Degradation of sulfamethazine in UV/monochloramine process: Kinetics, by-products formation, and toxicity evaluation

Removal of 26 corticosteroids, potential COVID-19 remedies, at environmentally relevant concentrations in water using UV/free chlorine, UV/monochloramine, and UV/hydrogen peroxide

“…The combination of NH 2 Cl with UV promotes the generation of ˙Cl, NH 2 ˙and RNS, such as NO 2 ȧnd NO˙, which can react with CSs due to their elevated oxidative potential. 28 The results indicate that combined UV/ NH 2 Cl treatment can be an effective technology for promoting CS removal, especially for UV insensitive ones such as ALD, BDP, COR, CTC, FLA and HCT. Environmental Science: Water Research & Technology Paper observed by UV/Cl 2 than by UV/NH 2 Cl (Fig.…”

“…Besides free chlorine, monochloramine is also commonly used in water treatment. 28 During the UV/ NH 2 Cl process, ˙Cl, amidogen radicals (NH 2 ˙), and reactive nitrogen species (RNS, such as nitrogen dioxide radicals (NO 2 ˙) and nitrogen oxide radicals (NO˙)) can be generated as shown in eqn ( 8)- (10). 29 As few studies investigated the removal of CSs using RCS and RNS, the efficiency of UV/NH 2 -Cl on CS removal needs further exploration.…”

Misconceptions about the chemistry of aqueous chlorine atoms and HClOH˙(aq), and a revised mechanism for the photochemical peroxydisulfate/chloride reaction

“…Two examples of published illegal loops involving HClOH˙ are discussed below. A total of 18 such illegal loops have been published, 10,18,20,21,23,26,27,30–33,35,39,40,46–118 and these are described in the ESI †…”

“…In addition to the 24 publications previously identified as having illegal Loop 7 (“E”), it also appears in 26 newly identified publications. 23,30,32,35,40,68,70,81,82,85,89,90,92,96,99–104,108–113,117,119 The rate constants in Xiang et al 2022 require a value of 5.7 × 10 11 M −1 s −1 for the reverse of the first step. 117 Simulations of Loop 7 (“E”) at pH 3 with 1 mM Cl − and 1 μM show that the steady-state concentration of HClOH˙ changes from 9.8 × 10 −14 M to 2.6 × 10 −10 M when the reverse rate constant of the first step is increased from zero to its required value.…”

“…23,30,32,35,40,68,70,81,82,85,89,90,92,96,99–104,108–113,117,119 The rate constants in Xiang et al 2022 require a value of 5.7 × 10 11 M −1 s −1 for the reverse of the first step. 117 Simulations of Loop 7 (“E”) at pH 3 with 1 mM Cl − and 1 μM show that the steady-state concentration of HClOH˙ changes from 9.8 × 10 −14 M to 2.6 × 10 −10 M when the reverse rate constant of the first step is increased from zero to its required value. This example thus shows that correcting an illegal loop can have large consequences.…”