Sorption Of Uranium
SORPTION of URANIUM
WITH TITANUM SILICATES ZEOLITES
О.I. Zakutevsky, Т.S. Psareva, S.I. Meleshevich, N.I. Shenk,
V.А. Kanibolotsky, V.V. Strelko
Institute for Sorption and Endoecology Problems,
Ukrainian National Academy of Sciences,
General Naumov st. 13, 03680 Kyiv, Ukraine
It is known that synthetic titanium silicates zeolites are high-selection sorbents for extraction of radioisotopes of cesium and strontium from a liquid radioactive waste. The titanium silicates capacity to absorb uranium from water solutions provides an opportunity to use them as general purpose sorbents for clearing sewage and liquid radioactive waste from radionuclides.
Despite its high sorption capacity along with thermal, chemical and radiation stability, titanium silicates sorbents are still underestimated and not applied widely on a large scale. This is due, primarily, to the complicated process of synthesis and strict requirements to the conditions of the process.
The research of improving of the conditions of the process of titanium silicates zeolites synthesis was carried out in ISPE NAS of Ukraine, namely: the preliminary boiling of an initial solution to remove gaseous products of reaction. As a result, the pressure in an autoclave was considerably reduced, thus, period of synthesis was essentially reduced. To improve ion-exchange properties the titanium silicates were modified by ions of niobium.
Samples of titanium silicates of different composition and physicochemical properties and of different conditions of their synthesis were explored as sorbents for uranium.
The study of the dependence of sorption capacity (А) of titanium silicates in uranium solutions from рН has shown that at the range рН 4-7 uranium sorption was stable, the maximal quantity of 9,7 mg/g the value A reached at рН ~ 5. The study of influence of the background electrolyte on absorption of uranium with titanium silicates has shown, that introduction of such salts as acetate, sulphate, nitrate or soda (considerably) reduces the
sorption of uranium. The capacity of uranium to form complexes results in the formation of complex ions of large radius in a solution. These ions are hard to penetrate into micropores and interplanar strata of sorbent of size less than 4Å.
The examination of sorption kinetics of uranium with titanium silicates at concentration of uranium of 5мg/l allows drawing a conclusion that under these conditions a limiting stage is the exterior diffusion.
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