Effect of ionic liquid [MIm]HSO₄ on WPCB metal-enriched scraps refined by slurry electrolysis

Waste printed circuit boards (WPCBs) are usually dismantled, crushed, and sorted to WPCB metal-enriched scraps, still containing an amount of non-metallic materials. This research used slurry electrolysis to refine these WPCB metal-enriched scraps and to examine if a standard ionic liquid, [MIm]HSO₄, can replace H₂SO₄ in the system. The impact of the refinement process on metal migration and transformation is discussed in detail. The results demonstrated that metals in WPCB metal-enriched scraps could be successfully refined using slurry electrolysis, and [MIm]HSO₄ can be used to replace H₂SO₄ in the system. When 80% of H₂SO₄ was replaced by [MIm]HSO₄ (electrolyte of 200 mL, 30 g/L CuSO₄·5H₂O, 60 g/L NaCl, 130 g/L H₂SO₄, and 1.624 A for 4 h), the total metal recovery rate is 85%, and the purity, current efficiency, and particle size of cathode metal powder were 89%, 52%, and 3.77 μm, respectively. Moreover, the microstructure of the cathode metal powder was dendritic in the H₂SO₄-CuSO₄-NaCl slurry electrolysis system, whereas at an 80% [MIm]HSO₄ substitution rate slurry electrolysis system, the cathode metal powder was irregular and accumulated as small-sized spherical particles. Thus, replacing inorganic leaching solvents with ionic liquids may provide a potential choice for the resources in WPCB metal-enriched scraps.