[Surface chemical behavior of 2,4-dichlorophenol in presence of metal oxides].

To understand the surface chemistry of phenolic pollutants in the presence of metal oxides, this paper studied the reactions of 2,4-dichlorophenol with metal oxides in a kinetic and batch experiment. The results showed that amorphous ferric oxyhydroxide, goethite, delta-MnO2 and alpha-MnO2 were the potential oxidizing agents of natural and xenobiotic organic compounds. The oxidation rate of 2,4-DCP on the surface of these metal oxides was in order of delta-MnO2 > alpha-MnO2 > iron oxides. It was observed from the pseudo-first-order kinetics that the reaction rates of manganese oxides were 3-50 times higher than those of iron oxides, and delta-MnO2 had a 1.5-3.2 times higher reaction rate than alpha-MnO2. Root exudates had a significant effect on the oxidation ability of metal oxides through changing the surface characteristics or involving in the reaction process. Upon the addition of ryegrass root exudates, the oxidation of 2,4-DCP was decreased in the suspension of alpha-MnO2 while increased in that of delta-MnO2. The coexistence of Cu probably influenced the oxidation process of 2,4-DCP on the surface of metal oxides. A greater negative effect of Cu on the oxidation of 2,4-DCP was also observed in the suspension of delta-MnO2 due to its strong adsorption toward Cu, as compared with that of alpha-MnO2.