Predominance role of the superoxide radical over the hydroxyl radical in the dechlorination of trichloroethene in aqueous phase using Cu doped TiO2

Trichloroethylene (TCE), a frequently used chlorinated solvent has been completely degraded in aqueous solution over the as-synthesised Cu-TiO2 irradiated with UV light. The effect of pH and the role played by specific generated reactive oxygen species in the mineralisation process were evaluated. Cu-TiO2 was synthesised and characterised according to our previous study. The photodegradation results, which followed the pseudo-first-order kinetic model, revealed that pH had a negligible effect on the degradation as the complete dechlorination occurred in all adjusted pH solutions. In addition, probe compound tests using nitrobenzene and tetrachloromethane suggested that the hydroxyl radical (OH) is mainly generated when coupling UV with Cu-TiO2, and the superoxide radical anion (O2•−) is highly generated when UV is applied alone. Free radical quenching studies demonstrated that O2•− is the major radical responsible for the degradation of TCE compared to OH. The results obtained in the present study can serve as a support for further studies on the removal of TCE using UV coupling catalyst.