Investigation of new reagent systems for recovery of metals from electronic wastes

In this thesis, new reactive systems were investigated to recover metals from waste printed circuit boards (WPCBs), the most important component of e-waste with significantly high content of base and precious metals compared to ores. High copper extractions (up to 93.5%) was achieved in peroxide assisted methanosulfonic acid (MSA) leaching in which the beneficial effect of increasing H2O2 (up to 2.00 M) and MSA (0.2-1.00 M) concentrations was observed in contrast to the adverse effect of temperature (20-60℃) on copper leaching. In the peroxide assisted glycine leaching, increasing glycine concentration (1.00-2.00 M) exerted a negative effect on the extraction of copper whilst it improved with increasing H2O2 concentration (0.50-4.00 M) and temperature (20-60℃). As an alternative to peroxide, Na2S2O5/O2(air) was tested in the glycine leaching, resulting in the improved copper extractions. Solvent Displacement Crystallization (SDC) method was studied for the recovery of copper from pregnant leach solutions of both MSA and glycine leaching systems. The highest copper precipitation efficiency was determined as 88.8% with acetone in the MSA leaching system. Copper precipitation efficiencies of 96.8% and 99.5%, respectively, from peroxide and Na2S2O5/O2(air) systems of glycine leaching were obtained using 2-propanol. These findings have demonstrated the development and application of an environmentally benign and effective hydrometallurgical process based on MSA and glycine as alternative to inorganic acids.