Fe_2O_3/MCM-41 as catalysts for methyl orange degradation by Fenton-like reactions

摘要

A large amount of contaminated industrial wastewater has aroused mounting concern by researchers and environmentalists. Dyes contained in industrial effluents are often quite persistent to biodegradation, which must be treated before being disposed of. In this context, the use of Fenton processes is a potential alternative to treat a wide range of dyes and other organic pollutants found in wastewater. Thus, several Fe_2O_3/MCM-41 catalysts have been synthesized in the following molar ratio of SiO_2/Fe_2O_3:10, 20,40,100, and 200. They were characterized by N_2 adsorption-desorption isotherm, X-ray fluorescence (XRF), X-ray diffraction (XRD), UV-vis spec-troscopy and H_2 temperature-programmed reduction (H_2-TPR), and applied to degrade methyl orange dye (MO) via a heterogeneous Fenton reaction. Catalytic tests revealed that SiO_2/Fe_2O_3 = 10 reached the highest activity due to greater availability of active sites which generated a larger quantity of hydroxyl (·OH) and perhydroxyl (·OOH) radicals. Furthermore, 70% of color removal has been achieved after 120 min at room temperature. Moreover, the systems moderately enhanced organic matter mineralization according to chemical oxygen demand (COD) testing. There was also catalytic activity loss in consecutive reaction cycles, which is probably due to dye molecules adsorption on active sites.