Electrochemical removal of nickel ions from industrial wastewater

The electrochemical reduction of nickel ions in dilute industrial wastewate r from a galvanic nickel plating plant was carried out on a three-dimension al electrode in a gas diffusion electrode packed bed electrode cell (GBC) a nd also on a rotating disc electrode. To explain the experimental results, concentration profiles for selected species were calculated during nickel d eposition. It was found that, depending on the solution composition and electrolysis c onditions, metallic nickel, nickel oxide and nickel hydroxide, as well as n ickel oxyhydroxide, can be deposited. Metallic nickel dendrite formation an d its growth towards and on the Nafion membrane were identified as a major problem in a cell with a small interelectrode gap due to the damage caused on the gas diffusion electrode (GDE) membrane assembly. Moreover, it was fo und that the nickel selectivity ratio depends on the total current density as well as on the Ni2+ concentration, and that the surface of the rotating disc electrode can be completely blocked by green nickel hydroxide deposit. (C) 2000 Published by Elsevier Science S.A.