Enhanced Degradation of Methyl Orange with CoFe2O4@Zeolite Catalyst as Peroxymonosulfate Activator: Performance and Mechanism

CoFe2O4@zeolite (CFZ) was prepared by using a co-precipitation hydrothermal method and used for synthetic dyes degradation by activating peroxymonosulfate (PMS). Comprehensive characterizations suggest that CoFe2O4 nanoparticles composing porous shell layer is uniformly covered on Na-A zeolite. The specific surface area of CFZ is 107.06 m(2)/g, three times that of the original zeolite. Since CFZ has a saturation magnetization of 29.0 A center dot m(2)center dot kg(-1), it could be separated efficiently by magnetic separation. Catalytic degradation experiments indicate that the removal of methyl orange (MO) in the CFZ/PMS system is much higher than that using CFZ or PMS alone. Under the optimum condition ([MO]=50 mg/L, [PMS]=1.0 mmol/L, 0.2 g/L CFZ, pH 8 and T=25 degrees C), MO removal efficiency is up to 97.1%. Effect of various factors, including pH, PMS and CFZ dosage, MO concentration and presence of coexisting anions, on the catalytic performance of CFZ is carefully studied. Reactive oxygen species quenching experiments suggest that O-1(2) and O-2(center dot-) play a dominant role in the degradation process. CFZ shows excellent recycling performance that the MO removal is declined by only 2.4% after 5 cycles. Catalytic degradation mechanism of the CFZ/PMS system is explored in detail.