kg),inhalationdust(5.05mg/L).

59 Pr Praseodymium 7440-10-0 Praseodymiumisoflowtomoderatetoxicity.

60 Nd Neodymium 7440-00-8

Neodymium compounds are of low to moderate toxicity; however, its

toxicityhasnotbeenthoroughlyinvestigated.Neodymiumdustandsalts

arevery irritating to theeyesandmucousmembranes, andmoderately

irritating to the skin. Neodymium oxide (1313-97-9) LD50 in rat oral (>

5000mg/kg), mouse i.p. (86mg/kg), and Nd2O3was investigated as a

mutagen.

61 Pm Promethium 7440-12-2

It is not known what human organs are affected by interaction with

promethium; apossible candidate is thebone tissue.Nodangers, aside

fromtheradioactivity,havebeenshown.

13Z:atomicnumber.14 Mostly referred from National Toxicology Program database search application

(http://tools.niehs.nih.gov/ntp_tox/index.cfm) and material safety data sheets information in KOSHANET(http://www.kosha.or.kr/bridge?menuId=69). Searches were conducted using keywords chemical name AND/OR CASnumber

64

62 Sm Samarium 7440-19-9

Thetotalamountofsamariuminadultsisabout50μg,mostlyinliverand

kidneys,andwithabout8μg/Lbeingdissolvedintheblood.Insolublesalts

of samarium are nontoxic, and the soluble ones are only slightly toxic.

Wheningested,onlyabout0.05%ofsamariumsaltsisabsorbedintothe

bloodstream,andtheremainderisexcreted.

Fromtheblood,about45%goestotheliver,and45%isdepositedonthe

surfaceofthebones,whereitremainsforabout10years;thebalanceof

10%isexcreted.

63 Eu Europium 7440-53-1

Therearenoclearindicationsthateuropiumisparticularlytoxiccompared

to other heavymetals. Europium chloride nitrate and oxide have been

testedfortoxicity:europiumchlorideshowsanacutei.p.LD50toxicityof

550mg/kg, and the acute oral LD50 toxicity is 5 000mg/kg. Europium

nitrateshowsaslightlyhigheri.p.LD50toxicityof320mg/kg,whiletheoral

toxicityisabove5000mg/kg.

64 Gd Gadolinium 7440-54-2

Asafreeion,gadoliniumishighlytoxic,butmagneticresonanceimaging

contrastagentsarechelatedcompounds,andareconsideredsafeenough

tobeusedinmostpersons.Thetoxicitydependsonthestrengthofthe

chelating agent. Anaphylactoid reactions are rare, occurring in

approximately0.03-0.1%.

65 Tb Terbium 7440-27-9Aswiththeotherlanthanides,terbiumcompoundsareoflowtomoderate

toxicity,althoughtheirtoxicityhasnotbeeninvestigatedindetail.

66 Dy Dysprosium 7429-91-6

Soluble dysprosium salts, such as dysprosium chloride and dysprosium

nitrate,aremildlytoxicwheningested.Theinsolublesalts,however,are

non-toxic. Based on the toxicity of dysprosium chloride to mice, it is

estimatedthattheingestionof500gormorecouldbefataltoahuman.

67 Ho Holmium 7440-60-0The element, aswith other RE, appears to have a low degree of acute

toxicity.

68 Er Erbium 7440-52-0Erbiumcompoundsareoflowtomoderatetoxicity,althoughtheirtoxicity

hasnotbeeninvestigatedindetail.

69 Tm Thulium 7440-30-4

Soluble thulium salts are regarded as slightly toxic if taken in large

amounts,buttheinsolublesaltsarenon-toxic.Thuliumisnottakenupby

plantrootstoanyextent,andthusdoesnotgetintothehumanfoodchain.

70 Yb Ytterbium 7440-64-4

Allcompoundsofytterbiumshouldbetreatedashighlytoxic,becauseitis

known to cause irritation to the skin and eye, and some might be

teratogenic.

71 Lu Lutetium 7439-94-3

Lutetium is regarded as having a low degree of toxicity: for example,

lutetiumfluorideinhalationisdangerousandthecompoundirritatesskin.

Lutetium oxide powder is toxic as well if inhaled or ingested. Soluble

lutetiumsaltsaremildlytoxic,butinsolubleonesarenot.

65

AnnexIII. MoistureContentCalculationsForthesupernatantpulpwithinitialmassof𝑚oq = 1052.6𝑔,afterdryingonehas:

𝑚al 𝑑𝑟𝑦y]\ = 1708.0 − 984.5𝑔 = 723.5𝑔,

were1708.0𝑔isthetotalmassand984.5𝑔themassoftheoriginalcontainer.

𝑚al 𝑑𝑟𝑦z]_{ = 𝐺4b = 775.0 − 217.2 = 557.8𝐺,b = 268.4 − 102.7 = 165.7 → = 723.5𝑔

Giventheformationofblocks,whenthemasswastransferredfortwogoblets,therewasnolossofmass.

Hencethedrycakemasswas723.5𝑔,whichresultsinamassloss:Δ𝑚 = 1052.6 − 723.5 = 329.1.

Sothelossofmassrepresentsapercentageofmoistureof:

%~]�o\pr� =329.1×1001052.6

≈ 31.27%

Forsample1:

𝑚4 𝑑𝑟𝑦y]\ = 1146.2𝑔

𝑚4 𝑑𝑟𝑦z]_{ =𝐺4.4 = 604.1𝐺4., = 539.8 → = 1143.9𝑔

Itisverifiedthatwhenthemassistransferredintothegobletstherewerelossesof2.3g.Giventheproximity

ofthevalues,andtakingintoaccount,comparativelyothersamples,wherethelossofmassfromhottocoldhas

beenpracticallynil,themassofdrycakewillbeconsidered1146.2𝑔.

SoΔ𝑚 = 542.5,andtherefore%~]�o\pr�o ≈ 32.1%.

Forsample12:

𝑚4, 𝑑𝑟𝑦y]\ = 1008.9𝑔

𝑚4, 𝑑𝑟𝑦z]_{ = 𝐺4,.4 = 470.5𝐺4,., = 537.5 → = 1008.0𝑔

As seen themass lossdue to the transferof recipients is smaller than1𝑔. Like theabovecases, for the

calculationofthemoisturecontentoneconsidersthatthemassofthedrycakeis:1008.9𝑔.

SoΔ𝑚 = 398.8,andtherefore%~]�o\pr�o ≈ 28.3%.

Forsample19,eventhoughitIsexpectedthepercentageofmoisturetodiminish,asnoted,partoftheafloat

liquidwasaddedatthispointowingtothehighconsistencyofthesludge.

𝑚4N 𝑑𝑟𝑦y]\ = 525.9𝑔

𝑚4N 𝑑𝑟𝑦z]_{ =𝐺4,.4 = 270.8𝐺4,., = 254.7 → = 525.5𝑔

Consideringthatthefinalmassis525.9𝑔,onehasΔ𝑚 = 215.8𝑔andtherefore%~]�o\pr�o ≈ 29.1%.

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