مجتبی اسماعیل زاده

PCB recycling is crucial due to the growing electronic waste, which poses significant environmental hazards from hazardous materials like heavy metals. Traditional recycling methods, involving strong acids and high temperatures, generate toxic chemical waste and release hazardous fumes. As a result, it is essential to investigate green alternatives to reduce these environmental hazards. This study investigates the recovery of copper from waste printed circuit boards (PCBs) using a green, oxidant-free two-component deep eutectic solvent (DES) composed of choline chloride and malonic acid (ChCl: MOA), without an oxidant agent. The influential parameters-temperature, leaching time, PCB/DES mass ratio, and agitation speed-were optimized using Taguchi method, revealing that higher temperatures and longer leaching durations significantly enhance copper extraction. Analysis of variance (ANOVA) confirmed that temperature, leaching time, and PCB/DES ratio as statistically significant factors, whereas agitation speed had a negligible impact within the studied range. According to the optimization evaluation, maximum copper recovery of 89.5% was achieved under conditions of 100 °C temperature, 360-min leaching time, 0.04 g/g PCB/DES ratio, and 200 rpm agitation speed. Complete recovery was observed for Ag, while Sn showed a moderate recovery of 77.2%, which attributed to its alloying with copper and its limited dissolution in DES. Cu2+ forms stable [CuCl4]2– complexes in the ChCl: MOA DES via strong first-shell coordination with Cl–, as confirmed by molecular dynamics (MD) simulations and UV–Vis spectroscopy. RDF and coordination number analyses reveal a negligible interaction between Cu2+ and MOA. Additionally, hydrogen bonding is dominated by ChCl–Cl– interactions, while MOA is primarily involved in intramolecular hydrogen bonding, limiting its contribution to solvation and metal coordination after leaching.