Treatment of nickel plating waste

grantor: University of TorontoTreatment of spent nickel plating solution was performed by a novel alkaline chlorination technique, using an aqueous solution of sodium hypochlorite. It was established that ammonia was the primary complexing agent preventing metal precipitation, while sodium citrate was only a weak complexing agent Alkaline chlorination was used to destroy ammonia and deactivate sodium citrate in the plating solution. Once ammonia was removed, the buffering and complexing ability of sodium citrate was overcome by the alkalinity from hypochlorite addition. By raising the pH of the solution further, nickel was recovered as a nickel hydroxy oxide. A stoichiometric equilibrium model, a multiphase multispecies Gibbs free energy minimization program was setup to describe the behavior of different species in the system. The results of the model were consistent with experimental results. It is concluded that alkaline chlorination can provide excellent recovery of nickel from spent plating solution.M.A.Sc