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Technological Feasibility Study on Recovery of Metals from One

Computer Center of the FCQI

M.C. Miguel Aguilar Cortes1([email protected]), Dra. Martha Domnguez Patio

2, M.I. Nadia Lara

Ruiz1, M.E.M. Luz Elva Marn Vaca

1, Dra. Rosa Mara Melgoza Aleman

2.

1

Doctorado en Materiales en el Centro de Investigacin en Ingeniera y Ciencias Aplicadas, UniversidadAutnoma del Estado de Morelos, Mxico, Av. Universidad 1001, Col. Chamilpa, Cuernavaca Morelos,

Mxico, CP 62209.2Facultad de Ciencias Qumicas e Ingeniera, Universidad Autnoma del Estado de Morelos, Av.

Universidad 1001, Col. Chamilpa, Cuernavaca Morelos, Mxico, CP 62209.

NTRODUCTION

The speed with which electronic devices are innovated and also disposed of the same

promptly brings as consequence that such devices become obsolete to producing a new

scrap: electronic waste or e-waste, which is identified as all that waste from electrical or

electronic equipment such as computers. This material not properly stored becomes

nature and pollutes it.

Thousands of new electronic devices that displace others that arise every day considered

to be obsolete are unconsciously discarded in the trash either accumulated without care

to prevent that continues polluting. 70% of toxins deriving from waste landfills come

from e-waste.

It is not only that they currently this type of waste represents only 1% of the total

volume of the landfills. Imagine the amount of pollutants and the damages that come off

if you follow rising the amount of electronic waste discarded unconsciously ininappropriate places.

The contamination of soil, groundwater from wells and in general the entire ecosystem

is the result of lack of knowledge on issues of environmental health preservation. What

seems is not to be alarmed if it is not if we take into account that in Mexico it is only

and 4% of all the toxic waste is reused and the rest goes straight to inadequate landfills

of waste and landfills, which brings as a consequence the increase in pollutants that they

are generated into the environment.

Continuously replacing our technological equipment, the amount of waste that is

generated, this not counting the environmental costs to produce them, the manufactureof conventional PC 240 kilograms of hydrocarbons and 22 kilograms of other chemicals

are needed. This tells us that the world production of tens of millions of computers per

year has a very high environmental cost. Add to these requirements by team 1.5 tons of

water, by which computer equipment can consume the equivalent to a vehicle weight

all-terrain before leaving the factory. If we take into account that on average every 2

years and a half teams are changed and it is estimated that each year an equivalent is

generated in waste to 50% of the annual production of new equipment, thus having

134.5 million PCs by obsolete as well as 348.9 million of other electronic. Across the

continent, the annual scrap is 583.8 million units with a growth between 16% and 28%

every five years.


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ICT are based on hydrometallurgical, pyrometallurgical (Long et al., 2010), (Zhou and

Qiu, 2010), processes (Havlik et al., 2011) and biometalurgicos (Liang et al., 2010),

(Chi and col., 2011), (Zhu and col., 2011).

The present paper develops a test of technical feasibility, raised by Yang at laboratory

scale, as a methodology for the recovery of metals from TCI. This proposal is made as afirst contribution to a full recycling process that allows taking advantage of the greater

amount of WEEE. The proposed methodology is based on physical and chemical

operations of processing of minerals, such as reduction in size and classification,

concentration by magnetic separation, leaching and purification of metals.

METHODOLOGY

The experimental development of the proposed methodology was processed 1000 g of

material formed by the CPU (mainboard) motherboards. These cards are made

practically of the same electronic devices (capacitors, resistors, transistors, integrated

circuits, etc.).

Full processing consisted of preparation, reduction of size and classification, magnetic

separation, leaching, separation and purification of metals (Figure 1).

TARJETAS DECIRCUITOS IMPRESOS

(TCI)

COMPOSICIN:Cu, Al, Pb, Zn, Fe, Ni, Sn,Au, Pt, Ag, CERAMICOS Y

PLASTICOS

PREPARACIN

REDUCCIN DELTAMAO Y

SEPARACIN

SEPARACINMAGNTICA

LIXIVIACIN(H2SO4, H2O2)

RESIDUOS

MAGNETICOS YNO

CONDUCTORES

SEPARACIN YPURIFICACIN

Figura 1. Diagrama de flujo del proceso experimental.

Samples were taken from each stream for chemical analysis, which were dissolved in

aqua regia. The analysis of metals was made by Atomic adsorption.

Metals are leached in dilute sulfuric acid solution. Hydrogen peroxide, as oxidizing

agent, because we used a found in metallic form.

The test was performed with 70 g of the concentrated material, using an aqueoussolution of 1.5 L with commercial H2SO4 to 50% in excess and to 100% in excess, to


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an operating temperature of 35 C and with a 620 rpm agitation. The test was made for

120 min and added an equivalent amount to 50% of the stoichiometric at 60 min after

the start of the test.

RESULTS

This test was made in a beaker of glass of two litres capacity on an IKA C-MAG HP 10

iron and with a Heidolph RZR 2102 stirrer control (for copper).

As a result of the process of magnetic separation concentrates two copper 63% are

obtained. Coarse-size were taken between 1.0 mm and 2.0 mm and a fraction of fine

< 0.5 mm.

Copper in the magnetic fraction losses are 17%. These are due to some pins are copper

coatings of nickel (Oliveros, 2011) and therefore respond to magnetic fields being then

thrown to the magnetic current.

The result of the leaching process is presented in Figure 2. After two hours of leaching

copper concentration 25 g/l equivalent to 87% of the total of the copper in the sample is

obtained. After 30 minutes the leaching of copper is 78%.

Figure 2. Copper VS concentration curve time of leaching.

You can see how 30 minutes converges the leaching of copper and from 60 minutes

again dissolution since added more hydrogen peroxide.

CONCLUSIONS

A concentration back and efficient recovery of valuable metals from electronic scrap is

required for a good release of the species of interest in the process of downsizing, where

it was found that the coarse fraction is the richest in copper, a result expected due to the

properties of this metal. In addition the physical processes of magnetic concentration

were shown to be efficient in the recycling process and represent an excellent

alternative since they do not generate pollution.

Selective dissolution stage allowed a rich in copper sulphate solution suitable for further

recovery of the same. In this way you can retrieve other valuable metals taking

advantage of e-waste as a secondary source of these.

0

10

20

30

0 50 100 150Concentrationo

fCu(

g/L)

Time (min.)

Concentration of Cu vs. time

of leaching


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Final obtaining of copper can be done by means of electrode position and this is a

technique that does not generate large wastewater since the solutions are recirculating to

the leaching process. The accomplished process showed that it is feasible to technically

obtain a copper without refining with a purity exceeding 99%, from computer printed

circuit boards.

Evident then is the applicability of mineral processing techniques to separate the metal

fractions, ceramics and polymers of ICT and recover copper metallurgical techniques,

as an alternative solution to the problem of final disposal of WEEE, and which is

friendly to the environment, thus contributing to global sustainable development.

BIBLIOGRAPHY

[1]Ballester A., Verdeja L.F., Sancho J., Metalurgia extractiva. Fundamentos,Volumen 1, Editorial Sntesis, S.A., Madrid, Espaa (2000).

[2]Blaser F., Diagnstico de Electrodomsticos y de Aparatos Electrnicos deConsumo. Swiss Federal Laboratories for Materials Testing and Research

(Empa), Asociacin Nacional de Empresarios de Colombia (ANDI). (2009),

Pg. 122.

[3]Cceres G., Hidrometalurgia y electrometalurgia. Universidad de Atacama,(2007), pg. 183.

[4]Chi T.D., Lee, J-C., Pandey B.D., Yoo K.K., Jeong, J., Bioleaching of gold andcopper from waste mobile phone PCBs by using a cyanogenic bacterium.

Minerals Engineering. 24, 1219-1222 (2011).

[5]Cui, J.R., Zhang, L.F., Metallurgical recovery of metals from electronic waste:Areview, Journal of Hazardous Materials, 158, 228-256 (2008).

[6]Harue Yamane, L., Tavares de Moraes V., Romano Espinosa D.C.,SoaresTenrio J.A., Recycling of WEEE: Characterization of spent printed

circuit boards from mobile phones and computers. Waste Management, 31,

25532558 (2011).

[7]Havlik T., Orac D., Petranikova M., Miskufova A., Hydrometallurgicaltreatmentof used printed circuit boards after thermal treatment. WasteManagement, 31,1542-1546 (2011).

[8]Liang G., Mo Y.W., Zhou Q.F., Novel strategies of bioleaching metalsfromprinted circuit boards (PCBs) in mixed cultivation of two acidophiles.

Enzymeand Microbial Technology, 47, 322-326. (2010).

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