Sustainable production of pure silica from rice husk waste for preparation of ordered nanostructured mesoporous silica.

CARRARO PAOLA M.; CUELLO, NATALIA I.; BENZAQUÉN, TAMARA B.; 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

During recent years, a persistent interest of researchers has been in the possibility of developing new, safe, non-toxic, and environmentally sustainable materials using waste and more environmentally friendly processes, reducing the environmental impact we place on our planet. The most efficient way to lower the negative impacts is designing and innovating in the manufacturing processes, taking into account different aspects such as energy source, reactants, and use and generation of secondary materials. The crop residues represent one of the largest biomass resources globally. Among them, rice husk (RH) is an abundant and sustainable waste biomass available in the world [1]. In most of the papers, the silica sources used for the synthesis of mesoporous materials are metal alkoxides such as tetraethylorthosilicate (TEOS), tetra-methoxysilane (TMOS), and tetramethylammoniumhydroxide (TMAOH), which are relatively expensive and bring toxic effect.In this sense, the main objective of the present work was synthesizing siliceous mesoporous materials of MCM-41and SBA-15 type using a natural, non-toxic, and cheap source of silica; aiming at a more economical, safer, environmentally friendly synthesis that allows adding value to this agricultural residue. The pure silica supports were modified by wet impregnation with different loadings of Fe (2.5 and 5% w/w) according to Benzaquen et al. 2019 [2]; and characterized using various physico-chemical techniques. The synthetized compounds were evaluated for efficient photocatalytic degradation of different EDCs in aqueous medium, applying the photo-Fenton heterogeneous reaction, also analyzing its effects on adsorption.All the materials showed good structural regularity, determined by XRD and N2 adsorption-desorption isotherms at 77 K, typical of mesoporous materials. Mesoporous materials of SBA-RHA type presented lower areas than that of MCM-RHA materials. Moreover, in all materials a decrease in specific area and pore volumes are observed with Fe loading increasing. This may be related to the presence Fe oxides as clusters and/or nanoparticles both inside the channels and on the external surface, which could be blocking some mesopores, causing a decrease in these values. The iron chemical species were inferred by UV-vis RD spectroscopy and programmed thermal reduction. Thus, the MCM-RHA materials presented higher reduction temperatures than that of SBA-RHA materials, which is indicative of a high dispersion of iron species, that strongly interact with the support.These mesostructured materials have been successfully tested in the photo-Fenton heterogeneous degradation of different endocrine disruptors in water. The results showed that the catalyst with the lowest iron loading (2.5 %p/p of Fe) presented the highest degradation of contaminants, probably due to the presence of Fe active species, highly dispersed and interacting with the support surface. In order to improve the pore volume, specific area, versatility and flexibility of the material, we are seeking to obtain nanometric structures in the form of fibers by electrospinning.