Electrochemical degradation of methylisothiazolinone by using Ti/SnO2-Sb2O3/α, β-PbO2 electrode: Kinetics, energy efficiency, oxidation mechanism and degradation pathway

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 374; pp. 626 - 636
• Main Authors: Wang, Yingcai, Chen, Min, Wang, Can, Meng, Xiaoyang, Zhang, Weiqiu, Chen, Zefang, Crittenden, John
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.10.2019
• Subjects: Degradation pathway; Electrochemical oxidation; Energy efficiency; Methylisothiazolinone; Oxidation mechanism; Methylisothiazolinone; Energy efficiency; Oxidation mechanism; Electrochemical oxidation; Degradation pathway
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2019.05.217

•MIT was electrochemical degraded by a Ti/SnO2-Sb2O3/α, β-PbO2 electrode.•Electrochemical treatment required low energy consumption and no chemical addition.•68.8% of electrons that used for MIT oxidation was utilized to mineralize MIT into CO2.•The sulfur atom can be oxidized into SO42− and separated from MIT ring structure. Methylisothiazolinone (2-methyl-4-isothiazolin-3-one) (MIT) is a commonly used biocide in wastewater treatment processes. Residual MIT in wastewater leads to high environmental risks and toxicity. The degradation of MIT via electrochemical oxidation, including kinetics, energy efficiency, oxidation mechanism and degradation pathway, was investigated in this study. Findings from energy and cost evaluation by using electrochemical technology were compared with those of other technologies. Experimental results indicate that electrolyte, current density and initial concentration can significantly affect MIT degradation. The lowest electrical energy per order was less than 3.85 kWh m−3 when NaCl was used as the electrolyte. Electrochemical degradation is advantageous because it can be easily applied without adding chemicals into wastewater and has relative low costs. The oxygen evolution, production of recalcitrant byproducts, and the mass transfer limitation resulted in the decrease of instantaneous current efficiency and mineralization current efficiency. Electron efficiency analysis demonstrated that 68.8% of the electrons used for MIT oxidation were effectively utilized to mineralize MIT into CO2. The proportion of direct and indirect oxidation of MIT during electrochemical degradation was quantitatively determined as 37.7% and 62.3%, respectively. HO was the most effective species for MIT degradation. MIT degradation pathway was proposed, in which the CC bond in MIT was broken down. C3H7NOS and C3H7NO4 were detected, indicating the occurrence of ring opening reaction. Sulfur was oxidized into SO42− and cleaved from C3H7NOS.