Photocatalytic decomposition of estrogens in aquatic environment by reciprocating immersion of TiO2-modified polytetrafluoroethylene mesh sheets

Photocatalytic decomposition of 17beta-estradiol (E2) and estron (E I) in aqueous solutions was carried out by use of TiO2 photocatalysts immobilized on polytetrafluoroethylene (PTFE) mesh sheets and irradiated with black fluorescent lamps. The TiO2-modified PTFE mesh sheets were stacked in a 0.51 (11 = 1 dm(3)) or 51 beaker and were reciprocatively immersed in the range of 2-4 cm at the rate of 5-120 rpm. The first-order rate constant of E2 decomposition (initial concentration, 250 mug l(-1)) was proportional to the ratio of the surface area of the TiO2-modified PTFE mesh sheets to the volume of the treated water. It was also proportional to the square root of the reciprocation rate of the TiO2-modified PTFE mesh sheets, which was mainly due to mass-transfer limited condition. In addition, it was increased with increasing temperature, which was explained by the change of diffusion rate of E2 in water. About 90% of E1 in a practical discharged water was decomposed by using the 51 reactor in 4 min with good reproducibility. Based on the results, application of this system to purification of discharged water at a sewage treatment plant could be expected. (C) 2003 Elsevier Science B.V All rights reserved.