Highly efficient removal of organic pollutants via a green catalytic oxidation system based on sodium metaborate and peroxymonosulfate

Abstract

The development of highly efficient and green catalytic oxidation process based on peroxymonosulfate (PMS) activation has been identified to be a significant yet challenging objective in the environmental catalysis field. A simple, environmentally benign and highly effective catalytic oxidation system was innovatively constructed by coupling NaBO2 and PMS for the removal of Acid Red 1. The catalytic mechanism in the NaBO2/PMS system was elucidated by electron paramagnetic resonance (EPR) combined with several radical capture reagents (ascorbic acid, methanol, tert-butyl alcohol, ethanol and l-histidine). The experimental results indicated that singlet oxygen (1O2) severed as the predominant reactive oxygen species (ROS) rather than the HO or ▪ during the catalytic oxidation process, at variance with the reported radical pathway in the Co2+/PMS system. Inspiringly, p-benzoquinone (p-BQ) as a trapping agent in most advanced oxidation process could be turned into the positive one in the NaBO2/PMS system, achieving a nearly 3-times enhancement in terms of the rate constant for AR1 removal. More interestingly, sodium chloride (NaCl) presented the same enhancement effect as p-benzoquinone due to generation of hypochlorous acid (HOCl) and more 1O2, which was completely different from the reported. This study develops a highly efficient green oxidation process and opens up a new insight in the remediation of contaminated water.