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Abstract  

Preliminary results of experimental testing and comparison of131I separation efficiency from model solutions on ion-exchange resins pretreated in some special ways are presented. Strongly basic and strongly acidic resins were pretreated chemically and used for the separation of radioiodine by means of isotopic-exchange, ion-exchange or chemisorption and their combinations. The sorbents were tested for pI, pH, their stability during storage and selectivity of separation. From the point of view of the efficiency and selectivity of separation the sorbents based on strongly basic resins and with assumed isotopic-exchange mechanism of radioiodine separation appear to be relatively more advantegeous.

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Abstract  

A great variety in retention properties occurs as a result of different methods of preparation of the sorbents. Specific surfaces and porosities, which are mostly connected with the sorption activities, may vary widely. The activation of Al2O3, SnO2 and silica gel, to produce highly active sorbents occurs only if the oxide is contacted with acid immediately after thermal treatment. The efficiency of the separation scheme has been tested using uranium and fission products under static conditions from strongly alkaline aqueous solutions.

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Abstract  

Vegetable tannin sorbent is evaluated as ion exchange resin using a multitracer study on the adsorption behavior of various elements. Lisiloma latisiliqua L. tannins, polycondensated into spherical pellets were chosen as sorbent resin material. Sorption evaluation of Ce, Cu(II), U(VI), Eu, Fe(III), Th, Nd as representatives of different classes of metal ions were done at different pH values. The distribution ratio of the studied elements was calculated from laboratory experiments. Tannic ion exchange material shows excellent ability for actinides and rare earth elements adsorption from waters. Using radiotracers, the number of catechins subunits involve in each tannin-metal complex was determined.

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Abstract  

The sorption of cesium ions from aqueous solutions on composite sorbents was investigated in static (by the batch method) and dynamic (on column) conditions. The composite sorbents consisted of copper hexacyanoferrate retained by an anion-exchange polymeric layer bound to porous silica beads. The influence of cesium concentration and solution flow rates on cesium sorption were studied. The cesium sorption isotherm obtained is of the Langmuir type. The shape of the breakthrough curves and the sorption capacity for cesium depend on the preparation procedure of the composites.

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Abstract  

Nuclear analytical techniques namely fission track technique using solid state nuclear track detector (SSNTD) and instrumental neutron activation analysis (INAA) have been standardized and applied for quantification of low uranium concentrations in liquid samples such as feed, elute and brine and solid sorbent samples respectively. The quantification of uranium is required for its recovery study from seawater, which is one of the potential sources of uranium. The uranium concentration of a liquid sample obtained by SSNTD method was compared with the other well established conventional techniques like ICP-MS, ICP-AES, adsorptive stripping voltametry and alpha spectrometry. INAA was applied for uranium concentration determination in the radiation grafted polyamidoxime sorbent samples.

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Abstract  

Properties and applications of composite ion exchangers developed in this Institute are described. The new sorbents consist of a selective inorganic ion exchanger, e.g., hexacyanoferrate of transition metals or hydrated antimony pentoxide, firmly incorporated into a resin matrix, e.g., phenol-formaldehyde, of various shapes. The composites have proved to be effective adsorbents for radionuclides of cesium, sodium, francium, elements 104 and 105, and some others. The sorbents were successfully tested as filter fillers for radiocesium removal from liquid radioactive wastes and from other solutions encountered in nuclear technology. They were also applied in radiochemical studies and in nuclear activation analysis.

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Abstract  

Various silica gel materials were chemically modified with imidazole, diaza-18-crown-6 (DA18C6) and dibenzod-18-crown-6 (DB18C6). The degree of functionalization of the covalently attached molecule was calculated from C, H, N analysis and ranged between 0.270 and 0.552 mmol/g (for sorbents with imidazole) and between 0.043 and 0.062 mmol/g (for sorbents with DA18C6 and DB18C6). The degree of functionalization depends on the reflux time and silica gel matrix used. Experimental sorption capacity ranged between 0.038 and 0.228 mmol/g (for sorbents with imidazole) and between 0.019 and 0.050 mmol/g (for sorbents with DA18C6 and DB18C6). Synthesized hexagonal mesoporous silica matrix MCM-41 with uniform pore diameter <40 Å was used too. Change of pore diameters of silica gel support to larger pores should have a positive influence on access of cobalt ion to sorption centers to increase of sorption capacity of sorbents. The sorption kinetics of cobalt and the influence of cobalt concentration, pH of various kinds of silica gel matrix with immobilized imidazole group in static conditions on sorption were measured. The sorption of cobalt in various conditions (pH, contact time of phases) with constant liquid-solid ratio (V/m = 50 ml/g) was studied. The distribution coefficients ranged between 200 and 50 000 ml/g (for imidazole), 85 and 120 ml/g (for DB18C6) and between 230 and 500 ml/g (for DA18C6) according to silica gel matrix used and according to the method of sorbent preparation. pH plays important role in the sorption of cobalt on prepared sorbents with immobilized crown ethers due to protonization of crown ethers. Protons significantly competes to sorption of cobalt in acidic solutions. The influence of presence of other heavy or toxic metals (Hg(II), Cd(II), Mn(II), Zn(II), Cu(II), Fe(III), Cr(III), Al(III) and the influence of sodium and potassium on sorption Co(II) from aqueous solutions was investigated. Sorption of cobalt decreases in order Hg > Cu > Cd > Zn, Fe > Mn > Al, Cr. The presence of sodium and potassium ions at concentration 0.05 mol/l significantly influences on the sorption of cobalt with sorbent with immobilized DB18C6 functional group.

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Abstract  

The uptake of several actinides [U(VI), Th(IV), Am(III), Cm(III)] and fission products was investigated from nitric acid solutions by two novel extraction chromatographic sorbents containing 2-(2-hexyloxy-ethyl)-N,N'-dimethyl-N,N'-dioctyl-malonamide (DMDOHEMA) and N,N,N',N'-tetraoctyl-3-oxapentane-1,5-diamide (TODGA), respectively. The kinetics of the uptake of actinides was studied. The sorption of metal ions fromz simulated Low Level Liquid Waste (LLLW) solutions was evaluated. The results of these experiments revealed that the actinides and lanthanides could be separated from the bulk of other fission products in simulated LLLW solutions on both sorbents.

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Abstract  

Three types of direct isotope dilution analysis (IDA) are mathematically treated: substoichiometric dilution analysis, the determination of sorbent capacity, and direct IDA with a constant amount of substance lost in the separation step. Tables and graphs are given for an easy determination of the amount of radioisotopeW 0 to be added and for the estimated error involved.

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Abstract  

The study is devoted to the characterization by both TG-DTG analysis and FTIR spectroscopy of beech flour, dyes and the sorbent-dyes products obtained through retention of the dyes from aqueous solution on the beech flour, to the aim of obtaining information on the nature of dyes’ retention, thermal behavior of the sorbent-dye materials as well as on their possible upgrading as fuel. Thermal analysis led to the conclusion that the mechanism of thermo-oxidative degradation is specific and the retention of dyes occurs on cellulose from beech flour. The nature of the bonds involved in dyes’ retention is also investigated by FTIR analysis, which evidences that dyes retention on cellulose is realized through hydrogen bonding between the NH and, respectively, OH groups from dye molecule and the oxygen atoms from cellulose. Involvement of the non-participating electrons of the nitrogen and, respectively, oxygen atoms of these groups in the extended electronic conjugation with aromatic nuclei strongly influences the capacity of the amino and, respectively, hydroxyl groups of forming hydrogen bonds, thus achieving dyes fixation on the sorbent. DTA analysis led to the conclusion that an improvement in the quality of the sorbent-dye materials as fuels is possible, as compared to untreated beach flour, as a result of the modification of the cellulosic fibers in the process of dyes retention.

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