Highly efficient Au recovery from acidic E-waste leachate using electrochemical nickel membrane reactor

Electrochemical recovery of gold (Au) from acidic electronic waste (e-waste) leachate has attracted growing interest, yet its practical application is constrained by excessive energy demand, limited recovery efficiency, anode instability, and poor selectivity. Here, an electrochemical Ni membrane reactor modified with Cu nanoparticles (Cu/eNMR) was developed to overcome these challenges. The Cu/eNMR achieved complete Au recovery with a unit energy consumption of only 0.13 kWh/g_Au from acidic solution containing 20 mg/L AuCl₄^- (pH = 2), compared with 77.1 % recovery and 0.36 kWh/g_Au Au for the Cu-based conventional electrochemical reactor (Cu/CER). High selectivity was attained in the presence of Cu²⁺ and Ni²⁺, enabled by less negative cathodic potentials that suppress hydrogen evolution and competing metal reduction. Physical separation of the leachate from the anode further improved stability, preventing proton- and chlorine-induced degradation observed in CER. Mechanistic studies indicated that Au recovery proceeds through direct electron transfer from the external circuit, distinct from the hydrogen atom diffusion pathway reported in Pd-based electrochemical membrane reactors. Selective Au recovery and separation were also demonstrated with real central processing unit (CPU)-derived leachate. Techno-economic analysis confirmed the potential of Cu/eNMR as a reliable and cost-effective strategy for sustainable Au recovery.