Composite absorbers of inorganic ion-exchangers and polyacrylonitrile binding matrix

Maximum attainable self-absorption dose for cemented composite ion-exchanger, consisting of nickel hexacyanoferrate and polyacrylonitrile binding matrix, loaded with¹³⁷Cs up to repository acceptable level (1.1·10¹² Bq·m^–3) was calculated to be 10⁵ Gy. The cemented absorber with sorbed caesium was irradiated by⁶⁰Co source up to 1 MGy, and leach tests were performed to determine possible influence of self-irradiation on the caesium leachability. No radiation induced changes in caesium immobilisation in solidified ion-exchanger were observed.     

Composite absorbers consisting of inorganic ion-exchangers and polyacrylonitrile binding matrix

Both cementation and vitrification was shown by preliminary experiments to be applicable for treatment of the spent composite absorbers with polyacrylonitrile binding matrix for final disposal. Loadings of cement mix with composite absorbers up to 5–9% (w/w) were achieved Admixtures of natural clinoptilolite were found to improve compressive strength of the samples. The presence of PAN binding polymer was found not to disqualify the composite absorber tested from final treatment by vitrification.     

Improved inorganic ion-exchangers

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.     

Improved inorganic ion-exchangers

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.     

Uses of liquid ion-exchangers in inorganic analysis

A review of recent uses of liquid ion-exchangers in inorganic analysis is presented.     

Investigations on some inorganic ion-exchangers after irradiation

The changes in the ion exchange properties of crystalline zirconium phosphate, cerium phosphate and cerium arsenate after irradiation have been investigated. The absorbed gamma dose was 10⁹ rad in all cases, the experiments were carried out before and immediately after irradiation with the same samples. Besides the investigations of structural change, the ion exchange behaviour of the above mentioned materials was studied in detail. The ion exchange capacities were determined using a tracer technique for the alkali metal ions, and some relations between ion exchange and structure were revealed.     

Sorption of radionuclides on inorganic sorbents

Inorganic sorbents are often used in separation of metals and radionuclides in radioanalytical application and they were also used in technological scale for separation of radionuclides in cleanup of Three Mile Island NPP. Inorganic sorbents become popular in the last years because no problem with organic contamination, there are stable against radiation, sorption efficiency can be tailor made for selective separation of chosen metal. Contrary to the organic sorbents they have usually lower capacity and chemical stability is limited to narrower pH. Nevertheless of some problems, many good properties of inorganic sorbents make them very attractive for sorption study.     

137Cs sorption on granular inorganic ion-exchangers based on titanium and zirconium hydroxophosphates

We have studied the sorption properties of some granular inorganic ion-exchangers synthesized by gel technology, such as titanium and zirconium hydroxophosphates (THP, ZHP), titanium and zirconium molybdophosphates and titanium and zirconium phosphate-ferrocyanides. A high selectivity of THP and ZHP modified with ferrocyanide and molybdate ions to¹³⁷Cs has been found. The possibility of applying inorganic sorbents for the purification of cesium-137 contaminated foodstuff is illustrated on the examples of fish treatment.     

Research and application of inorganic selective sorbents at Mayak PA

This work has been performed in order to identify selective inorganic sorbents for caesium and strontium. Thin-layer sorbents with nickel ferrocyanide embedded in an inert matrix were found to be the best for caesium. Sorbents including non-stoichiometric manganese dioxide were selected for strontium. Bench tests have been carried out on the purification of desalted water of SNF storage-pool from ¹³⁷Cs, and on the purification of contaminated natural water from ⁹⁰Sr. The facility for synthesizing the ferrocyanide sorbent with the registered mark ‘Seleks-CFN’ has been brought into operation. The sorbent ISM-S seems promising for ⁹⁰Sr decontamination. To cite this article: M.V. Logunov et al., C. R. Chimie 7 (2004).

Résumé

Recherches et applications sur l’utilisation de sorbants spécifiques à Mayak. Des sorbants sélectifs du césium et du strontium ont été identifiés. Pour le césium, le meilleur s’avère être le ferrocyanure de nickel, s’il est utilisé sous forme de couche mince. Pour le strontium, on a sélectionné des composés non stœchiométriques de dioxyde de manganèse. On a mené des tests visant à épurer en césium l’eau des piscines d’entreposage des combustibles nucléaires usagés, et en strontium des eaux contaminées. Une installation industrielle permettant de préparer le sorbant à base de ferrocyanure de marque « Seleks-CFN » a été réalisée. Le sorbant ISM-S semble prometteur pour la décontamination en strontium. Pour citer cet article : M.V. Logunov et al., C. R. Chimie 7 (2004).     

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.     

Sorption of Hf, Zr and Nb on organic and inorganic ion-exchangers from mineral acids solutions

Sorption coefficients of Hf, Zr and Nb on nickel-potassium hexacyanoferrate(II) (NF), nickel hexacyanoferrate(II) composite ion exchanger (NCF) and on the ion exchange resins (Dowex-1 and Dowex-50) from inorganic acids solutions were determined. The results obtained indicate that hafnium, zirconium and niobium in dilute sulphuric and hydrochloric acids form anionic and cationic complexes which sorbed on the ion exchangers studied.     

Composite precursor of polyacrylonitrile with hydrolytic lignin

Composite precursor based on hydrolytic lignin and polyacrylonitrile was obtained and fibrous composite materials were formed at 80: 20 to 40: 60 ratios between the starting components. A probable mechanism is suggested by which products of cocarbonization of lignin and polyacrylonitrile are formed, with 80–90 wt % carbonized residue produced in an inert atmosphere.     

Sorption of arsenic onto inorganic sorbents modified with iron compounds

Granulated inorganic sorbents based on silica gel of KSKG grade and aluminum oxide and modified with Fe(III) compounds were developed for water treatment to remove As(V). The influence of the particle size of the modifying additive on the ability of silica gel to take up As(V) was examined. The KSKG-based sorbents modified with nanoparticles of Fe(III) compounds exhibit the highest sorption capacity. The capacity of silica gel based sorbents modified with nanoparticles of iron compounds for As(V) is higher than that of analogous sorbents modified with iron oxides prepared by thermal decomposition of Fe(III) nitrate.     

Composite cellulose-inorganic sorbents for 137Cs recovery

In this study, cellulose-inorganic sorbents based on bleached cotton fibres and ferrocyanides of different d-metals have been prepared and used for separation of ¹³⁷Cs from simulated aqueous solutions. Comparative analysis has been carried out of the sorption properties of obtained sorption materials towards to micro- and macroquantities of caesium at different liquid to solid phases ratios. Various characterization methods including X-ray analysis, IR spectroscopy, and differential thermal analysis were used to determine the structural properties of the obtained composite sorbents. It has been confirmed that the sorbents obtained at approximately the same content of the inorganic component are characterized by different values of the recovery rate and ¹³⁷Cs distribution coefficient.     

Application of the sol-gel method for the preparation of some inorganic ion-exchangers in spherical form

Starting from the principles of sol-gel method, developed originally for the preparation of nuclear fuels in spherical form, their application to the preparation of microspheres of various non-nuclear elements is presented. In addition to the preparative conditions of the primarily hydroxidic spheres, their conversion into other insoluble compounds such as phosphates, ferrocyanides, sulphides, etc. is described. These sol-gel products work very well as ion-exchangers; their sorption properties are quite comparable to those of the common powder sorbents, the sphere from being their main beauty. Applicability of these sorbents as well as their limitations are also discussed.     

The behavior of Ba and Sr on inorganic and organic ion-exchangers from sulphuric acid solutions Preliminary experiments

The ion-exchange behavior of Ba and Sr on nickel-potassium hexacyanoferrate(II) (NiNF), cobalt-potassium hexacyanoferrate(II) (CoNF), cupric-potassium hexacyanoferrate(II) (CuNF) , zinc-potassium hexacyanoferrate(II) (ZnNF) and the ion exchange resin Dowex-50 has been studied in sulphuric acid solutions. 0.05M H₂SO₄ was used for continuous on-line separation of short-lived Ba and Sr isotopes produced at the M-25 at FLNR microtron, JINR, Dubna. The radionuclide of Ba was sorbed strongly on NiNF, CoNF, CuNF, ZnNF and on Dowex-50 while Sr was sorbed very well on Dowex-50.     

Uptake of inorganic acids on hydrogels of tetravalent hydroxides and its application for the preparation of some inorganic sorbents

The paper deals with the study of inorganic acid uptake on hydrogels of titanium, zirconium, and tin hydroxides prepared by the sol-gel method in the form of regular spherical particles. The aim of the work was the determination of the basic conditions for the preparation of inorganic ion exchangers by means of the conversion of the hydroxide gel. The results obtained prove that the exchange of hydroxide groups of the gel phase for the respective anions plays the decisive role in the uptake on zirconium hydroxide. With similar titanium and tin compounds, the main process affecting the uptake is the formation of adsorption compounds and the free diffusion of the electrolyte into the gel phase. The possibilities of the application of the sol-gel method for the preparation of inorganic sorbents are discussed.     

Composite sorbents based on synthetic manganese oxide and carbon fiber

Manganese oxides have been prepared on the surface of carbon fiber by simple methods: coprecipitation of manganese salts of different valence in the presence of fiber as a support or electrodeposition from Mn(II) salt solution on a carbon fiber cathode, in the presence of chitosan including, under oxidation with air oxygen conditions. The obtained samples have been characterized by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Sorption properties of the composites toward As(V) have been studied. The relationships between sorption properties, structure, Mn valence, and manganese oxide surface morphology have been discussed.     

Fr and Ra fixation on some inorganic sorbents or mixed composite ion exchangers

Zinc and nickel hexacyanoferrates (II) present a high affinity for²²³Fr and no retention for²²³Ra in hydrochloric acid solutions with concentrations greater than 0.5N. Hydrated antimony pentoxide is the best sorbent for²²³Ra. Incorporated in a composite exchanger, it could be used for decontamination purposes.