Kinetics and mechanisms of DMSO (dimethylsulfoxide) degradation by UV/H2O2 process

Abstract

The objective of this study was to elucidate the degradation pathways of dimethylsulfoxide (DMSO) during its mineralization caused by UV/H 2O2 treatment. In order to accomplish this, we measured the concentration time-profiles of DMSO and its degradation intermediates during the UV/H2O2 treatment. In addition, we proposed a kinetic model that could account for the degradation pathways of DMSO during its UV/H2O2 treatment. The results show that the degradation of DMSO by the UV/H2O2 treatment can be classified into two major pathways, and this is supported by both the analysis of the intermediates and total organic carbon (TOC) measurements. Firstly, DMSO was degraded into sulfate (SO4 2-) through the formation of methansulfinate (CH3SO2 -) and methansulfonate (CH3SO3 -) as sulfur-containing intermediates. One of the two carbon constituents of DMSO was highly resistant to mineralization, due to the formation of methansulfonate, which reacted very slowly with •OH (k=0.8×107M-1s -1). Secondly, the other carbon constituent of DMSO was relatively easily mineralized through the formation of formaldehyde (HCHO) and formate (HCO2 -) as non-sulfur-containing intermediates. The kinetic model proposed in this study for the degradation of DMSO by •OH in the UV/H2O2 process was able to successfully predict the patterns of concentration time-profiles of all components during the UV/H2O2 treatment of DMSO.