Visible-light-induced activation of peroxymonosulfate by TiO2 nano-tubes arrays for enhanced degradation of bisphenol A

TiO2 photocatalysis and peroxymonosulfate (PMS) oxidation can exhibit a good performance in ultraviolet light but a less activity in visible light (VL). Herein, the TiO2 nano-tubes arrays (TiO2NTAs) and PMS were combined to degrade bisphenol A (BPA) under VL irradiation. Surprisingly, about 94.6% of BPA was removed in TiO2 NTAs/PMS/VL system within 30 min, which was much higher than that of TiO2 NTAs/VL (20.1%) and PMS/VL (9.4%) systems. A series of spectroscopic characterizations and photoelectrochemical measurements confirmed the formation of PMS-TiO2 complex with VL response, which can be excited by VL to transfer electrons to the conduction band (CB) of TiO2 for activating PMS. The quenching tests and electron spin resonance (ESR) spectra indicated that SO4 center dot- and center dot OH were responsible for BPA degradation, and then the possible degradation pathways of BPA were proposed. Humic acid (HA) and chloride ions (Cl-) significantly enhanced the BPA degradation, while bicarbonate (HCO3-) and phosphate (H2PO4-) exhibited an inhibition effect. Moreover, TiO2 NTAs/PMS/VL system displayed an enhanced BPA degradation in tap water and drinking water compared with deionized water, and as an immobilization catalyst which fabricated on Ti plate, TiO2 NTAs exhibited excellent stability and separability without complex catalyst separation/recovery processes. We believe this work will provide a new insight of the VL-induced photocatalytic PMS activation in practical water treatment.