Comparison of UV-induced AOPs (UV/Cl2, UV/NH2Cl, UV/ClO2 and UV/H2O2 ) in the degradation of iopamidol: Kinetics, energy requirements and DBPs-related toxicity in sequential disinfection processes

Fu-Xiang Tian; Wen-Kai Ye; Bin Xu; Xiao-Jun Hu; Shi-Xu Ma; Fan Lai; Yu-Qiong Gao; Hai-Bo Xing; Wei-Hong Xia; Bo Wang

doi:10.1016/j.cej.2020.125570

Comparison of UV-induced AOPs (UV/Cl₂, UV/NH₂Cl, UV/ClO₂ and UV/H₂O₂ ) in the degradation of iopamidol: Kinetics, energy requirements and DBPs-related toxicity in sequential disinfection processes

Chem Eng J. 2020 Oct 15:398:125570. doi: 10.1016/j.cej.2020.125570. Epub 2020 May 30.

Authors

Fu-Xiang Tian¹, Wen-Kai Ye¹, Bin Xu², Xiao-Jun Hu¹, Shi-Xu Ma¹, Fan Lai¹, Yu-Qiong Gao³, Hai-Bo Xing¹, Wei-Hong Xia¹, Bo Wang¹

Affiliations

¹ School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai 201418, PR China.
² State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
³ School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093, PR China.

Abstract

The UV-induced advanced oxidation processes (AOPs, including UV/Cl₂, UV/NH₂Cl, UV/ClO₂ and UV/H₂O₂ ) degradation kinetics and energy requirements of iopamidol as well as DBPs-related toxicity in sequential disinfection were compared in this study. The photodegradation of iopamidol in these processes can be well described by pseudo-first-order model and the removal efficiency ranked in descending order of UV/Cl₂ > UV/H₂O₂ > UV/NH₂Cl > UV/ClO₂ > UV. The synergistic effects could be attributed to diverse radical species generated in each system. Influencing factors of oxidant dosage, UV intensity, solution pH and water matrixes (Cl^- , NH₄ ⁺ and nature organic matter) were evaluated in detail. Higher oxidant dosages and greater UV intensities led to bigger pseudo-first-order rate constants (K_obs) in these processes, but the pH behaviors exhibited quite differently. The presence of Cl^- , NH₄ ⁺ and nature organic matter posed different effects on the degradation rate. The parameter of electrical energy per order (EE/O) was adopted to evaluate the energy requirements of the tested systems and it followed the trend of UV/ClO₂ > UV > UV/NH₂Cl > UV/H₂O₂ > UV/Cl₂ . Pretreatment of iopamidol by UV/Cl₂ and UV/NH₂Cl clearly enhanced the production of classical disinfection by-products (DBPs) and iodo-trihalomethanes (I-THMs) during subsequent oxidation while UV/ClO₂ and UV/H₂O₂ exhibited almost elimination effect. From the perspective of weighted water toxicity, the risk ranking was UV/NH₂Cl > UV/Cl₂ > UV > UV/H₂O₂ > UV/ClO₂ . Among the discussed UV-driven AOPs, UV/Cl₂ was proved to be the most cost-effective one for iopamidol removal while UV/ClO₂ displayed overwhelming advantages in regulating the water toxicity associated with DBPs, especially I-THMs. The present results could provide some insights into the application of UV-activated AOPs technologies in tradeoffs between cost-effectiveness assessment and DBPs-related toxicity control of the disinfected waters containing iopamidol.

Keywords: Degradation; Electrical energy per order (EE/O); Iodo-trihalomethanes (I-THMs); Iopamidol; Toxicity; UV-based advanced oxidation processes (AOPs).