Photocatalytic degradation of trichloroethylene in water using TiO2 pellets

A recirculating system of aqueous trichloroethylene (TCE) solutions through the packed bed reactor with TiO2 pellets has been developed in order to mi neralize TCE without difficulties for filtration and recovery of catalyst. The TiO2 pellets prepared by sol-gel method have photocatalytic activity si milar to commercially available PC-101 and PC-102 in the powder form and to ST-B11 pellets. in batch experiments with TiO2 powders, Degussa P-25 is th e most active photocatalyst, which indicates that specific surface area is not an important factor controlling the photocatalytic activity in aqueous solutions. The degradation rates of TCE in the recirculating system with Ti O2 pellets decreased in the presence of H2O2, while were remarkably acceler ated by adding S2O82-. The presence of S2O82- ions more than 0.01 mod dm (- 3) completely suppressed hole-electron recombination and mineralized 50 ppm TCE with the 2h irradiation. In a reactor without TiO2 photocatalysts, TCE was photodegraded by SO; radicals which produced by photodissociation of S 2O82-. The degradation rates increased with increase of the initial S2O82- concentration. However, ICE was not mineralized but converted to intermedia tes which were slowly degraded to Cl- by continuing the irradiation. (C) 20 01 Elsevier Science Ltd. All rights reserved.