Investigation of the effect of electrolyte composition and nickel depassivating additives on the electrochemical behavior of nickel sulfide

Alexandr Kolesnikov, M. I. Natorhin, Е. И. Теруков, A. Zh. Suigenbayeva, A. A. Saipov

2020

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DOI 10.17073/0021-3438-2020-3-13-22
Data confidence 70 medium
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Abstract

This article deals with the hydrometallurgical technology of nickel sulfide (NiS) processing, in particular, the effect of electrolyte composition and depassivating additives on the electrochemical behavior of synthesized nickel sulfide. The kinetics and electrochemical behavior of nickel sulfide in sulfate, sulfite, chloride, bichromate, ammonia and copper-containing electrolytes were studied. Possible directions of the process of nickel sulfide anodic dissolution with the release of elemental sulfur and sulfides that contribute to surface passivation were shown. The depassivating effect of additives, in particular NaCl, KBr and K 2 Cr 2 O 7 was also studied. The results of studies suggest that: potassium bichromate has a depassivating effect on NiS anodic dissolution in Na 2 SO 4 and NH4OH; the optimum concentration of potassium bichromate is around ≈30 g/dm 3 ; sulfide sulfur oxidizes to SO 2 4- with NiS dissolution in the presence of K 2 Cr 2 O 7 ; NiS intensively dissolves in the pure Na 2 SO 3 solution with the formation of insoluble Ni 2+ hydroxy compounds featuring structure changes with changing pH; the combined action of NH 4 OH and Na 2 SO 3 causes intensive NiS dissolution with the formation of [Ni(NH 3 )n] 2+ ammonia complexes; the presence of acid anions capable of complexation with both Cu(I) and Cu(II) in copper-containing electrolytes leads to accelerated NiS anode dissolution; the most significant anode dissolution rates are observed in case of a nitrate-bromide system; molten sulfur formed on the NiS surface completely displaces, and copper-bromide complexes dissolve the Cu 2 S film formed at low potentials; when 200 g/dm 3 of KBr is added to 96.8 g/dm 3 of Cu (NO 3 ) 2 , greater NiS dissolution rates are observed than when 200 g/dm 3 of NaCl is added to 67,22 g/dm 3 of the CuCl 2 solution.