PHOTOCATALYTIC DEGRADATION OF PHENOL BY TiOi/CARBON CATALYSTS: THE EFFECT OF IRRADIATION WAVELENGTH

摘要

Heterogeneous photocatalysis is widely recognized as an effective technology for the degradation and mineralization of recalcitrant organic compounds. In order to overcome the limitations of conventional semiconductors, carbons materials have been extensively investigated in a number of photoassisted reactions. In fact, many studies show that adding a carbonaceous component can enhance the performance of the photoactive material, being attributed to several factors associated to visible light absorption, the porosity of the carbon support, strong interfacial electronic effects, and the intrinsic photochemical activity of certain carbons [1-3]. It is well known that only photons with A<400 nm can be absorbed by TiO2 to induce the excitation of electrons from the valence to the conduction band, and that many organic compounds present a strong absorption of light in this region, leading to direct degradation in the absence of a catalyst (photolytic reaction). The origin and dependence of the carbon/light interactions with the irradiation source still remains uncertain and in the case of hybrid carbon/semiconductor catalysts, the situation is even more complex. Our recent investigations have demonstrated the photoactivity of semiconductor-free nanoporous carbons under UV and visible light [3-5] and their ability to photogenerate oxygen reactive species as the key aspect to achieve enhanced degradation yields of pollutants from solution.