Peracetic acid combined with ultraviolet for ibuprofen degradation: Activation mechanism and reactive species contribution

As an emerging advanced oxidation technology, ultraviolet/peracetic acid (UV/PAA) shows great potential in removing pharmaceuticals and personal care products (PPCPs) in the field of wastewater treatment. In this work, ibuprofen (IBP) was chosen as the contaminant to study the degradation effects and PAA activation mechanisms by UV irradiation. The experimental results showed that UV/PAA had an excellent degradation efficiency (99.22 %) of IBP after 15 min reaction, and the synergistic effect between UV and PAA was also observed. Increasing the dosage of PAA caused the increase in IBP degradation reaction rate. Under acidic conditions, the increase in pH values increased the degradation reaction rate, whereas the opposite was true in alkaline conditions. In addition, the coexisting substrates (e.g., NO3-, CO32-, Ca2+, and HA) could exert inhibition on the degradation. Quenching experiments were carried out using various quenchers to identify reactive oxygen species (ROSs) in the system. The results demonstrated that ·OH and carbon centered radicals (R-C·) played a dominant part in the degradation, and the contribution of CH3C(O)OO·,·O2-, CH3C(O)O·, ·OH, and direct photolysis were estimated to be 29.9 %, 26.9 %, 21.5 %, 14.5 %, and 7.2 %, respectively. The results of IBP intermediates identification indicated that the degradation process was mainly related to its side chain decarboxylation, oxidative dehydrogenation, demethylation, and the oxidation of the aromatic ring. Furthermore, Toxicity Estimation Software Tool (T.E.S.T.) and ECOSAR were applied to evaluate the toxicity of the intermediate products was further evaluated. This study enriched the understanding of the PAA activation mechanism by UV involved, and improved the theory and technology of removing PPCPs by UV/PAA process.