| The objective of this research is to advance our knowledge of the hydrogen peroxide decomposition mechanism and kinetics in the presence of three types of iron oxides; amorphous ferrihydrite, crystalline goethite and semi-crystalline iron oxide, which are important in the subsurface environment. The influences of several environmental factors, such as pH, carbonate concentration, natural organic matter, and phosphate concentration were investigated and the catalytic activity toward oxidation of quinoline, a model pollutant, examined.;Results show that the decomposition of hydrogen peroxide can be described by a rate expression which was first order with respect to hydrogen peroxide concentration and first order with respect to iron oxide concentration. The mass based catalytic activity of iron oxides toward hydrogen peroxide decomposition decreased as the order of ferrihydrite ;The adsorption of phosphate onto iron oxides was well described by single-site Langmuir isotherms at pH 6 and 7 in the presence of weakly co-adsorbing carbonate species. The phosphate surface adsorption capacity was similar on a surface area base for the three iron oxides and slightly decreased with increasing pH value. The influence of phosphate on the catalytic activity of iron oxide could be modeled using a simple single-site adsorption isotherm assuming that phospirate and carbonate occupied sites were inactive in catalyzing hydrogen peroxide decomposition.;Ferrihydrite exhibited no catalytic activity toward quinoline oxidation, semi-crystalline iron oxide showed little activity, and goethite the greatest on a surface area basis. The stoichiometric efficiency of quinoline oxidation by hydrogen peroxide in the presence of goethite did not depend on the solid-to-water ratio in batch reactors, nor was it affected by the presence of carbonate and phosphate which decreased the rate of hydrogen peroxide decomposition. |
