Refinement of kinetic model and understanding the role of dichloride radical (Cl2â¢-) in radical transformation in the UV/NH2Cl process.
Water Res
; 254: 121440, 2024 May 01.
Article
en En
| MEDLINE
| ID: mdl-38479170
ABSTRACT
The ultraviolet/monochloramine (UV/NH2Cl) process is an emerging advanced oxidation process with promising prospects in water treatment. Previous studies developed kinetic models of UV/NH2Cl for simulating radical concentrations and pollutant degradation. However, the reaction rate constants of Cl2â¢- with bicarbonate and carbonate (kCl2â¢-, HCO3- and kCl2â¢-, CO32-) were overestimated in literature. Consequently, when dosing 1 mM chloride and 1 mM bicarbonate, the current models of UV/NH2Cl severely under-predicted the experimental concentrations of three important radicals (i.e., hydroxyl radical (HOâ¢), chlorine radical (Clâ¢), and dichloride radical (Cl2â¢-)) with great deviations (> 90 %). To investigate this issue, the transformation reactions among these three radicals in UV/NH2Cl were systematically studied. For the first time, it was found that in addition to Clâ¢, Cl2â¢- was also an important parent radical of HO⢠in the presence of chloride, and chloride could effectively compensate the inhibitory effect of bicarbonate on HO⢠generation in the system. Moreover, reactions and rate constants in current models were scrutinized from corresponding literature, and the reaction rate constants of Cl2â¢- with bicarbonate and carbonate (kCl2â¢-, HCO3- and kCl2â¢-, CO32-) were reevaluated to be 1.47 × 105 and 3.78 × 106 M-1s-1, respectively, by laser flash photolysis. With the newly obtained rate constants, the refined model could accurately simulate concentrations of all three radicals under different chloride and bicarbonate dosages with satisfactory deviations (< 30 %). Meanwhile, the refined model performed much better in predicting pollutant degradation and radical contribution compared with the unrefined model (with the previously estimated kCl2â¢-, HCO3- and kCl2â¢-, CO32-). The results of this study enhanced the accuracy and applicability of the kinetic model of UV/NH2Cl, and deepened the understanding of radical transformation in the process.
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Base de datos:
MEDLINE
Asunto principal:
Contaminantes Químicos del Agua
/
Purificación del Agua
Idioma:
En
Revista:
Water Res
Año:
2024
Tipo del documento:
Article
País de afiliación:
Singapur