Gold Recovery from WPCB Gold Finger Using Water-Soluble Organic Leaching Agent Sodium Dichloroisocyanurate

Abstract

The rapid increase in electronic waste emphasizes the urgent need for low-toxicity, highly selective gold recovery methods. This study introduces a novel water-soluble organic leaching system using sodium dichloroisocyanurate (DCCNa) dissolved in water to investigate the gold leaching efficiency from the gold fingers of waste printed circuit boards (WPCBs). The pregnant leach solution (PLS) was processed using stepwise extraction. The gold oxidation states and leaching pathway were confirmed through UV–Vis, XPS, and ESI-MS analyses. Under optimal conditions (pH 2, 3-h leaching time, DCCNa concentration of 40 mmol/L, and 25 °C), the DCCNa leaching system achieved a gold leaching efficiency of 96.4%, significantly outperforming other metals and demonstrating its excellent selectivity. Stepwise extraction of the PLS using Acorga M5640 and dibutyl carbitol (DBC) resulted in a gold extraction efficiency of 95.5%. DCCNa generates the strong oxidant HClO, which reacts with HCl to produce Cl2. Both HClO and Cl2 oxidize Au(0) to Au(I) and Au(III), forming [AuCl2]− and [AuCl4]− complexes, with Cl− originating from the hydrolysis of HCl. This study presents a safe, economical, and eco-friendly approach for the efficient and selective recovery of gold from WPCB gold fingers under laboratory conditions, which achieves the sustainable utilization of precious metals.