Dissolution of brominated epoxy resin for environment friendly recovery of copper as cupric oxide nanoparticles from waste printed circuit boards using ammonium chloride roasting

Abstract

This work focuses on development of an environment benign approach for separation of brominated epoxy resin (BER) and recovery of copper (Cu) as copper oxide (CuO) from end-of-life waste printed circuit boards (PCBs). The typical Cu concentration in PCBs varies in the range of 60 kg/t – 270 kg/t of Cu, which is much higher than its respective mineral ores. In the present work, dimethylformamide (DMF) was used for dissolution of BER followed by roasting with ammonium chloride (NH4Cl) for recovery of Cu. Separation of BER provides better metallic surface exposer and mitigates the possibility of formation of toxic polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) during the roasting process. More than 97% of BER was separated from the PCBs using DMF as solvent at 140 °C. The investigation revealed that at reaction conditions, dry HCl vapour formed due to decomposition of NH4Cl, reacts with Cu in presence of air to form CuCl2. The solid residue obtained after roasting was subsequently treated with water for extraction of CuCl2. More than 93% Cu was extracted when the delaminate PCBs (DPCBs) was roasted at optimum conditions of temperature: 275 °C, NH4Cl dose: 300%, and time: 180 min. From the leached solution, Cu was precipitated using ammonia solution as precipitating agent, which subsequently calcined at 500 °C to obtain 98% pure CuO nanoparticles (NPs).