Recovery of Ni matte from Ni-bearing electroplating sludge

Abstract

In this study, a novel process for the recovery of Ni from Ni-bearing electroplating sludge (ES) is proposed, which involves the carbothermic reduction stage and smelting stage. In the reduction stage, the CaSO₄, Fe₂O₃, and NiO in the ES were reduced by carbon at 1000 °C, and the Ni₃S₂ and Fe₄Ni₅S₈(Ni-rich phases) were generated. After that, the reduced ES was mixed with SiO₂ and smelted at 1500 °C. During the smelting stage, Ni₃S₂ and Fe₄Ni₅S₈ were melted to form liquid Ni-Fe-S matte and separated from the molten slag by gravity. Finally, 58.5%Ni-13.8%Fe-27.7%S (in weight) matte and vitrified slag were obtained. The recovery ratio of Ni (97.2%) was much higher than that of Fe (14.7%). Besides, the Ni/Fe mass ratio of the ES was 0.7, while the ratio of the prepared matte was about 4.2. Therefore, the selective recovery of Ni was achieved. The obtained Ni matte can be used as the raw material for pure Ni or Ni-bearing chemicals.

Keywords: Electroplating sludge; Nickel recovery; Selective sulfurization.