Nanocomposites and nanomaterials

Nanocomposites based on polymer and inorganic matrices for removal of soluble uranium compounds from aqueous solutions 
Perlova O.V.1, Dzyazko Yu.S.2, Martovyi I.S.1
1 Odessa I.I. Mechnikov National University, 2 Dvoryanska Str., 65082 Odesa, Ukraine
E-mail: ism_odesa@ukr.net
2 V.I. Vernadskii Institute of General and Inorganic Chemistry of the NAS of Ukraine, 32/34 Palladin ave., 03142 Kyiv, Ukraine

Different nanocomposites, which possess sorption ability towards soluble uranium(VI) compounds are considered in this work. Different synthesis methods are analyzed. The authors used the approach that provides incorporation of inorganic particles into previously formed inorganic or polymer matrices. The matrices are commercially available (ion exchange resins) or synthesized (amorphous titanium or zirconium oxides). As a modifier, a number of inorganic compounds are used: hydrated oxides and hydrophosphates, advanced carbon nanomaterials, cobalt hexacyanoferrate(II) et al. The composites are coarse-dispersive; this allows us to use them as fillers of sorption columns. It is stressed that the additions provide selective sorption of U(VI) compounds from multicomponent solutions. Sorption ability of nanocomposites strongly depends on the state of incorporated nanoparticles: non-aggregated formations accelerates sorption, aggregates and agglomerates mainly slow down it. It is explained by different effect of particles on the porous structure of ion exchange polymer. Depending on the particle location in one or other pores, they squeeze, screen or stretch hydrophilic pores, where ion exchange occurs. This is due to additional osmotic pressure caused by functional groups of inorganic modifier. Main regularities of particle formation in polymers are considered. Theoretical approach, which is based on Ostwald-Freundlich equation, has been proposed. This approach takes into consideration ion exchange capacity of polymers, the amount of reagents and other experimental conditions of the modifier deposition. Theoretical forecast has been confirmed by the data of transmission electron microscopy. 
It is noted that speciation of U(VI)-containing ions affects sorption. It is especially important for sorption on nanocomposite inorganic materials, since their sorption ability strongly depends on pH.  The modifiers expand this interval. Main regularities of regeneration of the composites are considered. A number of reagents, such as solutions of HCl, HNO3, NaHCO3, NaOH, EDTA were proposed. It is stressed that the nanocomposites are suitable for multiple usage.