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Chlorine dioxide (ClO

This study systematically investigated the reactions of N-acetyl-l-tyrosine (NAL-tyrosine) and N-acetyl-l-tryptophan (NAL-tryptophan) as examples for reactive moieties of microbial membrane proteins with ClO2 and FAC.

Chlorine dioxide (ClO2) is used for disinfection of water and pollutant control. Recently it was shown that free available chlorine (FAC) is formed during the oxidation of organic compounds with ClO2. To investigate the moieties in natural organic matter (NOM) responsible for the FAC formation, reactions of ClO2 with phenols and olefins were investigated. Thereby primary yields of the inorganic by-products chlorite, chloride, FAC, and chlorate were determined and compared with Suwannee River natural organic matter (SRNOM). The reaction of ClO2 with the studied model compounds (vanillin, hydroquinone, indigotrisulfonate, and dimedone) revealed very different inorganic by-products. The main inorganic by-product of all investigated compounds was chlorite (>50% per consumed ClO2). Besides chlorite, vanillin formed 35% chloride and 4% chlorate, indigotrisulfonate 25% chloride, 7% FAC and 3% chlorate and dimedone 50% chloride and 4% chlorate. Hydroquinone formed exclusively chlorite (90%). Yields of FAC formed by ClO2 oxidation of SRNOM were significant (22%), which principally could result in halogenated organic by-products. Additionally, chlorite (63%), chloride (8%) and chlorate (5%) were formed. The yield of FAC decreased significantly after pre-ozonation, which can be explained by ozone induced formation of poly-hydroxylated aromatic compounds, which may mainly form chlorite in analogy to hydroquinone.

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.

Chlorine dioxide (ClO2) has been used as a disinfectant in water treatment for a long time, and its use for micropollutant abatement in wastewater has recently been suggested. Surprisingly, a mechanistic understanding of ClO2 reactions in (waste)water matrices is largely lacking. The present study contributes to this mechanistic understanding by performing a detailed investigation of ClO2 reactions with organic matter using phenol as a surrogate for reactive phenolic moieties. A concept for indirectly determining HOCl using 2- and 4-bromophenol was developed. The reaction of phenol with ClO2 formed chlorite (62 ± 4% per ClO2 consumed) and hypochlorous acid (HOCl) (42 ± 3% per ClO2 consumed). The addition of ClO2 to wastewater (5 × 10–5 M ClO2) resulted in 40% atenolol and 47% metoprolol transformation. The presence of the selective HOCl scavenger glycine largely diminished their transformation, indicating that atenolol and metoprolol were transformed by a fast reaction with HOCl (e.g., k (atenolol + HOCl)...