On the Preparation of TiO_2-Sepiolite Hybrid Materials for the Photocatalytic Degradation of TCE: Influence of TiO_2 Distribution in the Mineralization

摘要

Hybrid structured photocatalysts based on sepiolite, an adsorbent, and TiO_2 were prepared by extrusion of ceramic dough and conformed as plates. The influence of the photocatalyst configuration was studied either by including TiO_2 in the extrusion process (incorporated materials) or by coating the sepiolite plates with a TiO_2 film (coated materials). The influence of the OH~- surface concentration in the photocatalytic performance was studied by treating the ceramic plates at different temperatures. The samples were characterized by N_2 adsorption-desorption, MIP, SEM, XRD, and UV-vis-NIR spectroscopy and tested in the photocatalytic degradation of trichloroethylene (TCE) as a target VOC molecule. Most of the catalysts presented high photoactivity, but considerable differences were observed when the CO_2 selectivity was analyzed. The results demonstrate that there is a significant effect of the catalyst configuration on the selectivity of the process. An intimate contact between the sepiolite fibers and TiO_2 particles for incorporated materials with a corncob-like structure favored the migration of nondesirable reaction products such as COCI_2 and dichloroacetyl chloride (DCAC) to the adsorbent, reacting with OH" groups of the adsorbent and favoring the TCE mimeralization.