Selective leaching of copper and zinc from seafloor massive sulfides using methanesulfonic acid

Seafloor massive sulfides (SMS) represent promising resources of copper (Cu) and zinc (Zn), but their polymetallic mineralogy complicates conventional pyrometallurgical treatment. This study evaluates methanesulfonic acid (MSA), a low-corrosive and non-volatile organic acid, as a lixiviant for SMS ore composed of chalcopyrite (CuFeS 2 ), sphalerite (ZnS), pyrite (FeS 2 ), and anglesite (PbSO 4 ). Shake-flask leaching tests were performed under varied MSA concentrations (0–40 g/L), temperatures (20–70°C), pulp densities (1–10%), and H 2 O 2 dosages (0–5%). At 30 g/L MSA, 60°C, and 1% pulp density, >40% of Cu and Zn were leached within 3 days, while Pb and Fe dissolved at 32% and 17%, respectively. Adding 1% H 2 O 2 increased Cu and Zn leaching to >75% and raised Fe dissolution to 39%, while suppressing Pb dissolution to <2.5% due to re-precipitation as PbSO 4 . Kinetic analysis (20–70°C) indicated shrinking-core behavior, where CuFeS 2 dissolution was best described by a product-layer diffusion model but exhibited a relatively high apparent activation energy (56.1 kJ/mol), suggesting a notable contribution from interfacial chemical reactions. In contrast, ZnS showed mixed diffusion–reaction control with a lower activation energy (31.6 kJ/mol). Chloride effects were examined under industrially relevant conditions (10% pulp density, 30 g/L MSA, 1% H 2 O 2 , 45°C). Addition of 2% NaCl or synthetic seawater increased Cu dissolution from 45% to 56% in 15 days, while Zn remained largely unchanged. Cl⁻ likely promoted CuFeS 2 dissolution via stabilization of intermediate Cu oxidation states and Cu–Cl complexation, and simultaneously reduced Fe dissolution to <4% due to jarosite formation. This study provides the first detailed evaluation of MSA for SMS ore leaching, demonstrating its potential as an environmentally compatible alternative for hydrometallurgical processing of deep-sea mineral resources.