Recovery of Au and Cu from waste memory modules by electrolysis with hydrochloric acid-hydrogen peroxide system

Abstract

E-waste is regarded as a special kind of solid waste, because its core components-waste memory modules (WMMs)-contain a large amount of high-value metal resources. However, there has been little research on the green recycling of key metals in WMMs. The difficulty lies in finding out how to reduce or eliminate the secondary pollution caused by the massive use of chemicals, and to improve the resource recovery rate. Therefore, this study constructed three systems based on an electrochemical method, to explore the leaching effects and principles of Au and Cu under different conditions (voltage, temperature, acid concentration and molar ratio). A response surface methodology called Box-Behnken Design was employed to optimize the parameters. The results showed that compared with other additives or without additives, H2O2 has the best effect on selective leaching of Au and Cu from WMMs. Meanwhile, HCl + H2O2 + direct current (DC) is the best system for selectively leaching Au and Cu compared to HCl + DC and HCl + H2O2. Appropriate increasing voltage, temperature and HCl concentration could effectively increase Au and Cu leaching rate, while the increase of mole ratio might inhibit Au and Cu leaching. The response surface quadratic model showed that the significance of Au response values was: voltage > n(HCl/H2O2) > temperature. Under the optimal conditions of 4.1 V DC constant voltage, 40 °C, 8.9 mol/L HCl concentration and 45 M ratio of acid to oxidant, the leaching rates of Au and Cu were 98.87 % and 92.10 %, respectively. It is worth noting that the electrolyte was composed of only HCl + H2O2, and electron was used as an oxidizing agent for potential controlling, which had the advantage of using less non-toxic and non-corrosive chemicals. The research results can provide a basis and technical support for e-waste recycling.