Hybrid Composites Based on Silica and Titanium(IV) Phosphate for Sorbents
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id Composites Based on Silica and Titanium(IV) Phosphate for Sorbents L. G. Gerasimovaa, *, A. I. Nikolaeva, E. S. Shchukinaa, M. V. Maslovaa, and Yu. G. Kiseleva a
Tananaev Institute of Chemistry and Technology of Rare Elements and Minerals (separate subdivision), Kola Scientific Center (Federal Research Center), Russian Academy of Sciences, Apatity, Murmansk oblast, 184209 Russia *e-mail: [email protected] Received March 11, 2020; revised May 22, 2020; accepted June 11, 2020
Abstract—Using a titania–silica precursor with the composition SiO2 ∙ TiO2 ∙ хH2O, isolated via hydrochloric acid treatment of a process waste from the dressing of apatite–nepheline ore, we have prepared a hybrid composite containing silica as a matrix for an α-Ti(HPO4)2 ∙ H2O functional filler (STP). The key step of the synthesis process is a solution-phase reaction of the precursor with phosphoric acid. Our results demonstrate that a preferable sequence of steps begins with the mechanical activation of the components of the precursor, with their phase transformations. Using a combination of subsequent heat treatment with phosphoric acid with different concentrations under atmospheric conditions and in an autoclave, we have found conditions for chemical reactions that change the composition and structure of the final product and, accordingly, its sorption activity for cesium and strontium cations. The synthesized hybrid inorganic material can be effectively used to remove radionuclides and heavy nonferrous metal cations from liquid discharges. The proposed technology significantly surpasses known processes in economic and environmental characteristics. Keywords: hybrid composites, matrix, functional filler, mechanical activation, silica, rutile, sorbent DOI: 10.1134/S0020168520110011
INTRODUCTION Hybrid composite materials are being increasingly widely used in the fabrication of products with improved physicochemical and performance characteristics [1]. They often contain crystalline fillers and an amorphous matrix. The filler determines functionality of the material and its matrix ensures chemical homogeneity and stability to various types of external influence [2]. It is worth noting that sorbents, including those containing titanium(IV) phosphate, are widely used in technologies for removing toxic elements and radionuclides from liquid discharges. Essentially no such products are manufactured in Russia, except for small plants operating in the preorder regime. Accordingly, there is currently great practical interest in the preparation of sorbents, including titanium-containing ones, which are highly demanded at present because of the great environmental problems. The synthesis and properties of such sorbents have long been the subject of rather intense research. The reason for this is that they have certain advantages over conventional materials, including organic resins, because they offer a higher ion exchange capacity, have a better chemical
stability and radiation resistance, and are well compatible with radioactive waste forms. T
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