Photodegradation of 2-chlorophenol over colloidal alpha-FeOOH supported mesostructured silica nanoparticles: Influence of a pore expander and reaction optimization

Abstract

In this work, mesostructured silica nanoparticles (MSN) were modified by the pore expander 3-aminopropyl triethoxysilane (APTES) via the sol-gel method before impregnation with a colloidal a-FeOOH-ionic surfactant (IS-FeOOH) to produce IS-FeOOH/MSNAPTES. Its properties were characterized using X-ray diffraction, Fourier-transform infrared and surface area analysis, and compared with pristine MSN, MSNAPTES and IS-FeOOH/MSNs. The results suggest that IS-FeOOH was located on the outer surface of MSN but in the pores when loaded onto MSNAPTES, while retaining its colloidal structure on both supports. It was found that the photoactivity of the catalysts toward photo-Fenton-like degradation of 2-chlorophenol (2-CP) under visible light irradiation was in the following order: IS-FeOOH/MSN (92.2%) > IS-FeOOH/MSNAPTES (77.6%) > MSNAPTES (38.7%) > MSN (17.5%). The results indicate that the presence of colloidal IS-FeOOH on the outer surface of MSN plays important role in enhancing photoactivity. Photokinetic analysis also supported this result by showing that the surface and bulk reaction was the rate-limiting step for IS-FeOOH/MSN and IS-FeOOH/MSNAPTES, respectively. The operating conditions of 2-CP degradation over IS-FeOOH/MSN were further optimized using response surface methodology. The optimum conditions were found to be 9.09 wt% of IS-FeOOH loading with 0.14 mM H2O2 at pH 5.11 and 49.9 °C to give 99.9% of the predicted value of photodegradation.