Photocatalytic Oxidation of Different Carbohydrates by bare and Ag-deposited TiO2 under UV Light Irradiation

Abstract

In this work we investigated the comparative optical activity and photo degradation properties of different carbohydrates such as glucose, sucrose, starch and carboxymethylcellulose by titanium and metal loaded titanium oxide (Ag loaded titanium oxide prepared by photodeposition and impregnation hydrogen reduction method). The degradation rate of carbohydrates was detected by polariometer and HPLC and its complete mineralization was confirmed by GC. The starch and carboxymethylcellulose (polysaccharide) because of their structural complexity showed slow degradation rate as compare to sucrose (disaccharide) and glucose (monosaccharide). The mechanism involves the production of electron-hole (e-- h+) pair by photo excited semiconductor particle (TiO2), which is responsible for oxidation and reduction reaction of adsorbed species on the TiO2 surface. Holes oxidize water to hydroxyl radical, which are responsible for degradation of carbohydrates. Silver loaded showed the better degradation activity as compare to bare TiO2 because metal loaded TiO2 inhibit the recombination of electrons and holes and enhance photocatalytic activity. After five hour photocatalytic reaction with the metal loaded TiO2 complete degradation of glucose and sucrose was observed and some industrially value added compound was detected. However polysaccharides were showed slow degradation at same reaction time.