Sustainable cobalt leaching using in-situ CoO reduction: a microwave-driven solution for complex ores

This study presents a green cobalt extraction method from Zebesha ore in Zambia, combining carbothermic reduction with microwave-assisted leaching (MWL) and conventional leaching (CL). Ore mixed with 20 wt.% charcoal was roasted at 650 °C for 1.5 h in air, reducing Co₂O₃·H₂O to CoO. A 1:1 mixture of roasted and unroasted ore was leached under MWL and CL conditions. The CoO in the roasted portion served as an in-situ reductant, converting Co3⁺ to Co2⁺ in the unroasted ore. MWL achieved 98.0% cobalt extraction in 30 min, compared to 96.5% in 180 min for CL. This method eliminates sodium metabisulphite, avoiding harmful sodium sulphate byproducts. The approach provides a sustainable, low-energy route for cobalt recovery from both primary ores and secondary resources such as spent lithium-ion batteries.