Simulation of U(VI) and Co(II) sorption on montmorillonite

Radiochemistry - Sorption of U(VI) and Co(II) on montmorillonite of the Cherkassy deposit in the range pH 4.0–9.0 at ionic strengths of 0.01 and 0.1 (NaClO4) was studied. The experimental...     

Sorption of U(VI) on montmorillonite with aluminum and iron hydroxides deposited on its surface,studied in the presence of citric and oxalic acids

Sorption of U(VI) on montmorillonite from the Cherkassy deposite with Al(III) and Fe(III) hydroxides deposited on its surface (metal weight fraction 0 and 5%: M-0, MAl-5, and MFe-5) was studied in the presence of complexing agents: citric and oxalic acids. Citric acid suppresses the uranium sorption from weakly acidic solutions more strongly than does oxalic acid. At equimolar concentrations of ligands and U(VI) in solution, ternary surface complexes can be formed on the surface of the examined samples.     

Desorption of U(VI) from montmorillonite with aluminum and iron hydroxides deposited on its surface

Decontamination of uranium-containing samples based on montmorillonite from the Cherkassy deposit, with Al(III) and Fe(III) hydroxides (weight fraction with respect to metal 0 and 5%: M-0, MAl-5, and MFe-5) deposited on its surface, by desorption with complexing agents (EDTA, citric acid, oxalic acid, sodium carbonate) was studied. With respect to efficiency of U(VI) desorption from the sample surface, the ligands can be ranked in the following order: citric acid > oxalic acid > ETDA ≥ sodium carbonate. In neutral solutions, citric acid is the most effective and environmentally suitable. From M-0 and MAl-5 samples, U(VI) is desorbed completely, whereas in the case of MFe-5 about 15% of U is irreversibly bound to the surface.     

Effect of aluminum and iron hydroxides deposited on the montmorillonite surface on the U(VI) sorption

Sorption of U(VI) on montmorillonite (M) of the Cherkassy deposit, with Al(III) and Fe(III) deposited on its surface in various amounts (1 and 5 wt %), was studied. The presence of such hydroxides increases the U sorption in the range pH 4.0–8.0. The U(VI) sorption increases in the order M < [M + 1% Al(III)] < [M + 5% Al(III)] < [M + 1% Fe(III)] < [M + 5% Fe(III)]. The U sorption isotherms on all the sorbents were obtained. The effect exerted on the sorption by artificial (ethylenediaminetetraacetic acid) and natural (fulvic acids) complexing agents was examined. Original Russian Text ? G.N. Pshinko, A.A. Bogolepov, S.A. Kobets, A.A. Kosorukov, 2009, published in Radiokhimiya, 2009, Vol. 51, No. 2, pp. 187–190.     

The removal of heavy metals from aqueous solutions by montmorillonite modified with polyethylenimine

We have shown a possibility of using montmorillonite modified with polyethylenimine for the removal of ions of heavy metals (Co(II) and Ni(II) from aqueous solutions. It has been found that the employment of such a composite sorbent is promising for purification of medium- and highly-mineralized wastewaters with the neutral value of the pH. The complexation influence of the reagents on the purification process has been shown and determined a dose of a reagent for obtaining the maximum possible degree of purifying aqueous solutions.     

Influence of the nature of oxygen-containing minerals on their sorption ability toward U(VI)

Sorption of U(VI) on natural and synthetic oxygen-containing minerals was studied. With respect to the sorption ability toward U(VI), natural minerals can be ranked in the order iron-containing > aluminum-containing > silicon-containing, and synthetic minerals, in the order iron-containing ≈ silicon-containing ≫ aluminum-containing. It was demonstrated by the example of Fe(OH)₃, α-FeO(OH), and γ-FeO(OH) that crystalline minerals bind U(VI) at pH values corresponding to natural media (pH > 7.5) better than do amorphous minerals. The ionic strength does not affect the U(VI) sorption owing to formation of strong inner-sphere complexes on the mineral surface. The presence in solution of complexing agents in small amounts can enhance the U(VI) sorption owing to formation of ternary surface complexes, whereas large excess of the ligand decreases the sorption because of the shift of the equilibrium toward formation of soluble complexes migrating in the environment by long distances with water streams.     

The mechanism of the development of the synapse as the basis for its involution

The electron microscopic investigation of human brain synaptic organization in normal aging and in ischemic heart pathology in different life periods was performed. A significant quantity of desmosome-like and mixed contacts was shown. Their ultrastructural organization was similar to that of developing synapses during prenatal ontogenesis and in newborn rats. The analysis of the experimental results suggests that an appearance of desmosome-like contacts in the human brain results from synapse involution. This is supported by the observation of formation of mixed contacts which may be a transitional stage between symmetrical or asymmetrical specialized synapse and desmosome. Thus, the mechanism of synaptic involution appears to be a mirror reflection of the mechanism of its development.     

Glauconite as model material for examining deactivation of uranium-containing soils

Radiochemistry - Sorption of U(VI) on a clay illite mineral glauconite from Osykovo deposit was examined in relation to the sorption time, pH, and presence of EDTA. The equilibrium in the...