Nanocomposites and nanomaterials

Sorbents based on hydrated titanium dioxide modified with Co2[Fe(CN)6] nanoparticles for recovery of uranium species from water 
Perlova O.V.1, Dzyazko Yu.S.2, Perlova N.O.1, Palchik A.V.2, Martovyi I. S.1, Kudelko K.O.2
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

Oxide materials are attractive due to their ability to sorb both cations and anions depending on the solution acidity. In order to expend the ph interval, where ions of one or other type are sorbed, oxides are inserted into ion exchange matrix or modified with selective components. In this work, hydrated titanium dioxide (HTD) was modified with Co2[Fe(CN)6] nanoparticles. The first step of HTD obtaining was electrodialysis of the TiCl4 solution, sol was synthesized by this manner. Further hydrogel granules were precipitated using a special gelling agent. During azeotropic drying, large grains of hydrated titanium dioxide (HTD) were formed. This sample (I) contained mainly regular nanopores, a size of which was about 3 nm. These pores performed a function of nanoreactors, where Co2[Fe(CN)6] nanoparticles are synthesized (sample II). At last, the sample III was coprecipitated with Co2[Fe(CN)6]. 
As found, the point of zero charge (PZC) is 6.6-6.8 for all samples. Main features of U(VI) sorption from sulfate and nitrate solutions were investigated. U(VI) is in anionic forms in the H2SO4 medium. In general, anion sorption on oxides is depressed with pH increasing. However, sorption of U(VI) anions is enhanced, since the competition of SO42- ions becomes weaker. The removal degree of 100% for U(VI) anions was reached at for the sample II, which contained the modifier particles formed in nanoreactors. The lower values were found for the samples III (70 %) and I (50 %). The optimal dosage of HTD was 2 g dm-3; in the case of composites the dosage was smaller in 2 times. In the case of HNO3 media, U(VI) exists in cationic forms. Similarly to U(VI) anions, sorption of cations is also enhanced with the increasing pH. The removal degree is 95 % (sample II) and about 70 % (sample I) at pH 7. The sorption rate obeys the model of pseudo-first order (nitrate solutions) or pseudo-second order (sulfate media).