Heterogeneous Catalytic Ozonation of Aqueous p-nitrophenol over MIL-100(Fe) Metal–Organic Framework

Abstract

ABSTRACT Metal–organic frameworks have been extensively studied in catalysis owing to their unique physicochemical properties. However, this class of materials has not yet been directly applied to the catalytic ozonation of organic pollutants. In this study, MIL-100(Fe) was synthesized by a solvothermal method and characterized by powder X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, N2 adsorption–desorption and scanning electron microscopy. A range of reaction conditions such as pH, solute concentration and catalyst content were applied to investigate the catalytic activity of our MIL-100(Fe) sample for the ozonation of p-nitrophenol in water. According to the experimental results, at a neutral initial pH, the catalytic ozonation of p-nitrophenol proceeded mainly through radical reactions, whereas in the absence of the MIL-100(Fe) catalyst, ozone could react with p-nitrophenol via the direct reaction pathway. The catalyst achieved a conversion of up to 98% and chemical oxygen demand removal of up to 75%. Moreover, our MIL-100(Fe) catalyst retained this performance for seven cycles of operation, which offers potential applications for metal–organic frameworks as catalysts in wastewater treatment.