The influence of cobalt loading in cobalt-supported aluminum pillared montmorillonite on the kinetic of Oxone® activated oxidative degradation of tartrazine

Abstract

A series of aluminum pillared montmorillonite impregnated with different cobalt loadings (1–10) mass% were investigated as catalysts in oxidative degradation of organic water pollutant, model azo dye (tartrazine), in the presence of Oxone®. Oxone® has potassium monopersulfate as an active component which is a precursor of sulfate anion radicals. With the increase of cobalt loading up to 4 mass% the efficiency of catalysts increased. The catalytic tests revealed that the sample impregnated with 4 mass% of cobalt had the best catalytic activity within investigated series. The presence of a new cobalt-containing phase was identified in samples impregnated with 5 mass% and 10 mass% of cobalt. This finding indicated that although these samples had a higher content of catalytically active component i.e., cobalt, the presence of a new cobalt phase was less favorable for Oxone® activation and formation of sulfate anion radicals. The effect of the different cobalt loading on the reaction kinetics was investigated. The pseudo-first-order kinetic model was found to be the most appropriate to fit the experimental data for all investigated catalysts under defined experimental conditions. Both decolorization and degradation of aryl moieties had the highest pseudo-first-order rate constant for catalyst impregnated with 4 mass% of cobalt.