Nanocomposites and nanomaterials

Fibrous polymer sorbents modified with nanoparticles of hydrated tin (IV) oxide for removal of anionic U(VI) compounds from aqueous solutions 
Perlova O.V.1, Dzyazko Yu.S.2, Rodyvylova R.A.1, Palchik A.V.2
1 Odesa I.I. Mechnikov National University, 2 Dvoryanska Str., 65082 Odesa, Ukraine
E-mail: Rodyvylova@ukr.net
2 V.I. Vernadskii Institute of General and Inorganic Chemistry of the NAS of Ukraine, 32/34 Palladin ave., 03142 Kyiv, Ukraine

Fibrous polymer anion-exchanger Fiban A-6 was modified with nanoparticles of hydrated tin(IV) oxide (HTO). Thermodynamical approach was applied to deposition of particles inside polymer matrix: it takes into consideration solubility of the inorganic modifier in under and oversaturated solutions, temperature, ion exchange capacity of polymer and other parameters. If no special conditions are applied to the modifier deposition, for instance, additions of complex forming agent, tin oxide was estimated to be precipitated as nanoparticles. It was a criterion for choice of this modifier. HTO was deposited in a form of non-aggregated nanoparticles. As known, namely this morphological feature provides fast sorption as well as high sorption capacity. The composites were investigated by means of SEM, TEM and porometric methods. Chemical composition of the modifier was identified by means of FTIR spectroscopy. 
The main kinetic characteristics of the sorption process were calculated using pseudo-first and pseudo-second order models, Weber-Morris and Yelovich approaches. The half-time of exchange is 10 min. (pristine fibers) and 6 min. (modified fibers). U(VI) ions are removed completely after 40 and 25 min respectively. Uranium sorption isotherms have been obtained, their modeling is carried out using Henry, Langmuir, Freundlich, Dubinin-Radushkevich, Frumkin models, constants of these equations and thermodynamic sorption parameters have been calculated. As found, sorption of carbonate forms of uranium by the studied sorbent is a spontaneous endothermic process, which is accompanied by an increase in entropy. The possibility to use the modified fibrous anion exchange resin FIBAN A-6 for extraction of small amounts of uranium from model solutions that simulated technological solutions has been established. It is interesting that increase in U(VI) concentration from 1 to 4 mg dm-3 improves the recovery of these ions (%) from 58 to 95 (pristine polymer) and from 68 to 100 (composite).