Abstract: 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,δMnO2 and αMnO2 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 δMnO2 αMnO2 > 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 δMnO2 had a 1.5～3.2 times higher reaction rate than αMnO2.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 yegrass root exudates,the oxidation of 2,4DCP was decreased in the suspension of αMnO2 while increased in that of δMnO2.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 δMnO2 due to its strong adsorption toward Cu,as compared with that of αMnO2.

Key words: Soybean (Glycine max L.), Allelopathy, Hydroxy phenylacetic acid