Activation of peroxymonosulfate by phosphite: Kinetics and mechanism for the removal of organic pollutants

In this study, phosphite (HPO32−) was used as a novel activator to activate peroxymonosulfate (PMS) for acid orange 7 (AO7) removal. Under the optimized conditions, the decolorization efficiency of AO7 was 82.1% within 60 min with rate constant values (kobs) of 0.0301 min−1. Besides, effects of the solution pH and the co-existing inorganic anions including Cl−, HCO3−, HPO42− and SO42− on AO7 removal were also investigated. Except for SO42−, other examined co-existing inorganic anions displayed favorable effects on the removal of AO7. Furthermore, the mechanism for PMS activation by the HPO32− was deeply elucidated by radical scavenger including ethanol (EtOH), tert-butanol (TBA), l-histidine and tiron, and electron spin resonance (ESR) studies. It was proposed that singlet oxygen (1O2) would be the dominant reactive oxygen species (ROS) in the HPO32−/PMS system for contamination degradation at neutral pH condition. The findings of this study provided useful information for the application of the substances in industrial wastewaters to activate PMS for organic contaminants degradation and in particular for HPO32--rich electroplating wastewater treatment.