Iodinated trihalomethanes formation in iopamidol-contained water during ferrate/chlor(am)ination treatment. (June 2021)

• Record Type: Journal Article
• Authors: Li, Mian; Zhang, Tian-Yang; Xu, Bin; Hu, Chen-Yan; Dong, Zheng-Yu; Wang, Zhen; Tang, Yu-Lin; Yu, Shui-Li; Pan, Yang; Xian, Qiming
• Is Part Of: Chemosphere. Volume 272(2021)
• Publication Date: 2021-06
• Subjects: Ferrate (Fe(VI)) -- Iopamidol -- Chlorination -- Chloramination -- Iodinated trihalomethanes (I-THMs); Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2021.129568
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Iopamidol is a commonly used iodinated X-ray contrast media in medical field, and its residue in water can react with disinfectants to form highly toxic iodinated disinfection by-products (I-DBPs). This study investigated the degradation of iopamidol and formation of DBPs, especially iodinated trihalomethanes (I-THMs), during ferrate (Fe(VI)) pre-oxidation and subsequent chlor(am)ination under raw water background. It was found that iopamidol degradation efficiency in raw water by Fe(VI) at pH 9 could reach about 80%, which was much higher than that at pH 5 and pH 7 (both about 25%). With Fe(VI) dose increasing, iopamidol removal efficiency increased obviously. During the iopamidol degradation by Fe(VI), IO3 − was the dominant product among all the iodine species. After pre-treated by Fe(VI), yields of THM4 and I-THMs can be reduced in subsequent chlor(am)ination. Besides, pH was a crucial factor for Fe(VI) pre-oxidition controlling DBPs. With the pH increasing from 5 to 9, the yield of THM4 kept increasing in subsequent chlorination but showed the highest amount at pH 6 in subsequent chloramination. The yield of I-THMs increased first and then decreased with the increase of pH in both subsequent chlorination and chloramination. I-THM concentrations in chlorinated samples were lower than chloraminated ones under acidic conditions but became higher under neutral and alkaline conditions. The total CTI of THMs during Fe(VI)-chloramination was higher than that during Fe(VI)-chlorination under neutral condition, but sharply decreased under alkaline conditions. In summary, Fe(VI)-chloramination subsequent treatment under alkaline conditions should be an effective method for iopamidol removal and DBP control. Graphical abstract: Image 1 Highlights: Iopamidol removal efficiency by Fe(VI) is higher at pH > 7 than that at pH ≤ 7. IO3 − was a dominant iodine product during iopamidol degradation by Fe(VI). Fe(VI)-chloramination is effective in reducing THMs under alkaline conditions. The toxicity contribution of CHI3 is the highest in Fe(VI)-chloramination.