Establishment of the Russian Academy of Sciences I. V. Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials of the Kola Science Centre of the Russian Academy of Sciences, Apatity, Russia:

L. G. Gerasimova, Chief Research Assistant, e-mail: gerasimova@chemy.kolasc.net.ru
A. I. Nikolaev, Head of Laboratory
M. V. Maslova, Leading Research Assistant
E. S. Shchukina, Research Assistant

Studied are conditions of synthesizing frame-structured titanium-containing exchanger with a structure similar to ivanyukite out of (NH₄)₂TiO(SO₄)₂·H₂O salt. To increase hydrolysis stability, partial reduction of initial solution has been fulfilled by electrochemical method with Ti⁴⁺ conversion to Ti³⁺. This expedient allows avoiding an amorphous phase generation and directing the process to creation of crystalline ivanyukite in a form of two structural modifications: trigonal (Na₄(TiO)₄(SiO₄)_3.6H₂O) and cubic (Na₃H(TiO)₄(SiO₄)_3·4H₂O); the precipitate crystallinity degree is 90–95%. Crystallization proceeds under five times system oversaturation by sodium silicate. Determined have been optimal conditions for titanium- siliceous precursor sol-gel obtaining and consequent hydrothermal transformation of the obtained gel to crystalline phase: content of Ti₂O₃ in the solution after reduction is 30–45 g/l, molar ratio TiO₂:SiO₂ = 1:4. It has been shown that the pore system (total volume of pores) of crystalline ivanyukite particles is approximately 1.5 times larger than that of X-ray amorphous samples and that it is mainly represented by mesopores of medium size, which are characterized by the most activity in sorption processes. Natrium and potassium ions situated in the ivanyukite frame space along with water provide high exchange velocity of cations absorption in sorption processes due to minimal diffusive obstacles. The reported preliminary data on sorption allow to describe the frame-structured crystalline alkaline titanosilicates as effective sorbents of cations of non-ferrous metals, strontium, as well as univalent cations, caesium in particular.

The research has been implemented thanks to the grant of the Russian Science Foundation (project No. 17-19-01522).

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