Removal of 2-Methyl-4-Isothiazolin-3-One by VUV/UV/Persulfate for Sustainable Wastewater Reclamation: Effects of Inorganic Anions on the Concentrations and Contributions of Hydroxyl Radicals and Sulfate Radicals

Yi-Fan Zhang, Hong-Wei Xu and Nan Huang ()
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Yi-Fan Zhang: National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, College of Environmental Science and Engineering, Beijing University of Technology, Beijing 100124, China
Hong-Wei Xu: Environmental Simulation and Pollution Control State Key Joint Laboratory, State Environmental Protection Key Laboratory of Microorganism Application and Risk Control (SMARC), School of Environment, Tsinghua University, Beijing 100084, China
Nan Huang: National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, College of Environmental Science and Engineering, Beijing University of Technology, Beijing 100124, China

Sustainability, 2025, vol. 17, issue 21, 1-14

Abstract: The non-oxidizing antimicrobial 2-Methyl-4-Isothiazolin-3-one (MIT) poses a significant environmental risk given its frequent detection in municipal wastewater. This study showed that the combination of Vacuum UV/UV (VUV/UV) and persulfate (PDS) efficiently achieved the rapid transformation and removal of 10 μM MIT within 90 s, which is much faster than UV, UV/PDS, and VUV/UV. Increasing the PDS dosage improved MIT degradation, whereas changes in pH between 4 and 10 had little effect. Radical quenching experiments showed that 93% of the MIT oxidation was attributable to the hydroxyl radical (•OH) and the sulfate radical (SO 4 • − ). SO 4 • − and •OH at concentrations of 8.6 × 10 −12 M and 1.5 × 10 −12 M accounted for 32% and 61% of the MIT degradation, respectively, and the greater contribution of •OH was attributed to its higher reaction rate constant with MIT compared to SO 4 • − . Sulfate had a negligible impact on the radical concentrations. Chloride (1 mM) reduced the SO 4 • − and •OH concentrations by 61% and 27%, respectively. And the SO 4 • − contribution to MIT degradation fell to 19%. Nitrate (5 mM) readily quenched •OH but minimally affected SO 4 • − . The •OH concentration decreased by 79%, reducing its contribution to 27%. Bicarbonate/carbonate (5 mM) simultaneously reduced the SO 4 • − and •OH by 26–30% and had little effect on their contributions. Because of the quenching effect of organic matter and inorganic anions on radicals, secondary effluent inhibited the degradation of MIT. After a 120 s treatment, the total organic carbon, UV 254 , and fluorescence regional integration were reduced by 5%, 8%, and 17–24%, respectively. This study provides a quantitative analysis of how inorganic ions alter the concentrations and contributions of •OH and SO 4 • − , elucidating the MIT removal mechanisms in VUV/UV/PDS for sustainable wastewater reclamation.

Keywords: VUV/UV/persulfate; 2-methyl-4-Isothiazolin-3-one; hydroxyl and sulfate radicals; inorganic anions; sustainable wastewater reclamation (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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