An integrated microwave-ultraviolet catalysis process of four peroxides for wastewater treatment: Free radical generation rate and mechanism

Abstract

The Advanced Oxidation Processes (AOPs) still require further research in response to ever-increasing standard of reclaimed water reuse and operating environment requirements. In this study, an efficient microwave-ultraviolet catalyzed oxidation system (MW-UV) was successfully developed, and its degradation effect was studied by using activated H2O2, sodium percarbonate (SPC), persulfate (PS), and peroxymonosulfate (PMS) to degrade toxic organic contaminants in wastewater and actual industrial wastewater. It was shown that MW-UV had an exceptionally high capability to react with these four common peroxides to produce reactive radicals (OH and SO4−). This can destroy multiple toxic organic contaminants through nonselective oxidation with a wide range of pH applications, has strong adaptability to anions in bodies of water, and can effectively treat wastewater. The sequence of predominant free radical generation rate by MW-UV was SPC > H2O2 > PS > PMS, with higher generation rate constant than other Fenton processes. The free radical evolution mechanisms for H2O2, SPC, PS, and PMS activation were also investigated. The thermal and non-thermal effects of microwave irradiation have a significant enhancement for UV reactions, and thus the synergy between the MW and UV can effectively activate peroxide. This treatment method could provide scientific basis and reference for degrading toxic organic contaminants in small-scale and limited space wastewater treatment.