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- Author or Editor: V. Kouřim x
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Improved inorganic ion-exchangers
III. Polyantimonic acid and mixed sulphate-silica gel systems
Abstract
A series of mixed sulphates of lead and calcium as well as the polyantimonic acid have been tested for their ability to isolate strontium from acidic solutions. The sol-gel method was used for preparation of particles with a silica gel matrix. Both polyantimonic acid and lead-calcium sulphate were found to be promising ion-exchangers.
Abstract
The synthesis of cyanoferrates of quadrivalent metals and the sorption of caesium ions by these materials have been studied. It has been found that the compositions of the compounds and their properties are strongly influenced by the degree of hydrolysis of the metal. These is no sorption of caesium by Zr4+ and Th4+ cyanoferrates, while the compounds of oxygencontaining bivalent complex cations exhibit behaviour similar to that of the other bivalent metals. The sorption of caesium by (TiO)2R is govermed by an ion-exchange mechanism; with (ZrO)2R changes occur in the crystal lattice, and (ThO)2R exhibits a low affinity towards caesium.
Affinities of insoluble hexacyanoferrates(II) for alkali metals and ammonium
II. Hexacyanoferrates(II) of bivalent manganese, iron and cadmium
Abstract
The affinities of insoluble ferrocyanides of bivalent manganese, iron and cadmium for sodium potassium, rubidium, caesium and ammonium have been studied. It has been found that the affinities of the univalent cations for the ferrocyanides generally increase in the usual order Na<K<NH4<Rb<Cs. Comparing the results with those previously obtained, the affinity towards formation of double ferrocyanides with univalent cations generally follows the order Cd ∼ Mn >Co>Fe(II)>Ni>Zn>Cu>Fe(III). The precipitation isotherms of the systems are presented and the relationship between the affinities and some other properties of the transition metal ferrocyanides is discussed.
Improved inorganic ion-exchangers
I. Systems with organic polymers as binding materials
Abstract
The use of organic polymers as binding agents for inorganic ion-exchangers has been studied. Poly-vinyl acetate and polystyrene polymers were applied to ammonium phosphomolybdate and zinc ferrocyanide. The method of preparation and hydromechanical properties of the resulting materials in ion-exchange columns are described. The materials were used for caesium removal from simulated Purex high-level radioactive waste solutions. The break-though capacities and results of repeated sorption-elution cycles are presented.
Improved inorganic ion-exchangers
II. Ammonium molybdophosphate—Silica gel system
Abstract
The possibility of using the sol-gel method for preparation of inorganic ion-exchangers with a silica gel matrix has been demonstrated on the ammonium molybdophosphate-silica gel (AMP-SG) system. For the preparation of the ion-exchanger a sodium silicate solution, containing AMP and components to cause gelling to silica gel after increase of the temperature of the solution, is poured into a hot stirred silicone oil. The solution forms droplets, which are filtered off after their gelling, washed and dried. Beads containing 65 wt.% of AMP per gram of dry material have been prepared by this method and tested in ion-exchange columns for caesium removal from nitric acid solutions. Caesium may easily be desorbed with ammonium chloride or nitrate solutions. The ion-exchanger is suitable for long-time reversible column operation, having not only good chemical, thermal and radiation stabilities but also good mechanical and hydrodynamic properties and resistance to abrasion. It combines the advantage of the good kinetics of ion-exchange obtained with microparticles of precipitated inorganic ion-exchanger, with the low flow resistance of large particles.
Abstract
The process of incorporation of radioactive wastes into a suitable matrix to form a stable product for long term disposal has been studied. The changes, occuring during the thermal treatment with glassy materials, i.e. drying, transformation processes, sintering, melting, etc. have been followed using emanation (radon) thermal analysis. This method was found useful in solving the problems of process development.
