ISSN 1203-8407 © 2016 Science & Technology Network, Inc. J. Adv. Oxid. Technol. Vol. 19, No. 2, 2016 338 Removal of Benzothiazole from Contaminated Waters by Ozonation: The Role of Direct and Indirect Ozone Reactions Hector Valdés* , 1 , Claudio A. Zaror 2 , Martin Jekel 3 1 Laboratorio de Tecnologías Limpias, Universidad Católica de la Santísima Concepción, Concepción 4030000, Chile 2 Departamento de Ingeniería Química, Universidad de Concepción, Concepción 4030000, Chile 3 Department of Water Quality, Berlin Technical University, Berlin 10623, Germany Abstract: Benzothiazoles are emerging chemical pollutants mainly coming from leather, paper and rubber industries; due to their use as: herbicides, corrosion inhibitors, anti-freezers, and vulcanisation accelerators. This article presents experimental data on ozone treatment of benzothiazole contaminated waters. The effect of the initial concentration of benzothiazole, ozone dosage, temperature (10-30 °C), and pH (2-9), on ozonation removal rate were assessed at bench scale. Experimental results show that reaction between ozone and benzothiazole could be approximated to a second-order kinetic law. Kinetic parameters for direct and indirect ozone reactions are estimated and temperature dependence of rate parameters is evaluated. Moreover, an initial degradation pathway of benzothiazole ozonation is proposed. Keywords: Benzothiazole; Emerging pollutants; Kinetic modelling; Ozone; Radicals Introduction In recent years, concern about the presence of emergent pollutants in the environment has grown. Among them, micro-contaminants such as benzothiazole (BT) and its derivatives (2-hydroxybenzothiazole, 2- methylbenzothiazole, 2-mercaptobenzothiazole) have raised researchers’ attention (1-5). Benzothiazoles (BTs) have been suggested to induce tumours, to be allergenic, and toxic to aquatic organisms (6). BTs have wide occurrence in the environment due to their great variety of applications. BTs are normally used as fungicides in the leather and paper industry, as herbicides, as corrosion inhibitors in cooling water, as antifreeze for automobiles, and mainly, as vulcanisation accelerators in rubber production (7). BTs have been detected not only in wastewaters from rubber additive manufactures and tanneries, but also in municipal wastewaters, rivers, soils, superficial waters, estuarine sediments, and constructed wetlands (8-15). There are some doubts about BTs biodegradation (16, 17). Thus, great research efforts have been dedicated to study BTs biodegradation using acclimatised activated sludge and pure-culture bacterial strains (16, 18-20). Unfortunately, conventional biological treatment systems are not suitable to destroy this type of organic micro-pollutants since most of them are not metabolised as a carbon source. *Corresponding author; E-mail address: hvaldes@ucsc.cl They are mainly eliminated by a bio-sorption mechanism (21). Hence, advanced oxidation processes (AOPs), such as, ozonation, H 2 O 2 /UV, photo-assisted Fenton, direct photolysis, photolysis in the presence of La 3+ – TiO 2 suspension and iron oxides, and catalytic ozonation using activated carbon and volcanic sand have been evaluated as treatment alternatives to remove BTs from contaminated waters (22-30). Regarding benzothiazole (BT) removal using single ozonation, only one study has been reported in the literature so far (24). Experimental data about BT ozonation is still scarce and further information is needed in view to process design and operation. Within this context, this article gives new insights about the influence of operating conditions such as initial concentration of BT, ozone dosage, and temperature on BT removal rate. Moreover, a possible initial pathway of BT ozonation mechanism in water is elucidated and a kinetic modelling is presented. Finally, molecular ozone and radical contributions to the overall ozonation rate are analysed and the implications for process design are discussed. Experimental and Methods Materials BT (96% purity) was supplied by Sigma-Aldrich (St. Louis, Missouri, USA). Tert-butyl alcohol (t- BuOH) (> 99% purity) was used here as a radical trapping, obtained from Merck (Darmstadt, Germany). Sodium 4-chlorobenzoate (CBA) (> 98% purity) was Unauthenticated Download Date | 7/26/18 5:15 AM