The oxidative degradation of 2-mercaptobenzothiazole at the interface of β-MnO2 and water

Abstract To investigate the oxidative degradation of organic pollutants at the interface of manganese oxides and water, β-MnO 2 was prepared and its crystal structure and the specific surface area were examined by X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) methods, respectively. 2-Mercaptobenzothiazole (MBT) as a model chemical was used to study its oxidative degradation reaction in β-MnO 2 suspension. The experimental results showed that MBT was effectively degraded and mineralized into SO 4 2− and NO 3 − by β-MnO 2 . In the meantime, it was found that β-MnO 2 could be reductively dissolved, and aqueous and adsorbed Mn 2+ was generated. The kinetics of MBT degradation by β-MnO 2 is a function of initial MBT concentration, β-MnO 2 dosage and pH value. At pH 4.6, apparent reaction orders with respect to initial MBT concentration and β-MnO 2 dosage were determined to be 0.88 and 0.27, respectively. The initial reaction rate ( r init ) is of pH dependence with a reaction order of −0.36. The thermodynamics of MBT degradation by β-MnO 2 was also investigated, and the apparent activation energy was calculated to be 5.62 kJ/mol. The inhibited effect of carboxylic acids (oxalic, citric, tartaric, and malic acids) or metal ions (Ni 2+ , Ca 2+ , Mn 2+ and Cr 3+ ) on the oxidative degradation of MBT by β-MnO 2 was also investigated. This investigation will give some new insights for understanding the interaction of organic pollutants with manganese oxides in natural soils and sediments.