Yamazaki S, Matsunaga S, Hori K
Department of Chemistry, Faculty of Science, Yamaguchi University, Japan.
Water Res. 2001 Mar;35(4):1022-8. doi: 10.1016/s0043-1354(00)00347-x.
A recirculating system of aqueous trichloroethylene (TCE) solutions through the packed bed reactor with TiO2 pellets has been developed in order to mineralize TCE without difficulties for filtration and recovery of catalyst. The TiO2 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 TiO2 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 TiO2 pellets decreased in the presence of H2O2, while were remarkably accelerated by adding S2O8(2-). The presence of S2O8(2-) ions more than 0.01 mol dm(-3) completely suppressed hole-electron recombination and mineralized 50 ppm TCE with the 2 h irradiation. In a reactor without TiO2 photocatalysts, TCE was photodegraded by SO4- radicals which produced by photodissociation of S2O8(2-). The degradation rates increased with increase of the initial S2O8(2-) concentration. However, TCE was not mineralized but converted to intermediates which were slowly degraded to Cl- by continuing the irradiation.
已开发出一种通过装有TiO₂颗粒的填充床反应器的三氯乙烯（TCE）水溶液循环系统，以便使TCE矿化，同时不存在催化剂过滤和回收方面的困难。通过溶胶-凝胶法制备的TiO₂颗粒具有与市售粉末形式的PC-101和PC-102以及ST-B11颗粒相似的光催化活性。在使用TiO₂粉末的间歇实验中，Degussa P-25是活性最高的光催化剂，这表明比表面积不是控制水溶液中光催化活性的重要因素。在含有TiO₂颗粒的循环系统中，TCE的降解速率在H₂O₂存在下降低，而通过添加S₂O₈²⁻则显著加速。当S₂O₈²⁻离子浓度超过0.01 mol dm⁻³时，完全抑制了空穴-电子复合，并在2小时的照射下使50 ppm的TCE矿化。在没有TiO₂光催化剂的反应器中，TCE被S₂O₈²⁻光解产生的SO₄⁻自由基光降解。降解速率随初始S₂O₈²⁻浓度的增加而增加。然而，TCE没有被矿化，而是转化为中间体，通过持续照射，这些中间体缓慢降解为Cl⁻。
