Treatment of nickel containing industrial effluents with a hybrid process comprising of polymer complexation ultrafiltration electrolysis

A process was studied at the laboratory level and on a pre-industrial pilot for pollutant removal from industrial waste waters containing nickel cations. Five successive steps are involved: (1) complexation of the metal by means of polymeric ligands; (2) ultrafiltration of the complex, which produced a purified effluent and a concentrated metal complex solution; (3) decomplexation by acidification; (4) ultrafiltration of the concentrate after acidification allowing the recycling of the complexing agent; (5) electrolysis of the concentrated nickel solution (filtrate). A polycarboxylate and a polyethylenimine were investigated as complexing agents in a laboratory pilot, which lead to high rejection of nickel, even in the presence of salts such as NaCl or NaNO3. The decomplexation of polyethylenimine appeared to be too slow to be of practical interest for industrial use. The performances of several different membranes with polycarboxylate-nickel complexes were compared in a pre-industrial pilot and the operating parameters (temperature, pressures, liquid rate) were optimised. Starting from nickel at 60 mg l(-1), volume concentration factors up to 20 were shown to be of practical interest. Acidification and diafiltration of the concentrate afforded Ni(II) solutions which could be easily electrolysed while the complexing agent could be recycled to the beginning of the process. (C) 2000 Elsevier Science B.V. All rights reserved.