A promising ozone-based advanced oxidation process for effective generation of hydroxyl radicals in acidic solution

The oxidative efficiency of H 2 O 2 /O 3 in the presence or absence of titanium silicalite of TS-1 was investigated at pH value of 3.0, in which acetic acid was selected as the target organic compound owing to its inert to ozone. The removal rate of acetic acid by H 2 O 2 /O 3 was negligible (5.6% in 30   min) because of the impossible deprotonation reaction of H 2 O 2 in acidic solution. However, addition of titanium silicalite of TS-1 could greatly improve the oxidative efficiency of H 2 O 2 /O 3 (29% in 30   min). The results of effects of different parameters such as concentration of H 2 O 2 , concentration of TS-1, rate of ozone input, and pH value, on the oxidative efficiency of TS-1/H 2 O 2 /O 3 showed that the degradation of HAc by TS-1/H 2 O 2 /O 3 was controlled by the transfers of reactants (including ozone and HAc) to the surface of TS-1. The tests of addition of tert-butyl alcohol and dimethyl sulfoxide (DMSO) both confirmed generation of hydroxyl radicals in this process. The rate of generation of hydroxyl radicals could be controlled by adjusting the concentration of H 2 O 2 . The mechanism for generation of hydroxyl radicals might be the reaction of some reactive oxygen species (including Ti(IV)-superoxide and Ti(IV)-hydroperoxide/peroxide), which resulted from the interaction of TS-1 with H 2 O 2 , with dissolved ozone. The results are of significance for the effective pretreatment of acidic wastewater containing refractory ozone-inert organic matter.