Synthesis of magnetic silica catalyst by a biocompatible method

CUELLO, NATALIA I.; OLIVA, MARCOS I.; BENZAQUÉN, TAMARA B.; ELÍAS, VERÓNICA R.; EIMER, GRISELDA A.

Buenos Aires

Congreso; WCCE11 - 11th WORLD CONGRESS OF CHEMICAL ENGINEERING. IACCHE - XXX INTERAMERICAN CONGRESS OF CHEMICAL ENGINEERING. CAIQ2023 - XI ARGENTINIAN CONGRESS OF CHEMICAL ENGINEERING. CIBIQ2023 - II IBEROAMERICAN CONGRESS OF CHEMICAL ENGINEERING; 2023

It is of interest to synthesize magnetic nanomaterials for the removal of aquiferous pollutants, which are easily recoverable for recycling. For this purpose, a mesoporous silica molecular sieve of type SBA-15 [1] was sintered and modified by the wet impregnation method using an ethanolic solution of the selected iron precursor to a nominal loading of 10 wt.%. In a typical synthesis, 0.75 g of the matrix was dispersed in the precursor solution at room temperature and then ethanol was slowly removed by rotary evaporation at 333 K for 20 min. The resulting materials were heated for 6 h at 773 K in N2 atmosphere. The samples were named Fe/SBA(a) when the precursor used was Fe(NO3)3.9H2O and Fe/SBA(b) for Fe(AcAc)3 (Aldrich 97%). The presence of hexagonal mesoporous structure channels of the synthesized materials was verified by: N2 Adsorption and Desorption Isotherms and Transmission Electron Microscopy images. The physicochemical characterization of the materials was carried out through UV-Vis and XPS spectroscopy measurements. While for the analysis of their magnetic properties, their hysteresis cycles were measured in a VSM magnetometer at room temperature (Figure). As can be seen, the Fe/SBA(a) sample (M = 5.23 Am2/Kg) reaches higher magnetization values than the Fe/SBA(b) sample (M = 1.45 Am2/Kg) at 1.3 T. To perform a quantitative analysis, the curves of both samples were fitted by the sum of three contributions: linear paramagnetic, ferromagnetic, and superparamagnetic. In addition, measurements were performed following FC-ZFC protocols in a SQUID magnetometer. It should be noted that due to the size of the nanospecies formed and their dispersion within the matrix, the type of oxide cannot be identified by XRD at a high angle. Then, it was necessary to look for another technique such as Mossbauer Spectroscopy. The latter indicated that both materials are in a superparamagnetic regime at room temperature, due to this a low temperature analysis was performed identifying a maghemite phase in the Fe/SBA(a) sample and hematite in the case of Fe/SBA(b). These results would indicate that this synthesis, using Fe(NO3)3.9H2O as the metallic precursor, would be promising for its magnetic properties.