Abstract
The UV/NH2Cl process is an emerging advanced oxidation process (AOP) that is greatly effective in degrading pharmaceuticals and personal care products (PPCPs). However, detailed information regarding the process is lacking. The degradation of ibuprofen (IBP, an electron-withdrawing PPCP) and naproxen (NPX, an electron-donating PPCP) in UV/NH2Cl and UV/NaClO processes was performed to investigate the applicability and security of the UV/NH2Cl process and compare with those of UV/NaClO. UV/NH2Cl was effective in degrading both IBP and NPX and the degradation followed pseudo-first order kinetics (kIBP = 0.0037 cm2/mJ and kNPX = 0.0044 cm2/mJ). This indicated the broad applicability of UV/NH2Cl to different kinds of PPCPs. Ranges of values of UV intensity (0.3–1.0 mW/cm2) and pH (6.0–8.0) showed little effect on the degradation of PPCPs by UV/NH2Cl based on UV Dose but HCO3− (2–8 mM), natural organic matter (NOM, 2–8 mg/L), and the natural water matrixes were inhibitory. Increasing the dosage of NH2Cl from 0.15 mM to 0.75 mM, resulted in an even increase of kIBP; however, kNPX increased slowly after 0.3 mM NH2Cl. Mechanism experiments involving nitrobenzene showed that •OH was the major radical involved in degrading IBP and NPX via UV/NH2Cl. The electron spin resonance spectroscopy and kinetic modeling results also indicated the larger amount of •OH and weaker reactive chlorine species (mainly ClO• and ClO2•) in UV/NH2Cl compared with UV/NaClO. Compared to UV/NaClO in synthetic and natural water, UV/NH2Cl was a more stable degrader with little pH- and substrate-dependence, while UV/NaClO preferred degrading the electron-donating PPCP and at low pH. The UV/NH2Cl produced less halogenated disinfection byproducts (DBPs) (even nitrogenous DBPs) and was less cytotoxic theoretically than UV/NaClO based on the DBPs included in this study. Thus UV/NH2Cl process may be an effective AOP for water treatment.
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