Photocatalysis of antibiotic sulfamethazine by titanium dioxide supported on activated carbon

• Main Author: Wong, Tze Ying.
• Other Authors: Lim Teik Thye
• Format: Final Year Project
• Language: English
• Published: 2011
• Subjects: DRNTU::Engineering::Environmental engineering::Water treatment
• Online Access: http://hdl.handle.net/10356/45212
• Institution: Nanyang Technological University

A bifunctional photocatalyst, i.e. titanium dioxide supported on activated carbon (TiO2/AC) was synthesized with the sol-gel method. The prepared composite was then characterized by various methods such as X-ray diffraction, Brunauer-Emmet-Teller analysis, gravimetric analysis, scanning electron microscopy and transmission electron microscopy. It was found that the TiO2/AC composite was mesoporous (pore size = 3.8 nm) and comprised both anatase and rutile phases. TiO2 was found to be anchored on the surface of AC. To test the catalytic ability of TiO2/AC, photocatalytic degradation of sulfamethazine (SMZ) with UV-A irradiation (maximum wavelength = 365 nm) was investigated at an optimum loading ratio (50% TiO2/50% AC). It was observed that TiO2/AC had a much higher SMZ photodegradation rate than naked TiO2 because TiO2/AC had a much larger specific surface area, which contributed to enhanced adsorption of SMZ on the solid-liquid interface where mineralization of SMZ by photogenerated holes, •OH and O2•- occurred. The effects of pH and aqueous matrix species (Cl-, SO42-, HCO3-, methanol and hydrogen peroxide at 1 mM and 100 mM concentrations) on the adsorption and photodegradation of SMZ were also investigated. The adsorption decreased with increasing pH due to ionic repulsion between the negatively charged SMZ and ionized surface functional groups of TiO2 and AC at higher pH. There was a slight increase in photodegradation rate at pH 3.0 due to enhanced adsorption, and an even greater increase at pH 9.0, which was caused by the higher concentration of •OH. Cl- at 100 mM concentration was shown to enhance the adsorption. However, Cl- showed inhibitory effect on the photodegradation of SMZ due to scavenging of •OH radicals by Cl-, although the effect was significantly lesser at higher Cl- concentration. HCO3- inhibited both the adsorption and photodegradation processes. SO42- had a trivial effect on adsorption and photodegradation. Methanol did not affect SMZ adsorption on the composite but inhibited photodegradation with increasing methanol concentration. H2O2 at 1 mM concentration showed inhibitory effect on photodegradation because of reduced adsorption caused by the oxidation of TiO2/AC surface. Nonetheless, there was a slight enhancement when 100 mM H2O2 was added due to electron scavenging and increased •OH production.