Fotodegradación oxidativa de fenol con catalizadores TiO2-Canálisis de la respuesta fotoquímica de la fase carbonosa

Resumen

[EN] The increasing contamination of wastewater streams by organic species refractory to conventional water treatment methods has promoted the development of new technologies capable of degrading these pollutants. In this regard, advanced oxidation processes have gained growing attention as emerging clean and efficient technologies for wastewater treatment, since they can promote the mineralization of the pollutant through the generation of highly oxidative species. Among them, heterogeneous photocatalysis offers a great potential due to several advantages: the breakdown of the pollutant is carried out at ambient conditions, the catalyst can be reused and atmospheric oxygen is used as oxidant. In this work, photodegradation of phenol in aqueous solutions has been investigated as an alternative for the abatement of this hazardous organic compound commonly present in industrial wastewaters. One way to increase the efficiency of the process consists on loading the photoactive specie (TiO2) onto a carbon support. The enhanced photo-activity observed between the two materials towards the photodegradation of a wide range of pollutants in aqueous phase is ascribed to different mechanisms depending on the nature and the loading of the carbonaceous matrix. In order to elucidate the phenomena involved in the photocatalytic response of these materials, a thorough synthesis, characterization and photocatalytic performance evaluation of hybrid TiO2-C composites using different carbon sources as supports were carried out. Additionally, and taking into account the porous nature of some of these materials, the individual contributions of adsorption and photocatalysis to the overall pollutant removal yield were evaluated. For that purpose, phenol adsorption experiments were performed in the presence of activated carbons with varied surface chemistry. The results obtained confirmed that the carbonaceous support does not only significantly modify the rate and efficiency of phenol removal from the solution but also influences the oxidation pathway, which determines the degree of mineralization achieved in the photocatalytic reaction. Moreover, and beyond the synergistic effect observed between the two photocatalyst components, some carbon materials have revealed their ability to generate hydroxyl and superoxide radicals –main oxidant species responsible for phenol mineralization– when exposed to UV light in aqueous media. It has also been observed that although the presence of mineral matter in the composition of the carbon material can be beneficial for the photocatalytic reaction, some pure carbon matrices have also shown their ability to form highly reactive species, highlighting their intrinsic photoreactivity. This finding offers new perspectives for carbon materials and opens the door to explore innovative applications related with environmental applications.