TREATMENT OF NICKEL-CONTAINING WASTE WATER ON PHOSPHATING

摘要

Production of a nickel-containing solution consisting of a phosphating bath overflow and/or rinsing water comprises phosphating using an acidic phosphatizing solution containing 3-50 g/l phosphate ions, 0.2-3 g/l zinc ions, 0.01-2.5 g/l nickel ions and optionally further metal ions and an accelerator. The bath overflow and/or the rinsing water is passed over a weakly acidic ion exchanger after phosphating. The acid groups of the ion exchanger are neutralized to not more than 15 % with alkali metal ions. The nickel-containing aqueous solution has a pH of 2.5-6.0 on charging to the ion exchanger. Preferred Features: The bath overflow and/or the rinsing water is subjected to membrane filtration in the form of ultrafiltration, nanofiltration, reverse osmosis or other filtering process, and the aqueous solution is fed over the ion exchanger after filtering. The weakly acidic ion exchanger binds nickel ions stronger than zinc ions. The ion exchanger supports chelate-forming iminodiacetic acid groups.