Granular titanium dioxide and silicon-doped titanium dioxide as reusable photocatalysts for dye removal

In this study, photocatalytic oxidation of methylene blue (MB) and malachite green (MG) dyes was investigated using granular pure titanium dioxide and silicon-doped granular titanium dioxide as photocatalysts. Both catalysts were used repeatedly throughout the photocatalytic oxidation experiments. The effect of initial dye and catalyst concentration on photocatalytic oxidation was investigated. The photocatalytic oxidation followed first-order kinetics for both catalysts. The efficiency of photocatalytic oxidation increased with the increasing catalyst concentration and decreased with the increasing dye concentration. In a 60-min reaction using granular titanium dioxide, removal efficiencies of MB and MG at 20 g/100 mL catalyst loading and 10 mg/L initial concentration were 83% and 93.3%, respectively. In a 60-min reaction using granular silicon-doped titanium dioxide, the removal efficiencies of MB and MG at 5 g/100 mL catalyst loading and 10 mg/L initial concentration were 90.2% and 91.6%, respectively.