Sepiolites as supporting material for organic sensitisers employed in heterogeneous solar photocatalysis

Triphenylpyrylium cation (TPP + ) was supported onto sepiolites to be used as heterogeneous solar photocatalyst. The procedure to prepare this material was a formal ion exchange process: the desired amount of TPP + was added to an aqueous suspension of the sepiolite and stirred in the dark for 24 h. Then the mixture was filtered and the solid dried in an oven at 105 °C. Infrared and UV–vis spectroscopy indicated the presence of TPP + in the new material; solid TOC analysis showed that the process was quantitative, allowing easy control of the sepiolite loading. Difractogrammes indicated that no significant modification of the sepiolite structure occurred. Despite the low ion-exchange ability of this clay, important loadings were accomplished, most probably due to the removal of some Mg 2+ in acidic medium; this was demonstrated by the presence of magnesium cation in the filtered aqueous fraction obtained in the synthetic process. Finally, the efficiency of the pyrylium-loaded sepiolite was tested using ferulic acid as target pollutant; results were very satisfactory, and important percentages of photo-oxidation were achieved.