[en] Using the method of thermography the properties of zirconium oxalates (ZO) synthesized during interaction of concentrated aqueous solutions of oxalic acid and zirconium oxychloride at elevated temperatures are studied. Gel-like ZO precipitation is characterized by constant composition Zr:C₂O₄^2-∼1:1 independent of the initial molar ratio of the reagents. It is shown that the loss of ZO mass proceeds in three stages. The mechanism of the thermal destruction is ZrO₂. It is found that ZO sorption properties remain unchanged in the 20-250 deg C temperature range. Sorbent heat treatment at higher than 250 deg leads to reduction of sorption capacity and loss of selectively with respect to alkaline cations

[en] Synthesis of inorganic adsorbent on the basis of zirconium hydroxide, consisting in the mixing of zirconium salt solution with urotropin and urea, dispersion of the mixture into organic liquid at 85-95 deg, washing of spherical granules of hydrogen by ammonium carbonate solution and thermal treatment at 400-600 deg for 1.5-3 h, is suggested. The prepared adsorbent has sorptional capacity towards alkaline-earth metal ions during sorption from neutral and low-acid solutions, which is 12-80 times higher than that of sorbents prepared by previously known method. 4 tabs

[en] A framework potassium titanium silicate K₂TiSi₃O₉·H₂O, compound I, was synthesized by the reaction of a titanium-hydrogen peroxide complex and SiO₃ in alkaline media under mild hydrothermal conditions (180 C). This compound was converted to the corresponding sodium phase, Na₂TiSi₃O₉·H₂O (IV) and two proton-containing phases, K_1.26H_0.74TiSi₃O₉·1.8H₂O (II) and K_0.3H_1.7TiSi₃O₉·2.4H₂O (III) by ion exchange. These products were characterized by elemental analysis, TGA, FT-IR, MAS ²⁹Si NMR, and X-ray diffraction. The ion exchange behavior of compound I and III toward alkali, alkaline earth, and some transition metal ions solutions was studied. A high affinity of the protonic form of titanium trisilicate exchanger for cesium and potassium makes it promising for radionuclide-contaminated groundwater treatment and certain analytical separations. The crystal structure of compound I was found to be isomorphous with that of the zirconium analogue and contains a framework enclosing two types of tunnels. The exchange properties were interpreted on the basis of this structure and selectivity of the Zr and Ti phases rationalized on the basis of the tunnel sizes. The structure of II was solved on the basis of a monoclinic cell, whereas the compound I phase is orthorhombic. The relationship of structure II, monoclinic, to the parent orthorhombic structure is described. Phase III yielded a complex X-ray pattern with evidence of disorder and a highly complex ²⁹Si NMR spectrum. On reexchanging with K⁺, the original crystal lattice was restored

[en] The influence of cation concentration and medium acidity on the sorption of Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺ ions by the sorbents on the basis of titanium, zirconium, tin phosphates, as well as their new modifications, containing in their structure two elements of group 4 simultaneously: titanium and tin, zirconium and tin, has been studied. Interrelation between chemical composition position, sorbent structure and selectivity of alkaline-earth metal ion absorption, has been detected

[en] 'To expand the authors efforts to provide families of inorganic ion exchangers useful on a global scale. In carrying out this objective, they will synthesize a variety of ion exchange materials, determine their structures and where necessary alter these structures to build in the desired properties. The underlying thermodynamic, kinetic and molecular basis of ion exchange behavior will be elucidated and their suitability for nuclear waste remediation will be assessed. As of September 1, 1996, they have synthesized a number of highly selective inorganic ion exchangers, determined their crystal structures and elucidated the mechanism of exchange for a number of these exchangers.'

[en] Regularities of alkali metal cations sorption by titanium-zirconium phosphate sorbents were studied. Acidity of phosphoric acid groups in ionites was determined to be 2-3 lower by a factor of 10^-2-10³ than in ortho-phosphoric acid. Simultaneous introduction of two elements of 6 group with various radii into sorbent structure permitted to perform smooth arrangement of geometric parameters of sorption centers and thus to change their selectivity

[en] A simple and convenient way of zirconium photsphate sample transfer into solution by means of treatment with hydrofluoric acid is suggested. Phosphorus and zirconium are determined in the form of molybdenum heteropolycompounds. Butanol extracts of molybdophosphate (MP) and aqueous solutions of molybdozirconophosphate (MZP) (after extractional separation of MP excess) obey Beer's law in the range up to 0.016 mg/ml for phosphorus and up to 0.09 mg/ml for zirconium. The method correctness is 1.6 and 1.35% for phosphorus and zirconium respectively

[en] Thermal behaviour of zirconium tetrametaphosphomate during its heating in the air up to 1000 deg C is studied by the methods of thermogravimetry and IR-spectroscopy. It is shown that substance decomposition occurs in three steps and finishes at approximately 720 deg C with the formation of zirconium pyrophoshate and zirconium phosphate. Activation energy (Esub(a)103.4 kd/mol) and order (n=0.28) of decomposition reaction are determined

[en] Presented are the results of the kinetics study of alkali metal cation sorption (including cesium ones on amorphous zirconium phosphate and on zirconium phosphate specimens specifically formed by alkali metal cations). The ion-exchange sorption of alkali metal cations was effected from 0.1 N solutions of corresponding chlorides at strictly specified and controlled values of pH. Calculated were the activation energies E of alkali metal cation diffusion on investigated specimens. In sorption of alkali metal cations on amorphous zirconium phosphate, the effective diffusion coefficients vary in the order Cs⁺ approximately K⁺ > Na⁺ > Li⁺, whereas the corresponding activation energies vary in a reverse order

[en] The ion exchange properties of crystalline and amorphous phases of a sodium titanosilicate towards alkali and alkaline earth cations has been examined. Potentiometric titration of the crystalline phase in the proton form, H₂Ti₂O₃(SiO₄), showed that 80% of the sodium ion sites could be occupied to pH=12 and only 25% of the exchange sites could be filled by Cs⁺. However, when an equal concentration of Na⁺ was present in the Cs⁺ solution, the cesium loading was reduced to 5.6% (0.47meq/g) of the theoretical IEC. This loading is further reduced to less than 0.1 meq/g in solutions approximating the sodium content of nuclear waste solutions, i.e., 5-6 M NaNO₃, 1-3 M NaOH. This low capacity limits the usefulness of this exchanger to waste solutions less than 10^-5-10^-6 M in Cs⁺. The amorphous phase exhibits a very high affinity for Sr²⁺ but also for Ba²⁺ and Ca²⁺ in alkaline solution. These ions could serve as interferences for selective Sr²⁺ removal from nuclear waste solutions. Sodium titanium silicate has a tunnel structure. The low capacity of the exchanger for Cs⁺ stems form the fact that only a few of the exchange sites can be filled with Cs⁺ in the presence of Na⁺ and still maintain charge balance. 12 refs., 7 figs., 2 tabs