Heterogeneous fenton oxidation of refractory dye rhodamine B in aqueous solution with mesoporous Fe/SBA-15

Abstract

An Fe-loaded mesoporous silica SBA-15, Fe/SBA-15, was prepared by incipient wetness impregnation, characterized by X-ray diffraction (XRD), N2 adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques and used for heterogeneous Fenton oxidation of dye Rhodamine B (RhB) in aqueous solution. The characterization showed that the Fe/SBA-15 retained a mesoporous structure with a long-range ordered arrangement, reduced pore diameter and surface area, and existed as agglomerates of rod-like crystallites with a mean diameter of 0.6 μm. The Fe species occurred both inside and outside the support pores in the form of α-Fe2O3 crystallites. The removal of RhB in the presence of Fe/SBA-15 and H2O2 was shown to be caused by the synergistic effects of adsorption and catalytic oxidative degradation, and was closely related to Fe/SBA-15 dosage. Removal was almost independent of initial solution pH, with approximately 93% achieved at an Fe/SBA-15 dosage of 0.15 g∙L-1, initial RhB concentration of 10.0 mg∙L-1, H2O2/Fe3+ molar ratio of 2000:1; initial solution pH of 5.4 and 21 °C. The Langmuir monolayer adsorption capacity of the Fe/SBA-15 was 99.11 mg∙g-1. In addition, Fe/SBA-15 can be easily regenerated by soaking in H2O2 then reused for up to six runs, with RhB removal greater than 80% and Fe leaching below 0.1 mg∙L-1 (or 0.6% (mass fraction)) for each run. A removal mechanism for RhB by Fe/ SBA-15 and H2O2 was proposed based on the quenching tests, UV-Vis spectra, and gas chromatography-mass spectrometry (GC-MS) analysis. The heterogeneous Fenton catalyst Fe/SBA-15 can be applied to remove non-biodegradable organics such as dye RhB.