Résumé
Denitration of water was investigated by nonphotocatalytic and/or photocatalytic processes (UV-A irradiation at 365 nm) using a mixture of Ag/P25 + Pt/P25 monometallic catalysts and Ag-Pt(Pt-Ag)/P25 bimetallic catalysts (2 wt% Ag; 4 wt% Pt) prepared by drop-wise wetness impregnation of TiO2 P25 support. In the bimetallic samples, the influences of the Pt precursor (H2PtCl6 center dot 6H(2)O; K2PtCl6) and of the impregnation order of the metallic salts were examined. The highest N-2 yield (42.3%) in the nonphotocatalytic process was achieved with the Ag/P25 + Pt/P25 mixture but with ca. 12.6% NO2- yield. Photocatalytic activity was enhanced in presence of H-2 in comparison to H-2-free condition. Ag/P25 is the most active photocatalyst, however high NO2- yield is obtained (32.5%). The bimetallic samples exhibit high versatility, being active both in the non-photocatalytic and the photocatalytic processes. Low NO3- conversion and high NO2- selectivity results were obtained from impregnation of Ag first. In contrast, impregnation of Pt precursor from K2PtCl6 first effectively promoted NO3- reduction towards N-2 yield of 36% and particularly low NO2- yield of 2.7%, due the presence of metallic nanoparticles of different sizes and interaction with TiO2 with a peculiar strong Pt and Ag interaction. Best results obtained in non-photocatalytic and photocatalytic processes are almost similar.