Free- and Ni-doped carbon xerogels catalysts for wet peroxide oxidation of methyl orange

The present study investigates the synthesis and catalytic oxidation performance of catalysts consisting of free- and nickel-doped carbon xerogels (CXs) that derived from carbonization of tannic acid-resorcinol-formaldehyde xerogel at 700 °C for 30 min under N2 gas flowing. Nickel-doped carbon xerogels (CX-Ni-350 and CX-Ni-500) were prepared by wet impregnation-reduction method and then thermally treated at 350 and 500 °C for 180 min under its own atmosphere, respectively. The X-ray diffraction patterns (XRD) of the obtained CX-Ni-500 catalyst revealed that three nickel metallic phases were formed in carbon matrix indicating its profound affect to improve the catalytic activity of CX. Scanning electron microscope combined with energy-dispersive spectroscopy (SEM-EDS) also indicated that wide pores and nickel particles dispersed on the surface of produced CX-Ni-500 catalyst were found. To assess the catalytic efficiency of the prepared catalysts, catalytic wet peroxide oxidation of methyl orange dye was studied. It was found that decomposition rate of MO dye was strongly dependent on the hydrogen peroxide dose, temperature, catalyst dose and initial concentration of MO dye. The catalytic decomposition of MO dye was completely achieved in 30 min by CX-Ni-500 at pH 3. The CWPO experimental results also showed that the incorporation of Ni metallic by impregnation-reduction method into CX surface dominated the decomposition efficiency of MO dye. To estimate the reusability efficiency of the prepared CX-Ni-500 catalyst, the results showed excellent catalytic activity during four CWPO cycles, affording highly decomposition of MO dye over 90% within the fourth CWPO run.