Study On Technology Of Removing Copper From Nickel Electrolyte Solution

Nickel is the important metal materials of national economy construction, It is widelyused in the fields of mechanical, aviation, chemical and industry department ect. Nickel is theimportant strategic resources of the country. The vast nickel market make strict requirementsfor nickel products and quality.In the process of production of pure nickel,the purity of nickelelectrolyte play a decisive role in nickel quality. Heavy metal copper is the key to guaranteenickel quality must be removed from the nickel electrolyte.In order to fully understand the balance of various ions in solution, especially the equili-brium concentration distribution of Cu²⁺and Ni²⁺, so it is able to control technological condi-tions correctly. In this paper, according to relationships between the ion ligand complexes andthe thermodynamics, the equilibrium concentration of the copper, nickel-ligand complex solu-tion was analysed; the distribution conditions of Cu²⁺, Ni²⁺and coordination complexs ionswere calculated; and the NiS method and replacement deposition method were used to remo-ve copper to reach the requirements of nickel electrorefining.The research contents and experimental result of this article were as follows:1. The thermodynamic analysis and calculation of Cu-Ni-Cl-H2O system show that thecopper element mainly exists in form of Cu²⁺、CuCl+and CuCl2（aq）, the nickel element mainlyexists in form of Ni²⁺、NiC^l+、NiCl₂（aq）、NiCl₃^-and NiCl₄^2-in the nickel anode electrolyte.2. Based on thermodynamic analysis of removing copper process by NiS method and re-placement deposition method, removing copper with NiS and replacement deposition methodwere feasible.3. In the study of removing copper with NiS, the effects of the pH value, reaction time,reaction temperature, NiS aging time and the amount of NiS on copper-removing degree andthe mass ratio of copper to nickel were studied. The experimental results showed that: remov-ing copper with NiS will achieve the best result when the dosage of NiS is1.2times of theor-etical value, the pH value is3.5, the reaction time is2h and the reaction temperature is85℃.The copper concentration could be decreased below3mg/L in electrolyte solution and themass ratios of copper to nickel is more than20in the residue after removing copper and NiSstill keeps active after the aging time of6hours, which reached the requirements of nickelelectrorefining. No harmful ions enter into the nickel anode electrolyte.4. The effects of solution pH value, reaction time, reaction temperature, S excessive mu-ltiples on copper-removing degree and the mass ratio of copper to nickel were studied in theprocess of copper removal with replacement deposition method. The experimental results sho- wed that: removing copper with replacement deposition method will achieve the best resultwhen the dosage of S is1.2times of theoretical value, molar ratio Ni to Cu is1, the pH valueis2.5, the reaction time is1.5h and the reaction temperature is90℃. The copper concentrati-on could be decreased below3mg/L in electrolyte solution and the mass ratios of copper tonickel is more than20in the residue after removing copper which reached the requirements ofnickel electrorefining.