Tailoring the stability and photo-Fenton activity of Fe-modified nanostructured silicates by tuning the metal speciation from different synthesis conditions

Abstract

The stability and photo Fenton activity of nanoarchitectured silicates modified with Fe by the wet impregnation method were studied as a function of the used solvent, calcination temperature and iron loading. The physicochemical properties were characterized by SAXS, XRD, N2 physisorption, SEM, AA, UV–Vis DR, XPS and TPR. All solids showed long-range structural order typical of SBA-15 with high specific surface, PV and a narrow distribution of PD. The proper choice of impregnation solvent allowed tuning the iron speciation in order to obtain catalysts highly stable and efficient for their use in the azo dyes photo-Fenton degradation at pH = 3.5. Calcination temperature does not seem influence on such speciation. Isolated iron cations finely dispersed and strongly anchored on the mesoporous channels, whose formation is promoted by the use of ethanol and the low iron loading, are proposed as active sites for the photo-Fenton process. Likewise, low iron loadings also favor the higher accessibility of these sites to the reactant molecules (AO7 and H2O2). Thus, the highest dye mineralization degree was obtained by an actual iron loading of 1.31% wt. The heterogeneity of the process was confirmed. The more active solid also showed a high stability and reuse capacity, maintaining its performance.