Conceptual Process Design and LCA Evaluation of Precious Metals Recovery from Waste PCBs

The present study explores the development and evaluation of precious metals (PM) recovery processes designed to extract silver (Ag), gold (Au), and palladium (Pd) from copper anode slimes (CAS) generated via the black copper route from waste printed circuit boards (PCBs). Two conceptual process flowsheets—Route 1 (conventional) and Route 2 (polar aprotic solvent)—were designed and simulated adopting established and novel metallurgical methods using FactSage™ and HSC Chemistry 10 software. Both routes employed leaching-precipitation techniques; however, Route 1 utilized conventional acid-salt precipitation methods, whereas Route 2 incorporated with a novel approach based on polar aprotic solvent leaching. The results showed that the simulated recovery rates for Ag, Au, and Pd were high across both processes, achieving 94.8%, 99.1–99.3%, and 99–99.2%, respectively. To evaluate the environmental impacts, a life cycle assessment (LCA) was conducted using openLCA, with the treatment of CAS in kg as the functional unit and a gate-to-gate system boundary. It was found that Route 1 had lower environmental impact potentials, yielding acidification potential (AP) of 0.52–0.93 kg SO₂ eq, eutrophication potential (EP) of 0.67–1.21 kg PO₄ 3⁻ eq, and global warming potential (GWP) of 61.83–110.4 kg CO₂ eq. Conversely, Route 2 exhibited higher AP (0.59–1.26 kg SO₂ eq), EP (0.7–1.33 kg PO₄ 3⁻ eq), and GWP (75.1–134.9 kg CO₂ eq), primarily due to the use of CuCl₂, DMF, and ethanol in the Au and Pd recovery steps.