Abstract
All surface treatment waste water except concentrated waste solutions from pre-treatment, plating, and post-treatment has been separated into acid-alkaline, chromic, and cyanide waste water, mixed after chromium reduction and cyanide oxidation, and treated a process that generate large amounts of sludge. Components cannot be completely separated and recovered from such water even if methods like ion-exchange are used. Considering environmental protection and effective use of resources and energy, process components should be recovered, regenerated, and recycled for each process in non waste water treatment. Using electrodialysis (ED) under the proper conditions (electrode solution, voltage, flow rate, membrane distance, number of compartment, etc.), spent plating solutions are concentrated and desalted for recycling as plating solutions and water. ED treats plating solutions at room temperature and requires no energy except electric power, no chemicals for separating components, and no membrane regeneration making it applicable to plating recycling. We constructed ED installations and studied the recovery of metals and water from copper sulfamate/nickel sulfamate multilayer alloy plating baths. We effectively recovered copper, nickel and water with an ED installation having a membrane distance of 5mm and operated using 0.05M sulfamic acid as the electrode solution at 7.5V.
