Photocatalytic degradation of trichloroethylene in water using TiO2 pellets

A recirculating system of aqueous trichloroethylene (TCE) solutions through the packed bed reactor with TiO(2) pellets has been developed in order to mineralize TCE without difficulties for filtration and recovery of catalyst. The TiO(2) pellets prepared by sol-gel method have photocatalytic activity similar to commercially available PC-101 and PC-102 in the powder form and to ST-B11 pellets. in batch experiments with TiO(2) powders, Degussa P-25 is the 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 TiO(2) pellets decreased in the presence of H(2)O(2), while were remarkably accelerated by adding S(2)O(8)(2-). The presence of S(2)O(8)(2-) 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 TiO(2) photocatalysts, TCE was photodegraded by SO; radicals which produced by photodissociation of S(2)O(8)(2-). The degradation rates increased with increase of the initial S(2)O(8)(2-) concentration. However, ICE was not mineralized but converted to intermediates which were slowly degraded to Cl(-) by continuing the irradiation. (C) 2001 Elsevier Science Ltd. All rights reserved.