| Electroless plating technique has been widely used because of its unique advantages. However, the electroless plating bath is not stable due to its self reduction. Thus its usage life becomes short. The discarded bath often contains nickel, phosphate, sodium sulfate and organic matter COD. It is well-known that nickel is a carcinogenic heavy metal but also a short and expensive metal resource. Phosphorus in waste solution is one of the main polluting factors which may cause eutrophication. Therefore, it is of great importance to study on how to treat the spent electroless nickel bath to reclaim the resources and minimize the damage to the environment.In this study, the spent acidic electroless nickel plating bath containing hyphophosphorous is chosen as the studying object. Studies are conducted on the selection of complexation decomposition oxidant, reuse of nickel by precipitation and treatment of phosphorus. A feasible and economic method is proposed for the treatment of spent bath for electroless nickel plating based on oxidation-precipitation. The concentrations of nickel and phosphorus in the treated waste solution can meet the National Discharge Standards. Meanwhile, nickel and phosphorus are recovered.Parameters, including the amount of oxidant which affects the treatment of nickel and phosphorus, the amount of precipitant, reaction temperature, reaction time, pH and stirring, are optimized based on numerous experiments. By orthogonal test, optimized conditions were obtained, which are as follows: the amount of NaClO is 2000 ml/L spent bath, pH 1.0 for de-complexation, 60℃for oxidation temperature and pH 13.0 for precipitation. The nickel concentration after treatment is reduced to 0.35 mg/L from 7.56 g/L. The pH of the solution after removing nickel is adjusted to 6.0, followed by adding 140 g/L CaCl2 and stirred for 3 hours. The concentration of phosphorus can be reduced to 0.36 mg/L from 26.93 g/L. The nickel hydroxide obtained is dissolved in...
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