Electrochemical reduction of nickel ions from dilute solutions

Electrochemical reduction of nickel ions in dilute solution using a divided GBC-cell is of interest for purification of waste waters. A typical solution to be treated is the effluent from steel etching processes which contain low quantities of nickel, chromate and chromium ions. Reduction of chromate in a divided GBC-cell results in effluent containing Cr3+ ions. This paper examines the limitations to further treatment of the effluent by electrochemical reduction of nickel ions. Nickel current efficiency has been determined by varying temperature, pH, current density and concentration of supporting electrolyte. It was found that the presence of a complexing agent, e.g. NH4 + is necessary. To deposit nickel, complete removal of Cr3+ ions from the solution is inevitable. Optimum nickel current efficiencies are obtained at pH 5 and current density 10 mA cm–2