Kinetics of diatrizoate degradation by ozone and the formation of disinfection by-products in the sequential chlorination

Abstract

In this study, we studied the degradation kinetics of a common iodine contrast agent, diatrizoate, by ozone and the formation of disinfection by-products (DBPs) in the sequential chlorination. Effects of ozone concentration, solution pH, and bromide concentration on diatrizoate degradation were evaluated. The results indicate that diatrizoate can be effectively degraded (over 80% within 1 h) by ozone, and the degradation kinetics can be well described using the pseudo-first-order kinetic model. The pseudo-first-order rate constant (kobs) of diatrizoate degradation significantly increased with increasing ozone concentration and decreasing bromide concentration. The kobs kept increasing with the increase of pH value and reached a maximum of 6.5 (±0.05) × 10−2 min−1 at pH 9. As the ozone concentration gradually increased from 0.342 to 1.316 mg/L, the corresponding kobs of diatrizoate degradation increased from 1.76 (±0.20) × 10−3 to 4.22 (±0.3) × 10−2 min−1. The bromide concentration exhibited a strong inhibitory effect on diatrizoate degradation because of the competition for ozone with diatrizoate. Trichloromethane was the only detected DBP in the subsequent chlorination in the absence of bromide. However, in the presence of bromide, six other DBPs were detected, and bromochloroiodomethane and tribromomethane became the major products with concentrations 1–2 orders higher than those of the other DBPs. In order to provide safe drinking water to the public, water should be maintained at circumneutral pH values and low bromine concentrations (<5 μM) before reaching the chlorine disinfection process to effectively control the formation of DBPs.

Trichloramine and Hydroxyl Radical Contributions to Dichloroacetonitrile Formation Following Breakpoint Chlorination

“…Meanwhile, tracking NOM changes by using high-resolution mass spectrometry is suggested to improve the understanding of the generation of N-DBP precursors at molecular levels . Additionally, bromide is commonly present in natural waters, and its presence is known to promote the formation of brominated DBPs (Table S9), which are associated with high health risks compared to their chlorinated analogs. , The research on the formation of bromine-substituted acetonitriles from breakpoint chlorination is desired.…”

“…53 Additionally, bromide is commonly present in natural waters, and its presence is known to promote the formation of brominated DBPs (Table S9), which are associated with high health risks compared to their chlorinated analogs. 4,54 The research on the formation of bromine-substituted acetonitriles from breakpoint chlorination is desired.…”

Overlooked Cytotoxicity and Genotoxicity to Mammalian Cells Caused by the Oxidant Peroxymonosulfate during Wastewater Treatment Compared with the Sulfate Radical-Based Ultraviolet/Peroxymonosulfate Process

“…HOCl and HOBr are requisite intermediates for chlorate and bromate formation. However, the hypohalous acids also undergo electrophilic substitution or electrophilic addition to form organic halogen in the presence of dissolved organic matter (DOM) in wastewater. − There was an approximately 20% electrophilic substitution rate at pH 7 when HOBr reacts with Suwannee River natural organic matter (NOM), humic acid, fulvic acid, and Nordic reservoir NOM, suggesting that much organic halogen would form. Therefore, many individual halogenated byproducts like trihalomethanes (THMs), haloacetic acid (HAAs), haloacetonitriles (HANs), halonitromethanes (HNMs), and haloacetamides (HAcAms), as well as a considerable amount of total organic halogen (TOX), have been found in SO 4 •– -based oxidation processes. , …”

Editorial: Water recycling and low-carbon development

“…Yin et al (2021) study the removal efficiencies and mechanism of atrazine degradation by peroxymonosulfate activated with CuCo 2 O 4 nano-particles. Hu et al (2021) present a study on diatrizoate degradation by ozone and the formation of disinfection byproducts in the sequential chlorination. Yi et al (2021) investigate the effect of commercial probiotics immobilized by various carriers on the remediation of aquaculture water and sediment.…”