Reaction of Chlorine Dioxide with Saturated Nitrogen-Containing Heterocycles and Comparison with the Micropollutant Behavior in a Real Water Matrix

Abstract

Chlorine dioxide (ClO2) is a very selective oxidant that reacts with electron-rich moieties such as activated amines and thus can degrade specific N-containing micropollutants. N-containing heterocycles (NCHs) are among the most frequent moieties of pharmaceuticals. In this study, the reactions of ClO2 with ritalinic acid and cetirizine, two abundant micropollutants, and model compounds representing their NCH moiety were investigated. The pH-dependent apparent reaction rates of all NCHs with ClO2 were measured and modeled. This model showed that neutral amines are the most important species having reaction rates between 800 and 3200 M–1 s–1, while cationic amines are not reactive. Ritalinic acid, cetirizine, and their representative model compounds showed a high stoichiometric ratio of ≈5 moles ClO2 consumption per degraded ritalinic acid and ≈4 moles ClO2 consumption per degraded cetirizine, respectively. Investigation of chlorine-containing byproducts of ClO2 showed that all investigated NCHs mostly react by electron transfer and form above 80% chlorite. The reactions of the model compounds were well comparable with cetirizine and ritalinic acid, indicating that the model compounds indeed represented the reaction centers of cetirizine and ritalinic acid. Using the calculated apparent reaction rate constants, micropollutant degradation during ClO2 treatment of surface water was predicted for ritalinic acid and cetirizine with −8 to −15% and 13 to −22% error, respectively. The results indicate that in ClO2-based treatment, piperidine-containing micropollutants such as ritalinic acid can be considered not degradable, while piperazine-containing compounds such as cetirizine can be moderately degraded. This shows that NCH model compounds could be used to predict micropollutant degradation.

Reaction of methionine with chlorine: kinetics, product formation, and potential use as a scavenger in chlorine dioxide-based systems

“…Hydroquinone is reported to form 100% ClO 2 − . 6,8,21 DMP is also reported to form 100% ClO 2 − ; 9 however, the reactive moiety of DMP is a tertiary amine. This compound is investigated as well to discover if different functional groups have different outcomes in the chlorine balances.…”

“…While phenol is reported to show 50% FAC and 50% ClO 2 − formation, 4,5 1,4-dimethylpiperazine (DMP) and hydroquinone have been observed to form 100% ClO 2 − in ClO 2 -based reactions as inorganic by-products. 6,9 GSH was investigated as a sulfur-containing model compound.…”

“…While phenol is reported to form 50% FAC and 50% ClO 2 − , 4,5 hydroquinone and DMP are reported to form 100% chlorite. 6,8,9,21,22 These data will later be compared to the chlorine balances measured with the methionine method.…”

“…4 Glycine has also been used as a selective scavenger. [6][7][8][9] Glycine reacts fast with FAC (k app = 1.5 × 10 5 M −1 s −1 at pH 7) 14 and slow with ClO 2 (k app = <10 −5 M −1 s −1 at pH 7) 15 and is, therefore, a suitable scavenger for intrinsically formed FAC. The reaction of FAC with glycine forms chloro-glycine (Cl-Gly), which can be detected photometrically in the presence of iodide in excess 16 or with IC simultaneous to other chlorine species formed in the reaction (glycine method).…”

Reaction Mechanisms of Chlorine Dioxide with Phenolic Compounds─Influence of Different Substituents on Stoichiometric Ratios and Intrinsic Formation of Free Available Chlorine

“…However, by discovering the formation of undesired halogenated disinfection byproducts (DBPs) in FAC application, , the usage of other oxidants such as O 3 or ClO 2 has increased. Although ClO 2 forms only small yields of halogenated DBPs compared to FAC, it forms chlorite (ClO 2 – ) and chlorate (ClO 3 – ) as major byproducts. − Recently, it was discovered that ClO 2 also forms FAC as a secondary oxidant with specific reaction partners. − …”