Abstract
Cobalt is a critical metal for rechargeable batteries and high-performance alloys, and its recovery from both primary and secondary resources is increasingly important in hydrometallurgy. Oxidative precipitation of cobalt (Co²⁺ to Co³⁺) provides a selective route for cobalt removal from acidic sulfate solutions. In this study, thermally activated sodium persulfate (Na₂S₂O₈) was evaluated as an oxidant for cobalt precipitation from synthetic sulfate media containing 5 g·L⁻¹ Co²⁺ at pH 4. Persulfate concentrations of 0.1, 0.2, and 0.5 mol·L⁻¹ were tested at 60, 70, and 80 °C. Cobalt removal was proven to strongly depend on both oxidant dosage and temperature. At 0.1 M, removal remained below 50%, whereas 0.2 M, >98% removal was achieved at 70–80 °C. Near-complete cobalt removal (≈100%) was obtained at 0.5 M with significantly reduced reaction times. X-ray diffraction confirmed the formation of cobalt oxyhydroxide (CoOOH) as the dominant precipitated phase. These results demonstrate that both temperature and persulfate dosage define practical operating ranges for persulfate-driven cobalt precipitation under hydrometallurgical conditions.