Authors:A. Rodríguez, B. López, A. Baca, and C. Gutiérrez
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.
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.
Authors:J. Santana, L. Lima, J. Torres, F. Martínez, and S. Olivares
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.
Authors:T. Prasad, P. Kalsi, R. Acharya, V. Manchanda, and P. Tewari
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.
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.
Authors:V. Baran, R. Caletka, M. Tympl, and V. Urbánek
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.
Authors:S. Milonji, I. Bispo, M. Fedoroff, C. Loos-Neskovic, and C. Vidal-Madjar
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.
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.
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 radioisotopeW0 to be added and for the estimated error involved.
The inorganic sorbent potassium cobalt(II) hexacyanoferrate(II) was tested for removal of radiocesium from alkaline salt solutions that are typical of intermediate level radioactive wastes generated at spent fuel reprocessing plants in India. Excellent results were obtained both in batch equilibration and column operation.