Optimization of hydroxyl radical formation using TiO 2 as photocatalyst by response surface methodology

Abstract

The determination of the optimum parameters for hydroxyl radicals ( OH) formation by a TiO 2 solution has been investigated by measuring the emitted fluorescence after the reaction with terephthalic acid has occurred. After UV irradiation, the terephthalic acid was transformed into 2-hydroxyterephthalic acid whose fluorescence is directly proportional to the generated OH. Optimization of hydroxyl radicals’ formation using TiO 2 as catalyst was carried out by studying the effects of irradiation time, TiO 2 concentration and terephthalic acid concentration on the production of the fluorescent HTA with an experimental design. The aim of our research was to apply response surface methodology as a chemometric method for the optimization of the reaction conditions. The combination of irradiation time, TiO 2 concentration and terephthalic acid concentration was varied at designed points of a central composite rotatable design. The three factors were found to have a significant effect upon the reaction. The optimum conditions for the reaction achievement were estimated to be 10 min for the irradiation time, 25 μg mL −1 TiO 2 concentration and 0.1 mmol L −1 terephthalic acid concentration. Afterwards, using these parameters the method was applied for the determination of the ability of several plant extract samples to scavenge the formed OH.