Comparative evaluation of iodoacids removal by UV/persulfate and UV/H2O2 processes. (1st October 2016)

• Record Type: Journal Article
• Authors: Xiao, Yongjun; Zhang, Lifeng; Zhang, Wei; Lim, Kok-Yong; Webster, Richard D.; Lim, Teik-Thye
• Is Part Of: Water research. Volume 102(2016)
• Page Start: 629
• Page End: 639
• Publication Date: 2016-10-01
• Subjects: Iodinated disinfection by-product -- UV/PS -- UV/H2O2 -- Sulfate radical -- Hydroxyl radical -- QSAR model; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2016.07.004
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: To develop a cost-effective method for post-formation mitigation of iodinated disinfection by-products, degradation of iodoacids by UV, UV/PS (persulfate), and UV/H2 O2 was extensively investigated in this study. UV direct photolysis of 4 iodoacids followed first-order kinetics with rate constants in the range of 2.43 × 10 −4 −3.02 × 10 −3 cm 2 kJ −1 . The derived quantum yields (Ф254 ) of the 4 iodoacids range from 0.13 to 0.34, respectively. A quantitative structure-activity relationship (QSAR) model was subsequently established and applied to predict the direct photolysis rates of 6 other structurally similar iodoacids whose standards are commercially unavailable. At a UV dose of 140 mJ cm −2 which is typically applied for disinfection of drinking water, the removal percentages of 4 iodoacids were only between 3.35% and 34.7%. Thus, ICH2 CO2 H (IAA), the most photo-recalcitrant species, was selected as the target compound for removal in the UV/PS and UV/H2 O2 processes. The IAA degradation rates decreased with increasing pH from 3 to 11 in both processes. Humic acid (HA) and HCO 3 − had inhibitory effects on IAA degradation in both processes. Cl − adversely affected the IAA degradation in the UV/PS process but had no effect in the UV/H2 O2 process. Generally, in the deionized (DI) water, surface water, treated drinking water, and secondary effluent, UV/PS process is more effective than UV/H2 O2 process for IAA removal, based on the same molar ratio of oxidant: IAA. SO4 − generated in the UV/PS process yields a greater mineralization of IAA than HO in the UV/H2 O2 process. IO 3 − was the predominant end-product in the UV/PS process, while I − was the major end-product in the UV/H2 O2 process. The respective contributions of UV, HO, and SO4 − for IAA removal in the UV/PS process were 7.8%, 14.7%, and 77.5%, respectively, at a specific condition (1.5 μM IAA, 60 μM oxidant, and pH 7). Compared to UV/H2 O2 process, UV/PS was also observed as more cost-effective process based on the electrical energy per order (EE/O) and chemical cost. Graphical abstract: Highlights: Photodegradation of iodoacids by UV, UV/persulfate, and UV/H2 O2 was investigated. A quantitative structure-activity relationship model was established for direct photolysis. UV/PS and UV/H2 O2 were compared for operational efficiency and degradation products. The respective contributions of UV, HO, and SO4 − for IAA removal were determined. Economic comparison of AOP systems was based on energy and oxidant consumption.