Technology for the Purification of Electroplating Washwater from Cadmium Ions by Membrane and Membraneless Electrolysis

A technology for removing toxic Cd 2+ from electroplating process electrolytes and washwater containing or Cl – is proposed. This technology makes it possible to decrease the concentration of Cd 2+ in treated solutions to 0.1–0.07 g/L and the Cd 2+ ingress into plant waste waters by 288–366 times and attain a Cd 2+ recovery of 99.7%. Electrolysis in a dual-chamber cell with an anion-exchange membrane makes it possible to return Cd and a H 2 SO 4 solution back into the process. The removal of Cd 2+ from Cl – containing solutions is recommended to be performed by membrane electrolysis, separating the insoluble anode with a chemically stable cation-exchange membrane to prevent the migration of Cl – from the catholyte into the anolyte and, correspondingly, their oxidation on the insoluble anode with the liberation of toxic Cl 2 .