Photoactivity of TOPO-capped TiO2 nanocrystals for the degradation of endocrine disrupting chemicals

• Main Authors: Pin-Han Lo, 羅品涵
• Other Authors: Sue-Ming Chang
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/09438073102607318645

碩士 === 國立交通大學 === 環境工程系所 === 96 === Heterogeneous photocatalytic reaction for decomposition of endocrine disrupting chemicals (EDCs) has attracted much attention. The efficiency of photodecomposition is limited by the recombination of electrons and holes and the adsorption ability between catalysts and target compounds. In this study, modification of titanium dioxide (TiO2) with trioctylphosphine oxide (TOPO) was prepared by a non-hydrolytic sol-gel method. The TOPO-capped TiO2 exhibited high adsorption ability for EDCs. The partition coefficients of phenol, BPA and estrone in the presence TOPO-capped TiO2 are 0.15, 3.09, and 28.64 l/g, respectively. In contrast, Degussa P25 adsorbs EDCs inefficiently. In the case of photocatalytic reaction, photocatalysis of EDCs follows Langmuir-Hinshelwood model. The initial rates for decomposition of phenol and bisphenol A (BPA) by TOPO-capped TiO2 are 1.4 and 3.2 times, respectively, higher than those by Degussa P25. The kinetic rate constants of phenol and bisphenol A are 7.3�e10-2 and 1.4�e10-1 ppm�eg�emin-1�em-2, respectively, in the presence of TOPO-capped TiO2, which are 0.9 and 2.7 times, respectively, higher than those in the P25 slurry (8.2�e10-2 and 5.2�e10-2 ppm�eg�emin-1�em-2). The smaller rate constant of TOPO-capped TiO2 for decomposition of phenol is due to that the modifier occupied active sites. The adsorption coefficients of phenol and bisphenol A are 2.2�e10-2 and 6.4�e10-2 l/mg, respectively, in the presence of TOPO-capped TiO2, which are 2.2 and 5.8 times, respectively, higher than those in the P25 slurry (1.0�e10-2 and 1.1�e10-2 l/mg). The photocatalytic mechanism of TOPO-capped TiO2 mainly involves direct photodecomposition of these adsorbed EDCs by photo-generated charges rather by hydroxyl radicals which is normally occurred in the P25-based system. In addition, the intensity of trapped holes and electrons in TOPO-capped TiO2 are much higher than that in P25. These results reveal that TOPO-capped TiO2 improved interfacial charge transfer. In summary, the TOPO assists partition of EDCs onto the TiO2 surface and facilitates interfacial charge transfer. These contributions improve photocatalytic activity of TOPO-capped TiO2.