Electrochemical removal of nickel ions from industrial wastewater

The electrochemical reduction of nickel ions in dilute industrial wastewater from a galvanic nickel plating plant was carried out on a three-dimensional electrode in a gas diffusion electrode packed bed electrode cell (GBC) and also on a rotating disc electrode. To explain the experimental results, concentration profiles for selected species were calculated during nickel deposition. It was found that, depending on the solution composition and electrolysis conditions, metallic nickel, nickel oxide and nickel hydroxide, as well as nickel oxyhydroxide, can be deposited. Metallic nickel dendrite formation and 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 found 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.