Hard meso/macroporous iron oxide/iron silicate macrospheres obtained by the multi‐templating technique

Abstract

BACKGROUND The aim of this work was to develop a cheap and easy method for the synthesis of porous iron oxide/iron silicate composite materials in the form of spheres to replace their corresponding counterparts in powder form. Macrospheres with diameters in the range 1.2–1.3 mm were prepared by the spray‐gelling technique using the multi‐templating method. Iron nitrate and tetraethyl orthosilicate were used as iron and silica sources respectively. Chitosan played a dual role (pore‐ and shape‐generating agent), while other inexpensive and easily accessible biomaterials including yeast and gelatin were used as pore generators. By this technique can be obtained metallosilicates or metal oxides/metallosilicates containing high amounts of metal incorporated within the silica framework. RESULTS The iron oxide/iron silicate composite beads were characterized by nitrogen sorption, scanning electron microscopy (SEM), energy‐dispersive X‐ray (EDX), Fourier transform infrared (FTIR), Raman, X‐ray diffraction (XRD), diffuse reflectance (DR) ultraviolet (UV)–visible and X‐ray photoelectron spectroscopy (XPS) analyses. Wide angle XRD indicated the presence of iron oxides on the surface of sample. XPS, FTIR, Raman and UV–visible analyses showed that the samples contained both intra‐framework as well as extra‐framework iron species. SEM images indicated that the macrospheres were endowed with large pores. The iron oxide/iron silicate beads exhibited good catalytic activity in the hydroxylation reaction of phenol with hydrogen peroxide. CONCLUSION This synthesis method allowed the obtaining of spherical shaped particles with large pores which exhibited good mechanical, thermal and chemical stability. Owing to their size, hardness and shape, these materials can be easily handled, recovered and reused. © 2019 Society of Chemical Industry