Degradation kinetics and disinfection by-products formation of benzophenone-4 during UV/persulfate process

The degradation kinetics, reaction pathways, and disinfection by-products formation of an organic UV filter, benzophenone-4 (BP4) during UV/persulfate oxidation were investigated. BP4 can hardly be degraded by UV alone, but can be effectively decomposed by UV/persulfate following pseudo-first order kinetics. BP4 degradation rate was enhanced with increasing persulfate dosage and decreasing pH from 8 to 5. However, the degradation rate of BP4 at pH 9 was higher than that at pH 8 because of the presence of phenolic group in BP4 structure. and SO4-& sdot; were confirmed as the major contributors to BP4 decomposition in radical scavenging experiments, and the second-order rate constants between HO & sdot; and BP4 as well as those between SO4-& sdot; and BP4 were estimated by establishing and solving a kinetic model. The presence of Br- and humic acid inhibited the decomposition of BP4, while NO3- promoted it. The mineralisation of BP4 was only 9.1% at the persulfate concentration of 50 mu M. Six degradation intermediates were identified for the promulgation of the reaction pathways of BP4 during UV/persulfate oxidation were proposed as a result. In addition, the formation of DBP in the sequential chlorination was evaluated at different persulfate dosages, pH values, and water matrix. The results of this study can provide essential knowledge for the effective control of DBP formation with reducing potential hazard to provide safe drinking water to the public. Highlights:center dot BP4 can be effectively degraded by UV/persulfate process, following pseudo-first order kinetics.center dot OH & sdot; and SO4-& sdot; were identified as the main contributors to BP4 degradation during UV/persulfate process.center dot The degradation pathways of BP4 during UV/persulfate process were proposed.center dot Initial persulfate concentration and solution pH both affected the yield of DBPs.center dot The higher toxic DBPs can be generated in the presence of Br- or NO3-.