CoFe/SBA-15 catalyst coupled with peroxymonosulfate for heterogeneous catalytic degradation of rhodamine B in water

CoFe/SBA-15 catalysts were prepared by simultaneous incipient wetness impregnation using Co(NO3)2·6H2O and Fe(NO3)3·9H2O as the precursors and SBA-15 as the support. The catalysts were used to activate generation of sulfate radicals from peroxymonosulfate (PMS) for rhodamine B (RhB) dye degradation in aqueous solutions. The catalyst was characterized using X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy and energy-dispersive X-ray spectroscopy, transmission electron microscopy, and vibrating sample magnetometry. The effects of the Co and Fe loadings and calcination temperature on the catalytic performance, catalyst reusability, and kinetics and mechanism of catalytic oxidative degradation of RhB in the presence of CoFe/SBA-15 and PMS were investigated. The results show that the predominant Co-Fe oxide loaded on the support was the composite CoFe2O4, which provided the active catalytic sites, and was present in the SBA-15 matrix. The surface area, pore volume, and mean pore diameter of 10Co9.5Fe/SBA-15-700 were 506.1 m2/g, 0.669 cm3/g, and 7.4 nm, respectively, lower than those of SBA-15. 10Co9.5Fe/SBA-15-700 consisted of rod-like aggregates with diameters greater than 0.25 μm. It had a magnetic intensity of 8.3 emu/g; therefore, magnetic separation was feasible. 10Co9.5Fe/SBA-15-700 showed good catalytic activity and stability, with a RhB degradation rate higher than 96% and Co leaching lower than 32.4 μg/L. The catalytic oxidative degradation of RhB in the presence of FeCo/SBA-15 and PMS obeyed first-order kinetics, and the degradation rate increased with increasing CoFe/SBA-15 and PMS dosages and with decreasing initial reactant concentrations. Quenching tests showed that sulfate radicals played a dominant role in RhB catalysis. CoFe/SBA-15 maintained high catalytic activity and good stability during 10 recycling runs, with a RhB degradation rate greater than 84%, Co and Fe leaching for each run lower than 72.1 and 35 μg/L, respectively. CoFe/SBA-15 is an efficient catalyst for PMS oxidation, and has potential applications in the removal of refractory organics such as RhB in water.

Graphical AbstractRhodamine B (RhB) in solution was adsorbed by CoFe/SBA-15 that activated PMS; Co2+ contributed to electron transfer and the sulfate radicals produced attacked the RhB molecules.Figure optionsDownload as PowerPoint slide