Removal of azo-dye Acid Red B (ARB) by adsorption and catalytic combustion using magnetic CuFe2O4 powder

The effectiveness of magnetic CuFe2O4 powder as adsorbent/catalyst for the removal of azo-dye Acid Red B (ARB) from water by adsorption and subsequent catalytic combustion was studied. Magnetic CuFe2O4 powder showed excellent adsorption properties towards ARB at pH<5.5, and it could be conveniently recovered by magnetic separation technology after adsorption. The combustion decomposition of ARB in the presence or absence of CuFe2O4 was studied by a system for thermal degradation studies (STDS) and in situ FTIR. The results indicated that different reactive pathways existed for the combustion under different conditions. In the presence of CuFe2O4, the temperature needed for oxidation reaction and for combustion was 150 and 300 °C, respectively. The reaction products were observed to be SO2, CO2, H2O, and nitrate. There was neither volatile organic compound (VOCs) emitted to atmosphere during reaction nor organic matter deposited on the surface of CuFe2O4 after the combustion. Comparatively, in the absence of CuFe2O4, the oxidation and combustion of ARB required a higher temperature (300 and 500 °C, respectively) and produced a lot of toxic organic compounds emitted to atmosphere besides SO2, CO2 and H2O during the reaction. In addition, sulfate was generated instead of nitrate. The experiments of adsorption–combustion cycles demonstrated that there was no evident change in adsorption properties and catalytic activity of magnetic CuFe2O4 powder after seven cycles.