Nanocomposites and nanomaterials

Nanoporous sorbents based on modified TiO2 for removal of U(VI) from aqueous solutions 
Perlova O.V.1, Dzyazko Yu.S.2, Perlova N.O.1, Palchik A.V.2, Kudelko K.O.2
1 Odessa I.I. Mechnikov National University, 2 Dvoryanska Str., 65082 Odesa, Ukraine
E-mail: n.perlova@ukr.net
2 V.I. Vernadskii Institute of General and Inorganic Chemistry of the NAS of Ukraine, 32/34 Palladin ave., 03142 Kyiv, Ukraine

Synthetic composite nanomaterials, such as sorbents based on hydrated oxides of multivalent metals, are practically the exclusive type of materials possessing anion exchange properties. This feature is realized mainly in acidic and neutral media, it is possible to remove anions, which contain heavy metals, from liquid wastes of industrial plants and from ground and mining water. In order to provide selectivity towards one or other ions, the sorbents are modified with both organic and inorganic compounds.
The inorganic nanomaterials based on TiO2 have been obtained. First of all, titanium sol was obtained using electrodialysis method, hydrogel granules were precipitated using a special gelling agent. During azeotropic drying, large grains of hydrated titanium dioxide (HTD) were formed. Other sample was obtained by co-precipitation of HTD and Co2[Fe(CN)6] from mixed aqueous solution with a NH4OH solution. At last, the third sample was obtained from sol of insoluble titanium hydroxocomplexes containing Co2[Fe(CN)6]. The samples were investigated with methods of IR spectroscopy, TEM and SEM. Specific surface was estimated with technique of nitrogen adsorption-desorption. Regarding the samples, which were obtained from titanium sol, regular nanopores (3 nm) dominates within the interval of pore size of 2-100 nm. This is due to primary nanoparticles (about 6 nm) and large aggregates (pores between them are larger than 50 nm). As for the sample obtained by precipitation from the solution, micropores make sufficient contribution to porosity.
Sorption properties of the nanomaterials were investigated on the example of U(VI)-containing ions. Capacity of the sorbents towards U(VI) has been found to reach 200-230 mg g-1 at рН 5-7 and sorbent dosage of 0.5 g dm-3. Modified sorbents demonstrate higher sorption capacity than the pristine HTD sample. Moreover, they show shorter period, during which sorption equilibrium is reached. The modifier (Co2[Fe(CN)6]) expands the region of optimal pH values, more complete regeneration is realized in this case.