Insights into the wavelength-dependent photolysis of chlorite: Elimination of carbamazepine and formation of chlorate

Simultaneous removal of chlorite (ClO2- ) and organic micro-pollutants (OMPs) by the irradiation of UV is a novel process. In this study we used UV light emitting diode (UV-LED) as a new UV source to systematically investigate the effect of UV wavelength (255, 285, 365 nm) on the simultaneous removal of carbamazepine (CBZ) and ClO2- . Removal of both CBZ and ClO2- followed the order of 255, 285, and 365 nm. Formation of hydroxyl radical and reactive chlorine species (RCS) were confirmed during the photolysis of ClO2- using probe compounds. RCS were always the predominant contributor to the degradation of CBZ in UV-LED/ClO2- system. The impacts of ClO2- dosage, pH, bicarbonate/carbonate (HCO3-/CO32- ), and the effect of natural organic matter (NOM) on CBZ degradation were also evaluated. This study identified the products produced by CBZ through possible degradation pathways during the transformation process. Further, the amount of ClO2- may affect the amount of chlorate produced in UV/ClO2- system. Overall, our research provides an in-depth analysis of the effects of UV wavelength on the simultaneous removal of ClO2- and OMPs in water.