Synthesis of the mixed oxides of iron and quartz and their catalytic activities for the Fenton-like oxidation

Four mixed oxides of iron and silica including quartz/amorphous iron(III) oxide (Q1), quartz/maghemite (Q2), quartz/magnetite (Q3) and quartz/goethite (Q4) were prepared and characterized by XRD, BET surface area and chemical analyses. Catalytic activity of four mineral oxides was examined by employing methyl red (MR) as a model compound for the Fenton-like oxidation at two pH values (5 and 7). It was found that their catalytic activities follow the order Q4 > Q1 > Q2 > Q3 at pH 5, while the trend is modified at pH 7. Dye adsorption to the catalyst changed significantly with the pH value. The highest catalytic activity of all solids at pH 5 is probably due to the electrostatic interactions between the dye molecules and surface functional groups of catalyst at this pH value. The mixed oxides catalysts exhibited low iron leaching, good structural stability and no loss of performance in second reaction cycle.