Selective leaching of Cu and Co from stratiform sediment-hosted copper ore using deep eutectic solvents

• Deep eutectic solvents (DESs) tested for Cu and Co leaching from Cu ore. • Cu leached from malachite using acid, Co in cuproasbolane requires a reducing agent. • DES leaching conducted at 20–80 °C; greatest Cu and Co selectivity found at 20 °C. • ChCl–lactic acid has comparable Cu and Co leaching efficiency to H 2 SO 4 with FeSO 4. • ChCl–lactic acid has the greatest selectivity for Cu and Co. Hydrometallurgical processing of sediment-hosted stratiform Cu ores traditionally relies on strong, often toxic mineral acids, with a primary focus on Cu recovery. Cobalt, an important but frequently overlooked byproduct, is typically recovered with poor efficiency (e.g., ∼45 %). To address this knowledge gap, we investigated the simultaneous leaching of Cu and Co from a Cu ore from the Central African Copperbelt using oxalic, formic, and lactic acid-based choline chloride (ChCl) deep eutectic solvents (DESs). Results were compared with conventional leaching using sulfuric acid (10 g/L), both with and without ferrous sulfate (1.5 g/L). Across the temperature (20–80 °C) and time (1–90 h) ranges studied, all DES formulations achieved leaching efficiencies comparable to those of sulfuric acid. Choline chloride–lactic acid (ChCl:LA) exhibited the best overall performance, yielding higher selectivity for Cu and Co. This was most pronounced at 20 °C, where, after 90 h, 94 % and 85 % of Cu and Co were respectively leached, but only 5 % of the Fe was dissolved, compared to 96 %, 76 % and 9 % recorded for sulfuric acid. These findings highlight the potential of DESs, particularly those composed of hydrogen bond donors with chelating and reducing properties, such as ChCl:LA, as highly promising alternatives for Cu and Co leaching from stratiform sediment-hosted Cu ores.