New Book Chapter

Chlorine dioxide (ClO₂) is used in water treatment for disinfection, pre-oxidation, and recently pollutant degradation. However, there are significant gaps in the knowledge of byproduct formation in ClO₂ applications. The mechanisms by which organic compounds react with ClO₂ differ vastly with the slightest change in the reaction centre and its adjacent reactive moieties (e.g. phenol, hydroquinone, vanillin). This leads to the formation of various inorganic byproducts such as chlorite, chloride, and free chlorine as a secondary oxidant. Chlorite and chlorate are regulated, and free chlorine can further contribute to the formation of halogenated byproducts. The current chapter provides an overview of the current knowledge for the mechanisms of ClO₂ oxidation and byproduct formation. The reactive moieties of organic compounds towards ClO₂ will be discussed, and a compilation of their reaction rates will be presented. Moreover, the pathways that might form free chlorine and the benefit of its formation to the degradation of recalcitrant pollutants towards ClO₂ are discussed. This chapter also covers how inorganic byproduct formation will differ based on the reaction partner and how they interact with each other. In the end, measures of byproducts reduction involving ClO₂ will be discussed.

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