Degradation of Congo Red dye by a Fe2O3@CeO2-ZrO2/Palygorskite composite catalyst: Synergetic effects of Fe2O3.

A newly designed Fe2O3@CeO2-ZrO2/Palygorskite heterogeneous Fenton catalyst with high degradation efficiency toward Congo Red (CR) is reported. The iron oxide (Fe2O3) was used as the originator of hydroxyl radicals (OH), CeO2-ZrO2 was used as an efficient matrix of Fe2O3 to enhance the oxidation performance, and the Palygorskite (Pal) played the role of substrate and adsorbent. A synergetic effect of the catalyst was realized by enhancing the adsorption capacity and dispersibility of CeO2-ZrO2 and Fe2O3 nanoparticles, and also due to charge transfer between these two species. The products were characterized by XRD, FTIR, SEM, TEM, XPS, VSM and nitrogen adsorption-desorption isotherms. The catalytic activities were evaluated in terms of many reaction parameters. The removal efficiency of CR was up to 95% on Fe2O3@CeO2-ZrO2/Pal under optimized conditions (Pal accounted for 30% of the catalyst mass fraction and Ce/Zr atoms molar ratio = 8:2, T = 30 °C, pH = 3.4, 4 g L-1 catalyst, 40 mM H2O2 and 500 mg/L CR), the product also has shown good reusability. Both α-Fe2O3 and CeO2-ZrO2 played important roles in the generation of hydroxyl radicals, which determined the catalytic efficiency of the composite catalyst. Fe2O3@CeO2-ZrO2/Pal was proven to be a promising candidate in the field of heterogeneous Fenton catalysis.