The oxidation of toluene sorbed on activated carbon in the presence of H2O2 and manganese oxide

Abstract

We investigated the oxidation of toluene sorbed on activated carbon (AC) in the presence of hydrogen peroxide (H2O2) and pyrolusite (MnO2). Sorbed toluene was prepared by reacting a toluene-saturated solution and AC. The amounts of sorbed toluene (mg of toluene/g of AC) decreased as the amounts of AC were increased. The reaction was conducted in a gas-purging (GP) reactor and the gas flow at the outlet of a GP reactor was carefully maintained. As a result, the percentage of toluene captured by ORBO tube was 28% in the control system with pure water. When H2O2 was catalyzed by AC (i.e. this forms a hydroxyl radical by electron transfer), approximately 17% of the desorbed toluene was oxidized and 68% of toluene remained on AC which was similar to the control system. However, when pyrolusite (650 mg/L) was added together with H2O2 (10,000 mg/L), only 5% of toluene was captured by the ORBO tube and 55% of toluene remained on AC, which indicated that both desorbed and sorbed toluene was oxidized. Moreover, toluene oxidation increased when concentrations of pyrolusite and H2O2 were increased. It was suggested that superoxide anion, which is generated by the reaction of H2O2 and pyrolusite, might stimulate toluene desorption and then toluene in the aqueous phase could be oxidized by hydroxyl radical.