Relationship between oxidative degradation of 2-mercaptobenzothiazole and physicochemical properties of manganese (hydro)oxides

Abstract

Environmental context. Manganese (hydro)oxide is one kind of the most important natural minerals that are capable of oxidising organic contaminants with a wide range of functionality. However, the oxidative reactivity of manganese (hydro)oxides for organic pollutant degradation may depend on their individual physicochemical properties. It is important to determine a relationship between their oxidative reactivity and physicochemical properties. Abstract. The oxidative reactivity of manganese (hydro)oxides is important for geochemical transformation of organic pollutants. Here, 2-mercaptobenzothiazole (MBT) degradation by six manganese (hydro)oxides, including γ-MnOOH, β-MnO2, α-MnO2, γ-Mn2O3, δ-MnO2, and MO-700, were investigated with different initial MBT concentrations, manganese (hydro)oxide dosages and pH values. The results show the oxidative reactivity of manganese (hydro)oxides towards MBT degradation strongly depends on their physicochemical properties. Specific surface area and reduction potential of manganese (hydro)oxides were positively correlated with MBT degradation rates, whereas pH at the point of zero charge (pHPZC) of manganese (hydro)oxides and apparent activation energy (Ea) were negatively correlated. A high average oxidation state with the same chemical valence always corresponds to high oxidative reactivity. Such findings provide some insights into understanding the transport and fate of organic pollutants in the presence of different manganese (hydro)oxides in the natural environment.