Salih F M, Pillay A E
Department of Clinical and Biomedical Physics, College of Medicine and Health Sciences, Sultan Qaboos University, Al-Khod 123, Sultanate of Oman.
J Water Health. 2007 Sep;5(3):335-40. doi: 10.2166/wh.2007.029.
Titanium dioxide photocatalysed water disinfection is induced by the interaction of light with TiO(2), which generates highly reactive free hydroxyl radicals (OH()). These free radicals create lethal damage that leads to bacterial death. Normally, decreasing TiO(2) particle size increases the area of light interaction. This may possibly increase the concentration of OH() generated and hence increases disinfection efficiency. Moreover, decreasing the particle size increases the force of attraction between the particles and cells, which could create aggregates that may contribute to the local OH() concentration. In the present investigation cells of Escherichia coli were used as the test microorganism, TiO(2) as the photocatalyst and sunlight as the light source. Four different surface areas of TiO(2) particles corresponding to 10, 50, 80-100 and > or =300 m(2) g(-1) were tested at a concentration of 1 g l(-1). Disinfection efficiency increased with increasing the surface area producing a maximum between 80-100 m(2) g(-1) followed by a reduction at > or =300 m(2) g(-1). The reduction in the efficiency at this relatively high surface area was attributed to the increase in the local concentration of OH(). This increase may be high enough to initiate radical-radical interaction that would compete with bacterial cells and reduce the chance of bacterial cell-radical interaction taking place. Moreover, the phenomenon of TiO(2) aggregation with bacterial cells plays an important role, and the extent of aggregation increases with decreasing particle size. Such aggregation could augment the concentration of OH(*) within the cell vicinity. This suggests that surface area is a key factor in determining the efficiency of disinfection, and that concentration is a vital factor.
二氧化钛光催化水消毒是由光与TiO₂相互作用引发的，该过程会产生高活性的游离羟基自由基（OH*）。这些自由基会造成致命损伤，导致细菌死亡。通常情况下，减小TiO₂颗粒尺寸会增加光的相互作用面积。这可能会增加生成的OH浓度，从而提高消毒效率。此外，减小颗粒尺寸会增加颗粒与细胞之间的吸引力，这可能会形成聚集体，有助于提高局部OH浓度。在本研究中，使用大肠杆菌细胞作为测试微生物，TiO₂作为光催化剂，阳光作为光源。在浓度为1 g l⁻¹的条件下，测试了对应10、50、80 - 100和≥300 m² g⁻¹的四种不同表面积的TiO₂颗粒。消毒效率随着表面积的增加而提高，在80 - 100 m² g⁻¹之间达到最大值，随后在≥300 m² g⁻¹时下降。在这个相对较高的表面积下效率降低，归因于OH局部浓度的增加。这种增加可能足够高，引发自由基 - 自由基相互作用，与细菌细胞竞争，减少细菌细胞与自由基相互作用发生的机会。此外，TiO₂与细菌细胞的聚集现象起着重要作用，聚集程度随着颗粒尺寸减小而增加。这种聚集可以提高细胞附近OH的浓度。这表明表面积是决定消毒效率的关键因素，而浓度是一个重要因素。
