Study on transformation and removal of phosphorus species in the treatment of spent electroless nickel plating bath

Abstract

Aiming at the difficult-to-treat high-concentration phosphorus in the spent electroless nickel plating baths, the transformation trends of phosphorus species in catalytic oxidation-reduction, H2O2 oxidation, calcium hypochlorite oxidation, and Fenton oxidation treatment processes were monitored and analyzed. Subsequently, the coagulation/precipitation process was further used to remove TP from the wastewater, and the final TP removal effect was investigated. The experimental results showed that there was no obvious selectivity in the three oxidation treatments of H2O2 oxidation, calcium hypochlorite oxidation, and Fenton oxidation, and a certain concentration of difficult-to-treat H2PO2- remained in the wastewater after the reaction, with TP removal rates of 81.9%, 92.2%, and 96%, respectively. After catalytic oxidation-reduction treatment, almost all phosphorus species in the spent electroless nickel plating baths were converted to HPO32-, and the TP removal rate could reach 99.7% after calcium chloride precipitation treatment. Meanwhile, HPO32- was also a valuable resource that could be utilized. By adding Al2(SO4)3·18H2O to the wastewater treated by catalytic oxidation-reduction, aluminum phosphite products could be recovered, which was of great significance in wastewater treatment, green environmental protection and resource utilization.

Keywords

• spent electroless nickel plating baths
• catalytic oxidation-redox
• fenton oxidation
• phosphite