Recovery of molybdenum, nickel and cobalt by precipitation from the acidic leachate of a mineral sludge

ABSTRACTThe objective of this study was to investigate the recovery potential of molybdenum (Mo), nickel (Ni) and cobalt (Co) from synthetic and real acidic leachate of a mineral sludge from a metal recycling plant by sulfide precipitation. The operational parameters (metal sulfide (M/S) ratio 0.1–1, agitation speed 0–100 rpm, contact time 15–120 min and pH 1–5) were optimized in batch conditions on synthetic metal leachate (0.5 M HNO3, Mo = 101.6 mg L−1, Ni = 70.8 mg L−1, Co = 27.1 mg L−1) with a 0.1 M Na2S solution. Additionally, recovery of the target metals was theoretically simulated with a chemical equilibrium model (Visual MINTEQ 3.0). The optimized Na2S precipitation of metals from the synthetic leachate resulted in the potential selective recovery of Mo at pH 1 (98% by modeling, 95% experimental), after simultaneous precipitation of Ni and Co as sulfide at pH 4 (100% by modeling, 98% experimental). Metal precipitation from the real leachate (18 M H2SO4, Mo = 10,160 mg L−1, Ni = 7,080 mg L−1, Co =...