Mesoporous Silica Based Catalysts for Oxidation of Azo Dyes in Wastewater

Abstract

Iron-containing catalysts were synthesized by supporting on mesoporous silica: commercial KCC silica, μM-41 silicalite and silica gels prepared under laboratory conditions using spray drying and drying in supercritical CO2. The support samples were prepared different ways. The porous structure of the catalysts was characterized by low temperature nitrogen adsorption. The catalytic activities and stabilities were compared during oxidation of an anionic due – carmoisine – with 3 % H2O2 solution in water at 60 °C and pH 3. The initial contained 20 mg/l carmoisine, 3 g/l catalyst at the molar H2O2/carmoisine ratio equal to 459/1. The KCC based catalyst was most active and stable to leaching of the active component to the solution: 99 % conversion of carmoisine was reached in 30 min of the reaction, while the concentration of iron ions was 0,27 mg/l, i.e. below its maximal admissible concentration. When the support was pre-impregnated with aluminium, the iron leaching decreased to a half. The synthesized catalysts seem promising for treatment of wastewater containing organic contaminants.