The phase composition of the powder synthesized from aqueous solutions of sodium silicate Na2SiO3 and iron sulfate FeSO4 at the molar ratio Fe/Si = 2, as determined by x-ray diffraction (XRD) data, included hydrated sodium iron sulfate Na2Fe(SO4)2 · 4H2O and an x-ray amorphous product based on hydrated iron and silicon oxides. The phase composition of the powder obtained by fourfold washing of the synthesized powder in distilled water was represented by an x-ray amorphous product. Following firing in the air at temperatures ranging from 400 to 1200°C, hematite (Fe2O3) and cristobalite (SiO2) were identified in powder samples and the corresponding ceramics. Following firing at 900°C in graphite powder bedding, the phase composition of ceramic samples included magnetite (Fe3O4), laihunite (Fe4.74(SiO4)3), and fayalite (Fe2SiO4). The powder prepared from the product isolated from the mother liquor included hydrated sodium iron sulfate, Na2Fe(SO4)2 · 4H2O, and sodium iron sulfate hydroxide hydrate (metasideronatrite), Na4Fe2(SO4)4(OH)2 · 3H2O. Following heat treatment at 400°C, sodium iron sulfate (Na3Fe(SO4)3) was identified as the predominant phase in the powder. Powders resulting from the interaction of aqueous solutions of sodium silicate and iron sulfate can be used in the manufacture of high-temperature dyes and materials with magnetic properties, the creation of analogs of lunar or Martian regolith, as well as the development of functional (cathode) materials for Na-ion batteries.

Powders of hydroxyapatite (HA) Ca10(PO4)6(OH)2 treated in 0.25M aqueous solutions of ammonium NH4H2PO4, sodium NaH2PO4 and potassium KH2PO4 dihydrophosphates for 1 hour under stirring were used for ceramics production. According to the XRD data, there was no changes in the phase composition of the powders after such treatment. After firing in the range of 900 – 1100 ?С, the phase composition of ceramics based on HA Ca10(PO4)6(OH)2 powder treated with an aqueous solution of NH4H2PO4 included ?-tricalcium phosphate ?-Ca3(PO4)2 and HA Ca10(PO4)6(OH)2; The phase composition of ceramics based on HA Ca10(PO4)6(OH)2 powder treated with NaH2PO4 aqueous solution included sodium-substituted tricalcium phosphate Ca10Na(PO4)7 and HA Ca10(PO4)6(OH)2; the phase composition of ceramics based on HA Ca10(PO4)6(OH)2 powder treated with an aqueous solution of KH2PO4 included potassium-substituted tricalcium phosphate Ca10K(PO4)7 and HA Ca10(PO4)6(OH)2. The formation of biphasic ceramics occurred due to a decrease in the molar ratio Ca/P of HA powder after treatment in aqueous solutions of ammonium NH4H2PO4, sodium NaH2PO4 and potassium KH2PO4 dihydrophosphates. HA-particle surface adsorption of cations and anions from the solution, slight dissolution of HA in solutions of dihydrophosphates with acidic pH, as well as ion exchange of cations and anions of HA for cations and anions from solutions, were possible processes providing change in the ratio of cations and anions in the HA powder. The resulting ceramic composites contain biocompatible phases, and can be recommended for the creation of bone implants.

The development of natural hydro-mineral raw materials for the isolation of lithium is complicated by its separation and purification from the accompanying compounds of sodium, magnesium, calcium and other substances. Mixed solutions are also formed during the regeneration of lithium from various used products. Ion exchange is often used as a solution to such problems. However, in traditional ion-exchange processes it is necessary to use auxiliary reagents for their regeneration. In the present study, we considered the possibility of using the reagentless two-temperature ion exchange method for purification of lithium from ions of the first and second groups. A scheme of reagentless purification of 1 N LiCl solution from CaCl2 and KCl impurities was proposed and experimentally confirmed. This scheme includes successive operations of two-temperature ion-exchange purification from CaCl2 by the parametric pumping method using polymethacrylic cation exchanger and subsequent two-temperature ion-exchange purification from KCl by the parametric pumping on synthetic zeolite A. The differential enthalpy value of exchange of calcium ions for lithium ion from a solution containing 1.0 N LiCl – 0.020 N KCl – 0.01 N CaCl2, amounting to 7.7 kJ/g-eq, was determined. It was shown that with increasing temperature, the selectivity of the exchange of lithium and potassium ions on zeolites A and X decreases significantly. This effect is characterized by high values of the differential exchange enthalpy ~ -20 kJ/g-eq.

Hydroxyapatite (HA) Ca 10 (PO 4 ) 6 (OH) 2 powders kept for 1 h with stirring in 0.25 M aqueous solutions of dihydrogen phosphates of ammonium NH 4 H 2 PO 4 , sodium NaH 2 PO 4 , and potassium KH 2 PO 4 were used to obtain ceramics. According to XRD data, there were no changes in the phase compositions of powders after such treatment. After firing at 900 – 1100°C the phase composition of ceramics based on HA Ca 10 (PO 4 ) 6 (OH) 2 powder treated with an aqueous solution of NH 4 H 2 PO 4 included β-tricalcium phosphate β-Ca 3 (PO 4 ) 2 and HA Ca 10 (PO 4 ) 6 (OH) 2 ; the phase composition of ceramics based on HA powder Ca 10 (PO 4 ) 6 (OH) 2 treated with an aqueous solution of NaH 2 PO 4 included sodium-substituted tricalcium phosphate Ca 10 Na(PO 4 ) 7 and HA Ca 10 (PO 4 ) 6 (OH) 2 ; the phase composition of ceramics based on HA powder Ca 10 (PO 4 ) 6 (OH) 2 treated with an aqueous solution of KH 2 PO 4 included potassium-substituted tricalcium phosphate Ca 10 K(PO 4 ) 7 and HA Ca 10 (PO 4 ) 6 (OH) 2 . The formation of biphasic ceramics occurred because of reduction in the Ca/P molar ratio of HA Ca 10 (PO 4 ) 6 (OH) 2 powder after treatment in aqueous solutions of dihydrogen phosphates of ammonium NH 4 H 2 PO 4 , sodium NaH 2 PO 4 , and potassium KH 2 PO 4 . Adsorption of cations and anions from solutions on the surface of HA particles, slight dissolution of HA in aqueous solutions of dihydrogen phosphates with acidic pH, as well as ion exchange of cations and anions in the HA structure for cations and anions from solutions were possible processes effecting change in the ratio of cations and anions in HA powder. The resulting ceramic composites contain biocompatible phases and can be recommended for creating bone implants.

Double calcium’ammonium pyrophosphate monohydrate Ca(NH 4 ) 2 P 2 O 7 •H 2 O was synthesized as a result of the interaction of calcium carbonate, an aqueous solution containing pyrophosphoric and lactic acids, and ammonia. The synthesized powder turned black after the thermal treatment in a range of 500—700 °C due to amorphous carbon, which is a product of the destruction of the organic nature components present in the prepared powder. After the thermal treatment at 500 °C, the powder is amorphous to X-rays. The phase composition of the powder after the thermal treatment at 600 °C is presented by β-calcium polyphosphate β-Са(PO 3 ) 2 , while β-calcium polyphosphate β-Ca(PO 3 ) 2 and tromelite Ca 4 P 6 О 19 are observed after the thermal treatment at 700 °C. The calcium phosphate powder colored due to presence of amorphous carbon can be used as a photocured suspension component that increases the resolution in stereolithographic printing of pre-ceramic semifinished products with a specified geometry of the pore space of calcium phosphate ceramic matrices. The synthesized powder of double calcium’ammonium pyrophosphate monohydrate Ca(NH 4 ) 2 P 2 O 7 •H 2 O can be applied as a precursor of biocompatible phases for the fabrication of calcium phosphate ceramics used in medicine for the treatment of bone tissue defects.

Double calcium’ammonium pyrophosphate monohydrate Ca(NH4)2P2O7•H2O was synthesized as a result of the interaction of calcium carbonate, an aqueous solution containing pyrophosphoric and lactic acids, and ammonia. The synthesized powder turned black after the thermal treatment in a range of 500—700 °C due to amorphous carbon, which is a product of the destruction of the organic nature components present in the prepared powder. After the thermal treatment at 500 °C, the powder is amorphous to X-rays. The phase composition of the powder after the thermal treatment at 600 °C is presented by β-calcium polyphosphate β-Са(PO3)2, while β-calcium polyphosphate β-Ca(PO3)2 and tromelite Ca4P6О19 are observed after the thermal treatment at 700 °C. The calcium phosphate powder colored due to presence of amorphous carbon can be used as a photocured suspension component that increases the resolution in stereolithographic printing of pre-ceramic semifinished products with a specified geometry of the pore space of calcium phosphate ceramic matrices. The synthesized powder of double calcium’ammonium pyrophosphate monohydrate Ca(NH4)2P2O7•H2O can be applied as a precursor of biocompatible phases for the fabrication of calcium phosphate ceramics used in medicine for the treatment of bone tissue defects.

The effect of temperature on the exchange of di- and monovalent ions on polymethacrylic and polyacrylic cation exchangers in the range from 298 to 413 K is studied. It is shown that the differential enthalpy and the equilibrium coefficient simultaneously increase with temperature. The dependences of the enthalpy on temperature are linear. The effect of temperature on the enthalpy of ion exchange observed for all studied ion exchangers is much more strong than in the systems described in the literature with sulfonic acid cation exchangers and highly basic anion exchangers. The problem of taking into account the dependence of enthalpy on temperature when predicting the behavior of ion-exchange systems is discussed.

For the development of methods for the disposal of radioactive waste in the rocks of the earths crust, the concept of phase and chemical correspondence in the system of matrix material ― host rock has been proposed. This principle allows directional synthesis of certain mineral matrices. Matrix materials were experimentally synthesized ― solid solutions of minerals for immobilization of alkaline, alkaline-earth, rare-earth elements ― radionuclides. The properties of a number of solid solutions of minerals are investigated. The possibilities of processing graphite into stable matrices are studied. Methods of fixation and separation of noble metals (components of radioactive waste) and halides (Br, I) have been developed. The problems of processing glass matrix minerals (borosilicate and aluminophosphate glasses) into stable crystalline matrix materials are considered. Methods for processing glass matrices into mineral matrix materials are presented.

Изучено влияние температуры на селективность и энтальпию обмена ионов Ni2+ − Na+ и Mg2+− Na+ на полиметакриловом катионите КБ-4П2 в интервале от 298 до 413 К. Показано, что при повышении температуры одновременно со значительным увеличением селективности к двухзарядному иону линейно увеличивается дифференциальная энтальпия. Наиболее сильно селективность возрастает в области «перегретых» растворов с температурой выше 373 К. Влияние ионного состава ионита на дифференциальную энтальпию значительно меньше, чем влияние температуры.

The problem of experimental determination of the differential enthalpy of ion exchange is considered. The determination of the enthalpy from experimental equilibrium coefficients is characterized by a high degree of error. A considerably more accurate method of determination of the differential enthalpy of ion exchange on selective ion exchangers is proposed. The method is based on the analysis only of the composition of the solution in the equilibrium system at two temperatures. The influence of temperature on the exchange of mono- and divalent ions on polyacrylic and polymethacrylic cation exchangers within the range from 273K to 400K is studied. It is shown than for all exchangers under study the differential enthalpy linearly increases with temperature. The role of the increase of ΔHn¯ with temperature in the process of a single-step dual-temperature separation is estimated. It is found that the increase of the upper temperature boundary leads to a very sharp increase of the degree of dual-temperature separation. This effect is most pronounced in superheated solutions. It is shown that when predicting changes in selectivity with temperature and the extent of purification of solutions of alkali metal salts from admixtures of divalent ions, it is necessary to take the temperature dependence of the ion exchange enthalpy into account.

We compare the ion exchange selectivity of phenol-type sorbents based on phenol formaldehyde resins, products of condensation of diatomic phenols with formaldehyde, and crosslinked polymer based on C-phenyl[4]resorcinarene resin, for cesium and rubidium ions. It is shown that phenol formaldehyde sorbents are the ones most selective. The interaction of alkali metal cations with the anion of calix[4]arene is investigated via quantum-chemical modeling. It is shown that the selectivity toward cesium and rubidium ions in ion exchangers of the phenolic type is not due to specific interactions of ions with phenolic groups.

It is shown that at a temperature of 295 K, phenol groups of phenol formaldehyde sorbents are characterized by the value pK ∼ 13.0–13.7. It is found that raising the temperature to 343 K reduces the pK value by one. It is concluded that the reason for the lower acidity of phenol formaldehyde sorbents relative to phenol in an aqueous solution is the smaller amount of firmly bound water.

It is shown that ion-exchange sorbents based on phenol-formaldehyde resins can be used for a long time for isolating and separating rare alkali metals without any significant changes in the ion-exchange selectivity and capacity. When the phenol sorbents were used in alkaline solutions at elevated temperatures, carboxyl groups gradually accumulated in them as a result of the oxidation of methylol groups with oxygen dissolved in the solution. This led to a considerable increase in the ion-exchange capacity of the sorbents and a simultaneous decrease in the selectivity with respect to Cs + -Rb + and Rb + -K + ions (it is desirable to avoid the drying of phenol ionites in air by storing them in a swelled state in closed vessels).

Temperature was shown to substantially influence the swelling of KB-2e3 polyacrylic and KB-4P2 polymethacrylic ionites cross-linked by triethylene glycol dimethacrylate (TEGDM) and divinylbenzene (DVB). Maximum swelling changes as the temperature increased were observed for the Ca form of the KB-4P2 ionite. Swelling and contraction of polymethacrylic cationite grains as the temperature decreased and increased occurred at equal fairly high rates, whereas the sorption of water by the polyacrylic cationite in the calcium form cross-linked by TEGDM occurred much more slowly than desorption.

A new method of dual-temperature concentration and purification of pure and mixed solutions of calcium, magnesium, and sodium chlorides without solvent vaporization and the use of auxiliary reagents was studied. The method was based on the influence of temperature on the swelling of polymethacrylic and polyacrylic ionites. It was continuous solution passage through a column with a cationite with periodic temperature changes. A substantial increase in the concentration of solutions occurred at the “cold” stage of the process, and a decrease in concentration was observed at the “hot” stage.

The new phenomenon of a two-temperature non-reagent concentration of alkali solutions on sorbents based on the phenol-formaldehyde resin Amberlit XAD 761, PFR-1.4/0.7, and sulfonated phenol-formaldehyde ionite KU-1 was investigated. It was found that during an alkali solution’s passage through a column with a sorbent and a periodical change in temperature in the “cold” stage, the concentration of alkali in the filtrate appeared to decrease, while in the “hot” stage, the alkali concentration appeared to increase. It was shown that the increase in alkali concentration in a solution in contact with phenol-formaldehyde resin is determined by the ion-exchange properties of the phenol groups, and is associated with an increase in water dissociation upon a rise in temperature.