Kinetic modeling and energy efficiency of UV/H2O2 treatment of iodinated trihalomethanes. (15th May 2015)

• Record Type: Journal Article
• Authors: Xiao, Yongjun; Zhang, Lifeng; Yue, Junqi; Webster, Richard D.; Lim, Teik-Thye
• Is Part Of: Water research. Volume 75(2015)
• Page Start: 259
• Page End: 269
• Publication Date: 2015-05-15
• Subjects: Iodinated disinfection by-product -- Indirect photolysis -- Matrix species -- Scavenging effect -- Steady-state kinetic model -- Electrical energy per order; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2015.02.044
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Photodegradation of I-THMs including CHCl2 I and CHI3 by the UV/H2 O2 system was investigated in this study. CHCl2 I and CHI3 react rapidly with hydroxyl radical (OH) produced by the UV/H2 O2 system, with second-order rate constants of 8.0 × 10 9 and 8.9 × 10 9 M −1 s −1, respectively. A fraction of CHCl2 I could be completely mineralized within 15 min and the remaining fraction was mainly converted to formic acid (HCO2 H). Cl − and I − were identified as the predominant end-products. No ClO3 − was observed during the photodegradation process, while IO3 − was detected but at less than 2% of the total liberated iodine species at the end of the reaction. The effects of pH, H2 O2 dose, and matrix species such as humic acid (HA), HCO3 −, SO4 2−, Cl −, NO3 − on the photodegradation kinetics were evaluated. The steady-state kinetic model has been proven to successfully predict the destruction of CHCl2 I and CHI3 by UV/H2 O2 in different water matrices. On this basis, the kinetic model combined with electrical energy per order (EE/O) concept was applied to evaluate the efficiency of the photodegradation process and to optimize the H2 O2 dose for different scenarios. The optimal H2 O2 doses in deionized (DI) water, model natural water, and surface water are estimated at 5, 12, and 16 mg L −1, respectively, which correspond to the lowest total energy consumption (EE/Ototal ) of 0.2, 0.31, and 0.45 kWhm −3 order −1 . Graphical abstract: Highlights: Photodegradation of CHCl2 I and CHI3 by UV/H2 O2 was investigated in this study. CHCl2 I and CHI3 can be degraded with UV/H2 O2 at a rate constant of ∼10 10 M −1 s −1 . The effect of pH, H2 O2 dose, and matrix species on photodegradation kinetics was evaluated. A kinetic model was established to predict I-THMs destruction by UV/H2 O2 in different water matrices. Figure-of-merit is analyzed to evaluate the optimum operating condition for UV/H2 O2 system.