Anodic oxidation of isothiazolin-3-ones in aqueous medium by using boron-doped diamond electrode

Electrochemical degradation of biocide compound, isothiazolin-3-ones, was studied in aqueous medium, with Na2SO4 supporting electrolyte using boron-doped diamond (BDD) anode. The redox response of isothiazolin-3-ones at BDD was examined by cyclic voltammetric study. The degradation of isothiazolin-3-ones and its mineralization trend were monitored by UV-vis spectrophotometric method and total organic carbon (TQC) analyzer, respectively. The effect of operating parameters such as applied current density, biocide concentration, electrolyte pH and nature of supporting electrolytes (Na2SO4, NaNO3 and NaCl) on degradation rate was studied in detail. It was established that the hydroxyl radicals (center dot OH) generated at BDD surface were responsible for the degradation and the mineralization of the biocide contaminant. The rate of degradation was almost independent of electrolyte pH but became faster as the applied current density increased and the biocide concentration decreased. The kinetic studies revealed that the biocide decay follows a pseudo-first-order rate. The apparent rate constant for the oxidation of isothiazolin-3-ones was determined to be 2.65 x 10(-4)s(-1) at an applied current density of 25 mA cm(-2) in the presence of 0.1 mol dm(-3) Na2SO4 at pH 6.0. A poor mineralization efficiency was observed in the case of NaCl as supporting electrolyte which cause in-situ generation of chlorine based mediated oxidants such as Cl-2 and OCl- which have negligible influence in mineralizing the isothiazolin-3-ones compared to peroxodisulfate (S2O82-) oxidants that formed in the case of Na2SO4. The oxidizing ability of the BDD anode was compared with those of Pt and glassy carbon anodes under similar experimental conditions. (C) 2016 Elsevier B.V. All rights reserved.