Kinetics for diclofenac degradation by chlorine dioxide in aqueous media: Influences of natural organic matter additives

摘要

The kinetics involved with the oxidation of diclofenac (DCF) by chlorine dioxide was investigated in the absence, and presence, of natural organic matter additives. Under the study conditions, we demonstrated that DCF may be rapidly and completely oxidized by excess ClO2. The observed pseudo first-order rate constant (k(obs)) increased linearly with ClO2 concentration. Addition of cationic (CTAB), anionic (SDBS), and non-ionic (Tween-80) surfactants as additives conveyed significant influences on the kinetic properties of the DCF-ClO2 reaction. Primarily, surface promotion was observed in low concentrations of CTAB through the adsorption of the reacting species on micellar surfaces, as both reactants were ionic, while this rate enhancement was suppressed in high concentrations of CTAB. Instead, inhibitory effects were observed on the samples that had been added SDBS, Tween-80 or humic acid with it being most effective, which confirmed the environmental relevance of the observed interactions between DCF and natural organic constituents.

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