Optimization of photocatalytic performance of TiO2 coated glass microspheres using response surface methodology and the application for degradation of dimethyl phthalate

Hollow glass microspheres coated with photocatalytic TiO2 (HGM-TiO2), recently became commercially available and have the distinct advantages of easy separation and recovery after treatment. With this in mind, we determined the optimum conditions for hydroxyl radical generation from HGM-TiO2 photocatalysis using response surface methodology (RSM). The hydroxyl radical yield and its average generation rate are critical parameters for practical applications of TiO2 photocatalysis. In this study, terephthalic acid was used as a hydroxyl radical trap because of the selective formation of the readily. detectable hydroxyl radical adduct, 2-hydroxy terephthalic acid. Three independent variables, including loading of HGM-TiO2, concentration of terephthalic acid and irradiation time, were investigated. The 3D response surface graphs of hydroxyl radical yield and average hydroxyl radical generation rate indicated that optimum conditions of loading of HGM-TiO2, concentration of terephthalate acid and irradiation time were 8.0 g/L, 4.0 mM, and 20 min, respectively. Under these optimized conditions, we measured the photocatalysis employing HGM-TiO2 for the remediation of dimethyl phthalate (DMP), as a representative compound for problematic phthalate acid esters. HGM-TiO2 photocatalysis leads to the rapid destruction of DMP and there is a linear correlation between the DMP destruction and hydroxyl radical production. The results of our study demonstrate RSM can be used to readily determine the optimal conditions for hydroxyl radical production and the subsequent treatment of target compounds may be correlated to the hydroxyl radical production during HGM-TiO2 photocatalysis. (C) 2013 Elsevier B.V. All rights reserved.