UV direct photolysis of halogenated disinfection byproducts: Experimental study and QSAR modeling

• Published in: Chemosphere (Oxford) 2019-11, Vol.235, p.719-725
• Main Authors: Zhang, Yiqing, Xiao, Yongjun, Zhang, Yicheng, Lim, Teik-Thye
• Format: Article
• Language: English
• Subjects: Direct photolysis; Halogenated disinfection byproduct; Multiple linear relationship; Quantitative structure-activity relationship; Rate constants; Validation
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2019.06.167

UV direct photolysis has been used as a promising process to remove halogenated disinfection byproducts (DBPs) generated in water. In this study, experimental studies and modeling approaches were applied to investigate the UV direct photolysis rate constants for 40 kinds of halogenated DBPs. The fluence-based pseudo-first-order rate constants for the removal of halogenated DBPs under UV photolysis spanned more than 2 orders of magnitude, with a range of (0.23–29.84) × 10−4 cm2 mJ−1. DBPs with higher number of halogenated substituents featured higher photolysis rate constants. The degradation efficiencies of DBPs were also affected by the species of halogen substituents, which followed the trend of iodo- > bromo- > chloro- DBPs. A quantitative structure-activity relationship (QSAR) model was established on the basis of the observed degradation rate constant values, which contained a quantum-chemical descriptor (ELUMO–EHOMO) and a molecular descriptor (Eta_C). The calculated parameters of the developed model indicated its good robustness and high reliability. The developed QSAR model can predict the degradation rate constants for DBPs within factors of 1/3 to 3. The model was validated using application domain and visualized in a Williams plot. The selected descriptors for QSAR model can explain the reaction mechanism for UV direct photolysis. •UV photolysis of 40 halogenated DBPs was investigated.•MLR method was used to develop QSPR model.•The model can predict the photodegradation rate constants of DBPs.•The model was validated using application domain and visualized in a Williams plot.•The selected descriptors gave information on the mechanism of UV photolysis.