Efficient and eco-friendly gold extraction from electronic waste via thiosulfate electrochemical oxidation

Extracting gold from electronic waste not only benefits the environment but also alleviates the scarcity of precious metals. This work proposes a method of electrochemical anodic oxidation with thiosulfate (EAOS), which successfully extracts gold from discarded printed circuit boards (PCBs) and central processing unit (CPU) boards by replacing copper ammonia oxidation with electro-oxidation. Moreover, by leveraging the synergistic mechanism of interfacial electrochemical anodic oxidation and an applied electric field, the electrode potential for Au oxidation is reduced, facilitating the dissolution of Au and reducing the consumption of S 2 O 3 2- . The optimized S2O32--KCl-NH3 (SKN) system exhibits a 100 % dissolution rate for gold in PCBs and CPU at a low voltage of 0.6 V, with a mere 4.3 % consumption of S2O3 2- and a current efficiency as high as 80 %. Compared with the traditional S 2 O 3 2--Cu 2 + - NH 3 (SCN) system, the leaching rate is improved by 30.3 %, and the consumption of S 2 O 32- is significantly reduced by 61.3 %. EIS test confirm that the applied electric field accelerates the electron transfer rate and promotes the oxidative dissolution of gold. Furthermore, the shrinking core model fitting analysis and activation energy calculation indicate that the reaction is mainly controlled by the interfacial electrochemical reaction, suggesting that the dissolution of gold mainly occurs at the electrode interface. LSVEQCM and SEM provide direct evidence for the efficient dissolution of gold by this method. In conclusion, this study offers a new strategy for the high-value utilization of electronic waste and a promising approach for establishing a green, sustainable and low-cost gold extraction technology.