Enhanced visible-light activation of persulfate by Ti3+ self-doped TiO2/graphene nanocomposite for the rapid and efficient degradation of micropollutants in water.

In this study, a novel TiO2-x/rGO-PS-Vis process was developed, which utilizes the TiO2-x/rGO (Ti3+ and oxygen vacancies self-doped TiO2 coupled with reduced graphene oxide) nanocomposite as a promising and efficient activator of persulfate (PS) for the enhanced oxidation of micropollutants under visible -light irradiation. TiO2-x/rGO exhibited a significantly high activity for PS activation to produce more sulfate radicals (SO4-) and hydroxyl radicals (OH). Therefore, almost 100% BPA (10 mg/L) and 80% TOC can be removed just within 12 min with 1.0 g/L TiO2-x/rGO and 2 mM PS under visible light. Moreover, it was found that many other typical micropollutants, such as phenol, acetaminophen and sulfamethoxazole can also be effectively degraded by this process. Electron paramagnetic resonance (EPR) and radical quenching experiments indicated that both SO4- and OH contribute to the degradation of organics, and the radical process was the main degradation pathway. In addition, the effects of PS concentration, catalyst dosage, initial solution pH and inorganic anions were investigated systematically. Experiments carried out in the real background of water matrix with low-concentration of BPA indicated that the proposed TiO2-x/rGO-PS-Vis process has strong non-selective photo-oxidative ability for the removal of micropollutants in water.