Synergistic effects of ozone/peroxymonosulfate for isothiazolinone biocides degradation: Kinetics, synergistic performance and influencing factors. (1st February 2022) - Yang, Zheng-Wei
Abstract: Synergistic effects of ozone (O3 ) and peroxymonosulfate (PMS, HSO5 − ) for isothiazolinone biocides degradation was studied. The synergistic ozonation process (O3 /PMS) increased the efficiency of methyl-isothiazolinone (MIT) and chloro-methyl-isothiazolinone (CMIT) degradation to 91.0% and 81.8%, respectively, within 90 s at pH 7.0. This is 30.6% and 62.5% higher than the corresponding ozonation efficiency, respectively. Total radical formation value ( R ct, R ) for the O3 /PMS process was 24.6 times that of ozonation alone. Calculated second-order rate constants for the reactions between isothiazolinone biocides and ( k SO4 -, MIT and k SO4 -, CMIT ) were 8.15 × 10 9 and 4.49 × 10 9 M −1 s −1, respectively. Relative contributions of O3, hydroxyl radical (OH) and oxidation to MIT and CMIT removal were estimated, which were 15%, 45%, and 40% for O3, OH and oxidation to MIT, and 1%, 67%, and 32% for O3, OH and oxidation to CMIT at pH 7.0, respectively. Factors influencing the O3 /PMS process, namely the solution pH, chloride ions (Cl − ), and bicarbonate (HCO3 − ), were evaluated. Increasing the solution pH markedly accelerated O3 decay and OH and formation, thus weakening the relative contribution of O3 oxidation while enhancing that of OH and . Cl − had a negligible effect on MIT and CMIT degradation. Under the dual effect of bicarbonate (HCO3 − ) as inhibitor and promoter, low concentrations (1–2 mM) of bicarbonate weakly promoted MIT and CMIT degradation, while high concentrations (10–20 mM) induced strong inhibition. Lastly, oxidation performance of O3 and O3 /PMS processes for MIT and CMIT degradation in different water matrices was compared. Graphical abstract: Image 1 Highlights: The O3 /PMS process showed synergistic effects for MIT and CMIT degradation. Radical formation and oxidation in the O3 /PMS process were evaluated. k SO4 .-, MIT and k SO4-, CMIT were determined via the secondary reaction kinetics The influencing factors of the O3 /PMS process were systematically evaluated. The oxidation performance of O3 /PMS in different water matrices was compared.