Synthesis of fibrous silica titania catalysts for photodegradation of ibuprofen

Abstract

In recent decades, the occurrence of pharmaceutically active compounds in wastewater has emerged as one of the major environmental issues due to its toxicity and adverse impact towards human beings and aquatic life. Photocatalytic degradation is one of the promising techniques for degrading organic compounds. Among the photocatalysts, titania (TiO2) is the most attractive since it is a non-hazardous compound and eco-friendly. However, it has a low photocatalytic performance. This present study was focused on the photodegradation of ibuprofen (IBP) using modified TiO2 namely fibrous silica titania (FST) as photocatalyst. FST was prepared using the hydrothermal method under different molar ratios of toluene and water. The catalysts were characterised using X-ray diffraction, ultraviolet-visible spectrophotometer diffuse reflectance spectroscopy, nitrogen adsorption-desorption, field emission scanning electron microscope, transmission electron microscopy, Fourier transform infrared, and electron spin resonance. The increase in molar ratio of toluene and water has resulted in increase in particle size and surface area with reduction of crystalline anatase TiO2. The highest distribution of active site (Si-O-Ti bond), terminal silanol and defeated site hydroxyl were observed in the catalyst FST(6:1), thereby showing the highest performance in degrading IBP. The photocatalytic performance of the catalysts towards degradation of 10 mg L-1 IBP under visible light at pH 7 and 0.375 g L-1 catalyst after 4 hours was in the following order: FST(6:1) (90%)> FST(5:1) (80%)> FST(7:1) (71%)> commercial TiO2 (67%). Kinetic study shows that the degradation of IBP followed the pseudo first order Langmuir-Hinshelwood model. The response surface methodology study for FST(6:1) catalyst demonstrated good significance of model with a high coefficient of determination (R2=0.937) while reusability study displayed that the catalyst was still stable after 5 cycles. The employment of catalyst on degradation of other pollutants revealed that the performance was above 20% degradation, suggesting the potential use of the catalysts for various wastewater treatments.