983772 - Toluene Degradation by Advanced Oxidation Process Using o₃/uv and uv/tio₂/o₃ Reactors (Student Poster 12)

Atmospheric pollution has been caused great interest of the researchers, especially about some specific pollutants such as volatile organic compounds (VOC). These can prejudice human health causing headache, breathing problems and part of VOC has carcinogenic and mutagenic characteristics. VOC can also intensify environmental issues like photochemical smog, tropospheric ozone and greenhouse effect. Based on this, several techniques have been developed in order to control VOC emissions; they can be divided in two groups: recuperative and destructive techniques. The first group aims at VOC transfer phase, that is, transform gaseous VOC to liquid or solid phase. The second group intends at the destruction of VOC, converting them in less harmful compounds or even them complete mineralization resulting in water and carbon dioxide. Among the destructive techniques, advanced oxidation processes have been highlighted on the last decades such as heterogeneous photocatalysis. In this process a semiconductor solid is employed as a catalyst, humidity is necessary as a source of radicals and a radiation source is used in order to provide the photocatalystic reaction. Heterogeneous photocatalysis has been proved an interesting process to degrade VOC. However aromatic compounds degradation has been a challenge, once they can cause the catalyst deactivation. In order to avoid this, some approaches can be done such as metal or ozone additions. Therefore, this work proposed toluene degradation by heterogeneous photocatalysis with ozone addition and influence of its concentration was evaluated. The experiments were conducted in a system using two annular ascending flow reactors each one composed by a titanium cylinder containing a quartz tube with an UV-C lamp centralized in its interior. The first reactor was ozone photolytic process (O3/UV) and in the second, the quartz external wall was partially coated with titanium dioxide (TiO2), also ozone was inserted in this reactor (O3/TiO2/UV). Different concentrations of ozone were studied (from 0 % to 7 %) modifying space time. Toluene concentration was fixed on 100 ppmv (on average). As results, this system and the ozone addition avoided the catalyst deactivation. Besides this it was observed that the system with higher ozone concentration achieved greater toluene conversion comparing to the system with lower ozone concentration. Thus, heterogeneous photocatalysis with ozone addition could be applied to treat aromatic VOC in small industrial sources.