Recovery of Nickel in Sulfate Solutions with Hydrogen Sulfide at Moderate Temperature

Abstract

The effects of sulfate concentration, the composition of the solution, and additives which accelerate precipitation of nickel sulfide on the recovery of nickel and forms of sulfides have been investigated in order to recover Ni²⁺ from sulfuric acid leaching solutions by introducing ELS under atmospheric pressure. The percentage of precipitation of Ni²⁺ reached 86.4 % in a NiSO₄ solution (4.0 g Ni²⁺/dma). But in the presence of Na₂SO₄ (0.28 mol/dm³) or MgSO₄(0.25 mol/dm³), the recovery of Ni²⁺ increased to 99.1 and 98.1%, respectively. In th e case of Al₂(SO₄) (0.24 mol/dm3 as SO₄2-), however, the precipitation of Ni²⁺ remained at 86.3%and in addition, an induction period of 45 min was observed. These phenomena were interpreted as the progress of the sulfate complex formation and initial pH lowering by the hydrolysis of AP+. In the presence of CuSO₄, the precipitation was promoted and the precipitations of Ni²⁺ increased. Both Fe and Cu powders accelerated the precipitation and the induction period disappeared. On addition of Fe (2 gidma), Ni₃S₂ and Ni precipitated, whereas α-NiS, Ni, S₂, and α-Cu₂S were identified when Cu powder was introduced. By the addition of β-NiS and activated carbon, β-NiS was formed and the induction periods of 7∼8 mm were still observed. The calculated percentages of Ni²⁺ precipitation were agreed with the observed values, when the sulfate complex formation as well as pH buffer action of SO₄2- was considered in calculation.