ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Highly efficient and selective removal of copper from low pH nickel Watts solution through hydrogen sulfide

Xiaofeng Lu, Yijing Li, Aijun Zhang, Guoying Luo, Xu Wu, Shirong Wang, Jianhua Feng, and Yong Guo

Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, People’s Republic of China

E-mail: luxf@licp.cas.cn

Received: 16 January 2023  Accepted: 10 July 2023

Abstract:

Cu-removal operation is one of the vital purifying processes for the nickel electrolysis anolyte. Different from the nickel concentrate-activated anode slime-sulfurous acid, NiS and MnS, hydrogen sulfide (H₂S) introduced less metal impurities into the systems. And the precipitation theory is the main principles of nickel purification method utilizing H₂S in removing Cu from the anolyte rather than these replacement reactions. The Solubility Product Constant (K_sp) of CuS is lower than NiS, which indicates that the precipitate of CuS can be highly efficiently and selectively formed and easily removed from the nickel anolyte. In this research, the effects of mole ratio of [H₂S]/[Cu], pH, temperature, potential–pH diagrams and the precipitates of metal sulfides were investigated. The experimental results show that the H₂S was a potential successor as the highly efficient and selective Cu-removal reagent. The concentration of Cu²⁺ in Watts can be reduced to lower than 0.002 g/L, and the mass ratios of Cu/Ni in this precipitate are larger than 15 in the low pH state (1.0–1.5). S, CuS, Cu₂S, NiS, NiS₂ or Ni₃S₂ may be presented and coexisted in the region that concluded from the analysis of potential–pH diagram. The XRD analysis of precipitates indicated that it was composed by CuS and NiSO₄·6H₂O. The XPS measurement shows that the valence states of Cu and Ni are Cu²⁺ and Cu⁺ and Ni²⁺, respectively. The valence state of S includes the S²⁻, S_x²⁻ and SO₄²⁻ states. Therefore, H₂S can highly efficient and selective remove the Cu²⁺ from the low pH nickel Watts solution, and which can be applied on the nickel anolyte purification in the future.

Graphical abstract

Keywords: Chemical precipitation method; Nickel Watts baths; Copper removal; Gas–liquid reaction; Metal sulphide

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-023-02970-6

Chemical Papers 77 (11) 6707–6715 (2023)