Insight into carbamazepine degradation by UV/monochloramine: Reaction mechanism, oxidation products, and DBPs formation. (1st December 2018) - Bu, Lingjun
Abstract: UV/monochloramine (NH2 Cl) process has attracted some attention for the elimination of contaminants of emerging concern as a novel advanced oxidation process. However, there is still much uncertainty on the performance and mechanisms of UV/NH2 Cl process because of its complexity and generation of various species of radicals, including NH2, HO, Cl and other reactive chlorine species (RCS). The mechanism and influence factors of degradation of carbamazepine (CBZ) in the UV/NH2 Cl process were investigated, and a synergistic effect was observed. Degradation of CBZ under all investigated conditions followed pseudo-first order kinetics. The corresponding rate constant increased along with the dosage of NH2 Cl, and was affected significantly by the presence of bicarbonate and natural organic matter. The process has little pH-dependency, while the specific contribution of RCS and HO changed with solution pH, and RCS always act as a major contributor to the degradation of CBZ. Eleven byproducts of CBZ were identified and their respective evolution profiles were determined. The participation of UV in chloramination can reduce the formation of nitrogenous DBPs, but promote the formation of carbonaceous DBPs. Furthermore, when influent, sand filtered, and granular activated carbon filtered water was respectively used as background, degradation of CBZ was inhibited to different degree and more disinfection byproducts (DBPs) were generated, compared to deionized water. The electrical energy per order for degradation of CBZ in the UV/NH2 Cl process was also calculated to obtain some preliminary cost information. Graphical abstract: Highlights: UV irradiation shows synergistic effect with NH2 Cl for CBZ degradation. RCS plays a more important role than UV, HO. and NH2 in the UV/NH2 Cl process. Eleven products were identified from UV/NH2 Cl treatment of CBZ. Participation of UV inhibits formation of N-DBPs, but enhances formation of C-DBPs. UV/NH2 Cl performs well on degradation of CBZ in GAC filtered water.