Microwave-assisted catalytic degradation of methyl orange in aqueous solution by ferrihydrite/maghemite nanoparticles

Six-line ferrihydrite was successfully prepared by precipitation method and characterized with XRD, SEM, TEM, BET and FTIR spectroscopy. The as-prepared ferrihydrite was used as catalyst for the degradation of methyl orange (MO) in an artificial dye wastewater without adding any oxidant. It was found that the ferrihydrite nanoparticles with average size of about 90-220 nm exhibited a high adsorption capability to MO and the dye molecules obey Langmuir type of adsorption. Batch degradation experiments show that the catalytic degradation of MO could be remarkably improved by coupling with microwave irradiation. The initial pH value of MO solution exerted notable influence on the degradation reaction and the optimal degradation efficiency was obtained under neutral conditions. Radical scavenger measurements indicated that OH radicals could generate during the catalytic process even without adding oxidant. We proposed that the microwave irradiation facilitates the generation of active oxygen species derived from water and/or oxygen dissolved in water, which are responsible to the excellent performance of the MW-assisted catalytic process. (C) 2017 Elsevier Ltd. All rights reserved.