Recovery of precious metals from waste electronics by biosorption

Continuous improvement of technology promotes the consumption and circulation of the electrical and electronic equipment and as a result, large quantity of waste has increased rapidly. In the hierarchical procedure for an integrated and sustainable WEEE management, material recovery has an inner importance. In this thesis, recovery of materials from WEEE is handled and, recovery of precious metals from printed circuit boards (PCB), a type of WEEE, is aimed. In Turkey, 539,000 tonnes of waste electronics are generated each year and 3.1% of them are constituted by PCBs. PCB production needs to use of some precious metals, which have limited reserves and require sizeable investment to obtain. These metals are compromised by 18.4% copper (Cu), 0.16% silver (Ag), 0.04% gold (Au) and 0.01% palladium (Pd) by weight. In this thesis, it is aimed recovery of precious metals (Cu, Ag, Au and Pd) in PCBs by biosorption, differently from traditional methods. Orange peels, which is an organic waste that occurs in high quantity and can only be used animal feed, were used as the biosorbent. In the study, firstly orange peels were modified by different methods in order to increase the adsorption capacity. Then, Cu, Ag, Au and Pd model solutions were prepared. Secondly, biosorption tests on the model solutions were carried out by modified/unmodified orange peels. At the last stage, biosorption studies on leach solution of solid product obtained from PCB pyrolysis were carried out by using the best biosorbent which were defined by the adsorption results of the model solutions, and as a result, recovery of metals from PCBs was achieved at high rate. Keywords: Biosorption, Orange peel, Precious metal, Printed circuit board, Waste electronic equipment.