Veniamin V. Zheleznov

Colloid stable sorbents for cesium removal: Preparation and application of latex particles functionalized with transition metals ferrocyanides

In this paper we suggest a principally new approach to preparation of colloid stable selective sorbents for cesium uptake using immobilization of transition metals (cobalt, nickel, and copper) ferrocyanides in nanosized carboxylic latex emulsions. The effects of ferrocyanide composition, pH, and media salinity on the sorption properties of the colloid stable sorbents toward cesium ions were studied in solutions containing up to 200 g/L of sodium nitrate or potassium chloride. The sorption capacities of the colloid sorbents based on mixed potassium/transition metals ferrocyanides were in the range 1.3-1.5 mol Cs/mol ferrocyanide with the highest value found for the copper ferrocyanide. It was shown that the obtained colloid-stable sorbents were capable to penetrate through bulk materials without filtration that made them applicable for decontamination of solids, e.g. soils, zeolites, spent ion-exchange resins contaminated with cesium radionuclides. After decontamination of liquid or solid radioactive wastes the colloid-stable sorbents can be easily separated from solutions by precipitation with cationic flocculants providing localization of radionuclides in a small volume of the precipitates formed.

Sorption Recovery of Strontium from Seawater

Sorption recovery of strontium from seawater and prospects of using selective sorbents for treatment of seawater or mixtures of liquid radioactive wastes (LRW) with seawater to remove 90Sr are examined. A comparative analysis is made of characteristics of various sorbents. The most of the sorbents studied demonstrate low distribution coefficients and selectivity with respect to strontium, being unable to provide efficient removal of 90Sr from seawater. The exceptions are new sorption reagents developed by the authors, which show promise for treatment of LRW to remove strontium. The possible mechanism of strontium sorption with these sorbents is suggested.

Sorption of cesium radionuclides with composite carbon fibrous materials

Sorption of composite sorbents produced by a combined method of thermal treatment and electrochemical and chemical deposition of transition metal ferrocyanides stabilized with latex emulsions onto a fibrous carbon matrix for cesium radionuclides was studied.

Composite sorbents for recovery of cesium radionuclides

Sorption properties of composite sorbents produced by electrochemical deposition of a siloxaneacrylate emulsion impregnated with transition metal ferrocyanides onto a fibrous carbon matrix for cesium radionuclides were studied.

Nanostructured microtubes based on TiO2 doped by Zr and Hf oxides with the anatase structure

The nanostructured microtubes based on TiO2 have been prepared on the carbon fiber template using the sol-gel method. The microtubes consist of nanoparticles of metal oxides: TiO2/ZrO2 and TiO2/HfO2. The dependence of microtubes morphology and nanoparticles structure on the synthesis conditions has been studied using the methods of SEM, SAXS, and Raman spectroscopy. It has been demonstrated that at the stoichiometric ratio of up to 0.04 for Zr/Ti and up to 0.06 for Hf/Ti microtubes consist of uniform nanoparticles with the anatase structure. Along with further increase of the dopants content in the microtubes composition, nanoparticles acquire the core-shell structure. It has been suggested that nanoparticles have a core composed of the solid solutions Ti1-xZrxO2 or Ti1-xHfxO2 and a shell consisting of zirconium or hafnium titanate. The fabricated Zr- and Hf-doped TiO2 materials were investigated in view of their possible use as anode materials for Li-ion batteries. Charge- discharge measurements showed that the doped samples manifested significantly higher reversibility in comparison with the undoped TiO2. The method opens new prospects in synthesis of nanostructured materials for Li-ion batteries application.

Sorption properties of nanostructured potassium aluminosilicate

The ability of synthetic nanostructured potassium aluminosilicate (PAS) KAlSi3O8·1.5H2O with the specific surface area of 105 ± 5 m2 g−1 to take up cesium ions was studied. The maximal sorption capacity of PAS in sorption of Cs+ ions from cesium carbonate solutions containing no other salts is ∼3.7 mmol g−1. In Cs+ sorption from solutions containing no other salts, the sorption capacity is the lowest at pH 1; it increases with pH, reaching a maximum at pH 10.8. The effect of salt background (various concentrations and ratios of KCl and NaCl) on the sorption properties of PAS was examined. The sorption capacity decreases to the greatest extent (to 0.25 mmol g−1) in solutions containing the K+ and Na+ ions simultaneously at concentrations of 68 and 517 mM, respectively. The dependence of the cesium sorption on the concentration of nitrates (NaNO3, KNO3, NH4NO3) and the kinetics of the cesium sorption from aqueous NaNO3 solution were studied with the 137Cs tracer. The highest distribution coefficients (up to 12000 mL g−1) are observed in 137Cs sorption from NaNO3 solutions. The degree of the 137Cs sorption reaches a maximum (92 ± 4%) in sorption from 0.01 M NaNO3 solutions at the sorption time of 4 h.

Cesium uptake by pentacyanoferrate(II) complexes with O-containing derivatives of chitosan

ABSTRACT Here we report on synthesis of new organic-inorganic materials based on products of interaction between sodium aminoprusside and polymer ligands. Fourier transform infrared (FT-IR) and UV-visible spectroscopy and thermogravimetry were used to investigate the structure and stability of the complexes. It was found that ion and ligand exchange were the main reactions of the interaction of sodium aminoprusside with water-soluble polymer salts. All other composites in the Co(II) form were characterized in terms of sorption capacities and distribution coefficients (Kd) for cesium ions. The highest values of distribution coefficients were obtained for polyampholyte chitosan derivatives.

Latex Particles Functionalized With Transition Metals Ferrocyanides for Cesium Uptake and Decontamination of Solid Bulk Materials

Decontamination of spent ion-exchange resins, corrosion-unstable metal structures, soil, ground, and construction materials contaminated by fission, corrosion and transuranic radionuclides remains one of the most urgent and complicated ecological problems. Among the existing methods having different efficiencies in regard to such materials decontamination, application of selective sorbents put into a humid medium to be decontaminated (ground, bulk materials) appears to be rather extensive. However, the efficiency of such an approach is significantly limited by difficulties concerned with uniform sorbent distribution in porous media and completeness of spent sorbents removal for final disposal. In this paper we suggest a principally new approach to preparation of colloid-stable selective sorbents for cesium uptake using immobilization of transition metals (cobalt, nickel, and copper) ferrocyanides in nanosized carboxylic latex emulsions. The effects of ferrocyanide composition, pH, and media salinity on the sorption properties of the colloid-stable sorbents toward cesium ions were studied in solutions containing up to 200 g/1 sodium nitrate or potassium chloride. The sorption capacities of the colloid sorbents based on mixed potassium/transition metals ferrocyanides were in the range 1.45–1.86 mol Cs/mol ferrocyanide with the highest value found for the copper ferrocyanide. It was shown that the obtained colloid-stable sorbents were capable to penetrate through bulk materials without filtration that makes them applicable for decontamination of solids, e.g. soils, zeolites, spent ion-exchange resins contaminated with cesium radionuclides. After decontamination of liquid or solid radioactive wastes the colloid-stable sorbents can be easily separated from solutions by precipitation with cationic flocculants providing localization of radionuclides in a small volume of the precipitates formed. Besides, functionalized latex particles can be used for preparation of carbon fiber/ferrocyanide composite materials for cesium uptake using electrodeposition method. Application of the carbon fibers as an inert support for ferrocyanides, in general, significantly improves the sorption kinetics, but washing out of ferrocyanide fines from the fiber surface limits the potential of such materials. When ferrocyanides are deposited in a form of nanocrystals stabilized by latexes which undergo electropolymerization on the fiber surface, the thin polymeric film formed substantially improves the stability of the composite and prevents loss of ferrocyanide during sorbent application. The effect of electrodeposition conditions on composite morphology, ferrocyanide loading and cesium distribution coefficient in media with different salinity has been discussed.Copyright

Effect of Hf-doping on electrochemical performance of anatase TiO2 as an anode material for lithium storage

Hafnium-doped titania (Hf/Ti = 0.01; 0.03; 0.05) had been facilely synthesized via a template sol–gel method on carbon fibre. Physico-chemical properties of the as-synthesized materials were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis, scanning transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry analysis and Brunauer–Emmett–Teller measurements. It was confirmed that Hf4+ substitute in the Ti4+ sites, forming Ti1–xHfxO2 (x = 0.01; 0.03; 0.05) solid solutions with an anatase crystal structure. The Ti1–xHfxO2 materials are hollow microtubes (length of 10–100 µm, outer diameter of 1–5 µm) composed of nanoparticles (average size of 15–20 nm) with a surface area of 80–90 m2 g–1 and pore volume of 0.294–0.372 cm3 g–1. The effect of Hf ion incorporation on the electrochemical behaviour of anatase TiO2 in the Li-ion battery anode was investigated by galvanostatic charge/discharge and electrochemical impedance spectroscopy. It was established that Ti0.95Hf0.05O2 shows significantly higher reversibility (154.2 mAh g–1) after 35-fold cycling at a C/10 rate in comparison with undoped titania (55.9 mAh g–1). The better performance offered by Hf4+ substitution of the Ti4+ into anatase TiO2 mainly results from a more open crystal structure, which has been achieved via the difference in ionic radius values of Ti4+ (0.604 Å) and Hf4+ (0.71 Å). The obtained results are in good accord with those for anatase TiO2 doped with Zr4+ (0.72 Å), published earlier. Furthermore, improved electrical conductivity of Hf-doped anatase TiO2 materials owing to charge redistribution in the lattice and enhanced interfacial lithium storage owing to increased surface area directly depending on the Hf/Ti atomic ratio have a beneficial effect on electrochemical properties.

Neutron activation determination of gold in technogenic raw materials with different mineral composition

The methods used to determine the gold content in the technogenic objects of gold mining were analyzed regarding their no homogeneity and complexity of chemical and mineral compositions. A possible application of the neutron activation analysis (NAA) with the use of the californium source of neutrons for determining the content of fine-grained and extra-fine-grained gold in the technogenic objects, including the bottom-ash waste of energy providers, is considered. It was demonstrated that the chemical composition of the sample affects the neuron flux distribution in the sample, which can essentially distort the results of the NAA. In order to eliminate the possible systematic errors, investigations of the effect of the sample mineral composition on the results of the gold determination using the NAA, loading a large mass of the rock (3–5 kg) into an activation zone and using four types of matrix, silicate, carbon-containing, iron-containing, and titanium magnetite, were carried out. It was shown that there is no significant difference between the dispersal of the fluxes of thermal and resonance neutrons emitted from 252 Cf during activation of the gold-containing technogenic samples with different mineral compositions.