Iron-copper bimetallic nanoparticles supported on hollow mesoporous silica spheres: The effect of Fe/Cu ratio on heterogeneous Fenton degradation of a dye

A series of iron-copper bimetallic nanoparticles supported on hollow mesoporous silica spheres with different Fe/Cu ratios were prepared using a simple post-impregnation and sodium borohydride reduction strategy. Different Fe/Cu ratios were obtained by addition of various amounts of ferric and copper salts. The catalysts were characterized by XRD, XPS, nitrogen physisorption, SEM and TEM. To explore the difference of catalytic reactivity among the various FeCu/HMS composites, Fenton-like catalytic oxidation of orange II was chosen as the model catalysis reaction. The catalytic results showed that the catalytic activity depended highly upon the Fe/Cu ratio. Particularly, 1/3 (2Fe6Cu/HMS) is the optimum Fe/Cu mass ratio to achieve the best catalytic activity. Based on the results of detection of OH radicals and cyclic voltammograms, the important origin of the synergetic effect in 2Fe6Cu/HMS is considered as the combination of iron and copper species, which can accelerate the interfacial electron transfer in redox cycles of Fe³⁺/Fe²⁺ and Cu²⁺/Cu⁺ pairs, followed by the increase in the OH radical generation. The 2Fe6Cu/HMS also possesses less pH dependence and maintains its high activity even under alkaline conditions. The optimal parameters in the degradation of 100 mg L^-1 orange II are 27.4 mM of H₂O₂ with 1.0 g L^-1 of catalyst, performed at a pH of 7.0 and 30 degree celsius. It is worth noting that 2Fe6Cu/HMS also possesses potential to treat a high concentration of dye pollutants. 77.7% of orange II was removed when conducted at 1000 mg L^-1 initial dye concentration. The stability and recoverability of the composite catalyst were assessed it exhibited a good performance after 5 consecutive runs. The as-synthesized composite catalyst proved to be an attractive alternative for dye wastewater treatment applications.