INHIBITION OF NICKEL PRECIPITATION BY GLUCONATE - I - KINETIC-STUDIESAND SPECTROSCOPIC ANALYSES

The role of gluconate on nickel precipitation kinetics was evaluated t hrough particle size distribution analyses, and the inhibition mechani sms were explored through spectroscopic studies. Batch kinetic studies showed that nickel precipitation does not achieve equilibrium within the time frame of typical process units. The molar ratio of gluconate to nickel had a profound effect on precipitation kinetics. A complete inhibition of nickel precipitation was observed when the molar concent ration of gluconate was high, and a time-dependent resolubilization wa s observed at lower ratios. Particle size distribution indicated that nickel precipitates were colloidal in nature. Nucleation rates were pr omoted by the presence of gluconate; however, the removal efficiency d ecreased due to complexation reactions. Spectroscopic analysis of the solids suggested the presence of a mixture of two solids, a nickel-glu conate complex and a nickel hydroxide. The kinetics of the formation o f the precipitates suggests that design of treatment units for the rec overy of nickel in the metal finishing industry should be proceeded wi th advanced oxidation that would oxidize the organic impurities, befor e nickel recovery is accomplished.