Targeted recovery of Ag-Pd alloy from polymetallic electronic waste leaching solution via green electrodeposition technology and its mechanism

Abstract

Electronic waste (e-waste), as hazardous waste, is a promising secondary resource of precious metals. The extraction of precious metals from e-waste has great environmental and economic benefits. Most of the existing methods have high energy consumption, environmental pollution or low recovery efficiencies. This study proposed the application of green electrodeposition technology to realize targeted recovery of Ag-Pd alloy from Ni, Cu, Ag, Pd, Bi polymetallic e-waste leaching solution. Linear sweep voltammetry was conducted to determine the feasibility of targeted extraction. The high purity of Ag-Pd alloy was realized by controlling the potential. The recovery efficiencies of Ag and Pd were 97.72% and 98.05% after 5 h in 0.5 mol/L HNO3 with applied potential of 0.35 V. The results indicated the formation of monophase Ag-Pd alloy. Besides, the effect of acidity and potential on the particle size of alloy was analyzed. Chronoamperometric method was applied to study the electrodeposition mechanism. The Ag-Pd electrodeposition followed three-dimensional instantaneous nucleation and growth mechanism analyzed with Scharifker-Hills model, thus producing a solid solution. The nucleation site increased with the overpotential. This study provides a novel, efficient and green approach for the targeted recovery of Ag and Pd from the complex multi-metal system of e-waste.