Extraction chromatography of thorium ion by solid phase impregnated resins containing bi-functional organic extractants</p> </p>

Summary Macroporous methyl methacrylate polymeric resin (XAD-7) was investigated incorporating both acidic organophosphorous extractant (cyanex-301) and one neutral extractant from the followings: dibenzo 18 crown 6 (DB18C6), 18 crown 6 (18C6) and 15 crown 5 (15C5). The sorption behavior of the solvent impregnated resin (SIR) towards thorium ion, including batch equilibrium, and kinetic operation are described. Different factors affecting the uptake of metal ions and hence, the separation efficiency of the impregnated resins were investigated. The maximum uptakes of Th⁴⁺ were found to be 62.9, 66.7 and 92.6% for DB18C6, 18C6 and 15C5, respectively. Synergistic extraction of various CE towards thorium ion was tested with cyanex-301 to enhance the sorption capacity as well as the selective separation efficiency. A relatively high capacity of the chelating resin towards tetravalent thorium was found. The capacities of the co-impregnated resins were found to be 2.11, 2.42 and 3.85 mmol/g for DB18C6, 18C6 and 15C5, respectively. The impregnated resin containing cyanex-301 and 15C5 can be utilized for selective separation and pre-concentration of thorium ion from nitrate medium in the presence of several interfering metal ions.</p> </p>     

Cation-exchange separation of uranium from thorium in nitric acid medium</p> </p>

Summary Sorption behavior of Th and U on cation-exchange resins was investigated from nitric acid medium by both batch and column methods. The cation-exchange studies involved the sorption of UO₂²⁺ and Th⁴⁺ and their cationic complexes onto Dowex 50Wx8 and Dowex 50Wx4 resins (50-100 mesh). The batch data yielded a separation factor (K_d,Th/K_d,U) value of >100 for the cation-exchanger, Dowex 50Wx4 at 1-2M HNO₃. Separation of uranium from thorium was also carried out by column method in nitric acid medium using cation-exchangers, Dowex 50Wx4 as well as Dowex 50Wx8. While uranium elution was possible at 1M HNO₃, Th could be eluted only at higher concentration of nitric acid (>6M). The stripped solution emanating from a mixer settler employing di-2-ethyl hexyl isobutyramide as extractant and feed solution similar to THOREX process comprising 350 mg/l U and 380 mg/l Th in 0.75M HNO₃ was loaded on the column and the decontamination factor value for U in the product was >1000.</p> </p>     

Cs and Sr removal from solution using potassium nickel hexacyanoferrate impregnated zeolites</p> </p>

Summary Potassium nickel hexacyanoferrate, KNiFC, was incorporated in the porous matrix of zeolites by successive impregnation with Ni(NO₃)₂ and</o:p></p> K₄Fe (CN)₆.¹ CFC and PFC exchangers were first prepared by impregnating the potassium nickel hexacyanoferrate into the clinoptilolite and the synthetic P zeolite, respectively. Ion-exchange isotherms and breakthrough curves were plotted. Results showed that the CFC sorbent is suitable for removal of Cs⁺ where PFC is more suitable for Sr²⁺. Negative effect of Na⁺ as a competing ion in these exchangers was less than in the parent zeolites. Isotherm plots fitted the Langmuir equation.</p> </p>     

Preconcentration of 198Au in a green alga, Rhizoclonium</p> </p>

Summary The bioaccumulation of ¹⁹⁸Au radionuclide, by Rhizoclonium riparium a member of Chlorophyceae has been studied. It has been observed that accumulation of gold on Rhizoclonium is almost pH independent and slightly higher at basic pH. Accumulation of gold was studied with ¹⁹⁸Au radiotracer, 0.1, 1 and 5 ppm concentrations of gold. It has been concluded from the biochemical analysis that the gold accumulation is due to adsorption in the cellulose and not in protein, fat and carbohydrate. Accumulated gold was recovered when washed with conc. HNO₃.</p> </p>     

Sorption of Co, Cs, Sr and I onto argillaceous rock as studied by radiotracers</p> </p>

Summary Sorption of⁶⁰Co,⁸⁵Sr, 137Cs and¹²⁵I have been studied on samples originated from Boda (siltstone-) claystone formation (BCF) (Hungary). The distribution of K_dvalues have been determined in static batch experiments using natural groundwater. The order of sorption of isotopes was Co>Cs>Sr>I, where iodine exhibits sorption properties in a modest extent. The sorption isotherm was determined for Cs from measurements carried out in 10^-5-10^-1M initial concentration range. The isotherm can be described with non-linear Freundlich approximation in the range of</o:p></p> 10^-7-10^-4M equilibrium concentration. At concentrations >10^-2M the isotherm achieves saturation. Hence, it is suggested that sorption of Cs on BCF is dominated by cation-exchange reactions on the illite mineral component. In the case of Co and Sr, precipitation reactions occurred during the experiments performed with carrier-containing solutions. This can be attributed to the low values of solubility product constants of SrCO₃, SrSO₄and Co(OH)₂, formed from anions present in the natural groundwater.</p> </p>     

Thermodynamic modeling for the removal of Cs+, Sr2+, Ca2+and Mg2+ions from aqueous waste solutions using zeolite A</p> </p>

Summary The batch removal ofCs⁺, Sr²⁺, Ca²⁺and Mg²⁺ions from aqueous solutions using synthetic zeolite A was investigated. The influence of the initial ion concentration, pH and temperature was studied. The obtained isotherm data have been correlated with Langumir, Freundlich, and Dubinin-Radushkevich(D-R) isotherm models. The effect of the temperature on the equilibrium distribution values has been utilized to evaluate the standard thermodynamic parameters such as free energy (DG), enthalpy (DH) and entropy (DS). Based on the D-R isotherm expression, the maximum ion-exchange capacity and the mean free energy of each studied ion has been determined. The selectivity sequence, deduced from the equilibrium isotherm data is: Sr²⁺>Ca²⁺>Mg²⁺>Cs⁺>Na⁺.</p> </p>     

Recovery of technetium adsorbed on charcoal</p> </p>

Two methods capable of near complete recovery of technetium adsorbed on charcoal are presented. The first involves liquid extraction of the technetium from the charcoal by hot 4M nitric acid. An average recovery of 98% (n=3) is obtained after three rounds of extraction. The second method involves dry ashing with air in a quartz combustion tube at 400-450 °C. This method yields an average recovery of 96% (n=5). Other thermal methods were attempted, but resulted in reduced recovery and incomplete material balance.</p> </p>     

Selective separation of uranium using trimethylammonium acetosalycoylhydrazone modified Duolite C20 resin</p> </p>

Summary Duolite C20 resin modified with trimethylammonium acetosalycoylhydrazone has been developed, for the selective separation and/or preconcentration of uranium. The modified resin was characterized by elemental analysis and infrared spectra. Batch and column modes were applied. The newly designed resin quantitatively sorbs uranium ion at pH 3 when the flow rate equals to 2 ml ^. min ^-1 . The sorption capacity was 0.750 mmol ^. g^-1 for uranium ion, whereas its preconcentration factor was 200. The lower limit of detection was 5 ng ^. ml^-1 and its desorption was effective with 5 ml of 3 mol ^. l^-1 HCl or HNO₃ prior to detection spectrophotometry. The modified resin was highly ion-selective in nature even in the presence of large concentrations of electrolyte or organic media, with a preconcentrating ability for uranium ion. The modified resin was tested on its utility with synthetic, real and certified ore samples, showed RSD values of <2% reflecting the accuracy and reproducibility of the newly modified resin.</p> </p>     

Removal of uranyl ions from wastewaters using cellulose and modified cellulose materials</p> </p>

Summary Three silylcellulosic derivatives with different substitution degree were examined as sorbents for uranyl ions. The adsorption rate and capacity of cellulose and modified cellulose were investigated in aqueous media, at various pH and temperature values. The polymer - metal complexes of UO₂²⁺ were characterized by infrared and electronic spectra, and thermogravimetry. The thermal behavior of cellulose (C), trimethylsilyl - cellulose (tmsc, SD= 2.85) and triphenylsilyl - cellulose (TPSC1, SD=2.89 and TPSC2, SD =2.70) and their complexes with uranyl ions in atmospheric air has been studied between room temperature and 600 °C. The Coats-Redfern method was applied to estimate the kinetic parameters. The results revealed that the complexation of C and TMSC with UO₂²⁺ increases the thermal stability.</p> </p>     

Sorption and desorption of UO2 2+, Th4+ and Ru3+ on the synthetic analogue of muscovite</p> </p>

Summary Sorption and desorption of UO₂²⁺, Th⁴⁺ and Ru³⁺ on the synthetic analogue of the mica mineral muscovite has been studied by a batch technique. The synthesized gel was characterized by XRD, EDXRFS, FTIR, TGA and SEM and was found to have a composition K_1.4Al_4.2(Si₆Al₂O₂₀)(OH)₄ ^. 2H₂O. Different parameters like acid concentration, contact time, amount of gel, composition of gel: OPC admixture, effect of temperature, desorption of metal ions from loaded muscovite and effect on crystal morphology due to loading of metal ions were studied. The results has been expressed in terms of distribution coefficient (K_d).</p> </p>     

Radioiodination of insulin using N-succinimidyl 5-(tributylstannyl)-3-pyridine-carboxylate (SPC) as a bi-functional linker: Synthesis and biodistribution in mice</p> </p>

Summary Insulin receptors are overexpressed on a number of human tumors, leading to significant affinity of insulin to these tumors. It is appealing to receptor-targeted radiotherapy for malignant tumors if insulin is labeled with suitable radionuclide. In this paper, N-succinimidyl 5-(tributylstannyl)-3-pyridinecarboxylate (SPC), a potential bi-functional linker for radioiodination of proteins or peptides, was synthesizedby using 5-bromonicotinic acid as the starting material. Then, with this bi-functional linker, insulin was conjugated with ¹³¹I, and the tissue distribution of the labeled insulin (¹³¹I-SIPC-insulin) in normal mice was investigated. The results showed that insulin ^</span> could be conjugated with¹³¹I using SPC as the linker ^</span> in a labeling yield of40-58%, and with radiochemical purity of more than 98% after purification bySephadex?G-10. Even kept at room temperature for 72 hours, the radiochemical purity of ¹³¹I-SIPC-insulin was still more than 97%, implying that the conjugated insulin was constantly stable in vitro.Meanwhile, in order to evaluate the in vivo stability of the conjugated compounds, insulin was also labeled with ¹³¹I by a direct method using chloramine-T (Ch-T) as the electrophilic agents.Biodistribution of¹³¹I-SIPC-insulinin micesuggested that ¹³¹I could clear rapidly from the blood,mainly excreted by kidney. However, ¹³¹I uptake of mice with¹³¹I-SIPC-insulin in some key organs, especially in thyroid and stomach, were much less (150 or 30 times) than that with the direct labeled insulin (¹³¹I-insulin). Additionally, it was noted that ¹³¹I-SIPC-insulin hasmuch betterinvivo stability than¹³¹I-insulin.</p> </p>     

Mixed-valence state of optically active 1',1'”-bis(2-phenylpropyl)-1,1”-biferrocenium salts</p> </p>

Summary The mixed-valence state of 1',1'”-bis(2-phenylpropyl)-1,1”-biferrocenium polyiodides was studied for (R,R), (S,S), (R,S) isomers and the DL modification. The effect of cation symmetry appeared differently from 1',1'”-bis(2-phenylbutyl)-derivatives, while similar packing effect was observed.</p> </p>     

Inorganic ion-exchangers in radioactive waste management</p> </p>

Summary The uptake of indigenously synthesized amorphous stannic and zirconium phosphate was assessed for, one of the important fission fragment, cesium from aqueous solutions using a radiotracer technique. A virtual increase in sorptive concentration (from 1.0 ^. 10^-8 to 1.0 ^. 10^-2 mol ^. dm^-3) and pH (from 2.4 to 10.2) and temperature (from 303 to 333 K) enhanced the uptake of cesium on stannic phosphate. However, the extremely high degree of uptake of cesium on zirconium phosphate was almost unaffected with the dilution beyond 10^-5 mol ^. dm^-3 and pH (i.e., from 2.4 to 10.2) and temperature (from 303 to 323 K). Irreversible uptake occurring for these solids follow the Freundlich adsorption isotherm and the presence of several complexing agents viz., sulphate, phosphate, glycine and EDTA did not affect appreciably the uptake of cesium on zirconium phosphate but it did affect for stannic phosphate system. Both these solids showed good radiation stability towards a 11.1 GBq Ra-Be neutron source having neutron flux ca. 3.2 ^. 10⁶ n ^. cm^{-2 .} s^-1 and associated with a nominalg-dose of ca. 1.72 Gy/h, at least for the uptake of cesium.</p> </p>     

Strontium isolation from natural samples with Sr resin and subsequent determination of 90Sr</p> </p>

The reliability of an ⁹⁰Sr determination method was tested using an Sr extraction chromatographic resin for strontium isolation. The ⁹⁰Sr-content in samples of vegetables, soil and water (obtained from Environmental Measurement Laboratory, USA) were determined and the results were controlled by classical methods and by using an anion-exchanger and an alcohol solution of nitric acid for the strontium isolation. These methods were previously tested by determining ⁹⁰Sr in IAEA 326 and 327 samples of soil. It is shown that the isolation process with Sr resin is simpler and faster than the classical and mixed solvent anion-exchange methods. The efficiency of isolation on a Sr column depends on the resin quantity and separation conditions; and is the highest with a Sr column, compared to the classical and anion-exchange methods. Experimental data and theoretical models were used to calculate the parameters that enable the estimation of optimum dimensions of the column for isolation. A simple relation is proposed for the calculation of breakthrough volume, which defines the sample and eluent volumes for an optimal strontium isolation.</p> </p>     

Cascade ultrafiltering of 210Pb and 210Po in freshwater using a tangential flow filtering system</p> </p>

Summary A rapid method was developed using ultrafilters with a tangential flow filtering system for molecular size separation of naturally occurring ²¹⁰Pb and ²¹⁰Po in a freshwater sample. Generally, ultrafiltering of a large volume water sample for measuring the nuclides was too time consuming and not practical. The tangential flow filtering system made the filtering time short enough to adapt for in-situ ultrafiltering the large volume sample. In this method, a 20 liter water sample was at first passed through the 0.45mm pore size membrane filter immediately after sample collection to obtain suspended particle matter [>0.45mm particulate fraction (PRT)]. Two ultrafilters (Millipore Pellicon 2^ò) were used sequentially. The nuclides in the filtrate were separated into three fractions: high molecular mass (100 kDa-0.45mm; HMM), low molecular mass (10 k-100 kDa; LMM) and ionic (<10 kDa; INC) fractions. It took 80 minutes to process the sample after collection. The cut-off molecular size of each ultrafilter was confirmed by size exclusion chromatographs (SEC) of the LMN and the HMM fractions. Adsorption of the nuclides and organic compounds in the sample onto the ultrafilters was negligibly small. Good reproducibility of the nuclide concentrations in each fraction was confirmed by repeated experiments. The method was successfully applied to obtaine the molecular size distributions of ²¹⁰Pb and ²¹⁰Po in an oligotrophic lake, Lake Towada located in the northern area of Japan.</p> </p>     

Macro micro separation of selenium and tellurium: Application to NAA</p> </p>

Summary A simple pre-irradiation separation approach has been worked out for the determination of traces of tellurium in high purity selenium followed by neutron activation analysis (NAA) for the end determination of the analyte/s. The difference in volatilities of these elements has been utilized for the separation of the analyte from the matrix. The complete volatility of selenium at ~600 °C was established using neutron activation analysis and selenium radiotracer. Standard addition was used to validate the results. The proposed method of separation of selenium prior to irradiation could make the determination of tellurium possible and also improved the detection limit by several folds.</p> </p>     

Radiation effects on gaseous iodine at very low concentrations</p> </p>

Summary Exploratory experiments have been carried out to investigate the effects of gamma-radiation on iodine aerosols under various chemical conditions. The results indicate that iodide ions (I^-) in aerosol can be readily oxidized to I₂ and HIO, and some iodide ions may be converted to organic iodine when organic additives are present in the KI solution from which the aerosol is generated. The results also suggest that the chemical transformation of irradiated iodine aerosol depends on the chemical environment both carrier gas and iodide solution.</p> </p>     

Transfer of 226Ra, 85Sr and 137Cs from milk to milk products</p> </p>

Summary Transfer of ²²⁶Ra, ⁸⁵Sr and ¹³⁷Cs from cow and sheep milk to various Syrian dairy products has been evaluated. Dairy products include Kashkivan cheese, braided cheese, Haloom cheese, Sircassian cheese, liquid cheese, native cheese, cottage, thick yogurt, butter and milk cream. The results showed that the percentage of ²²⁶Ra, ⁸⁵Sr and ¹³⁷Cs transferred from cow milk to milk cream (P_t=food processing retention factor′processing efficiency′100%) has reached 32%, 16% and 7%, respectively. Butter and liquid cheese were found to have the lowest percentage of transferred 226Ra, ⁸⁵Sr and ¹³⁷Cs. Most of the obtained P_t values of the studied radionuclides in thick yogurt were relatively low in spite of the high processing efficiencies of thick yogurt. Moreover, the transfer, P_t, of the studied radionuclides from cow milk to the prepared cheese was higher than those values determined for sheep milk. This is due to differences in chemical compositions of each type of milk. On the other hand, the treatment of Native cheese, most commonly consumed cheese in Syria, with different concentrations of NaCl solutions showed that ¹³⁷Cs was completely removed from cheese soaking in 5% NaCl solution (soaking time of 48 hours), while 40% of ²²⁶Ra and 80% of ⁸⁵Sr were also decontaminated using 0-2.5% NaCl solutions and soaking time of 48 hours. Based on the obtained results, industrialization processes of the dairy products that resulted the removal of radionuclides have been identified.</p> </p>     

Simultaneous measurement of gamma-rays and neutron fluences</p> using a HPGE detector</o:p></p> </p>

Summary A simultaneous determination of gamma and neutron fluences in a mixed neutron + gamma field can be achieved by gamma-ray spectrometry, optimizing the moderator-converter-detector assembly and measuring both the direct gamma-lines and the neutron induced prompt gammas. For the prompt gamma-lines a combination of high efficiency and low background is the goal, and it can be best achieved if the gamma-energy is in the range above about 1 MeV up to 2.5 MeV. The optimal moderator-converter thickness can be determined experimentally. Most converter elements produce gamma-rays in the low energy range. If chlorine is used as a converter, the 1164.7 keV peak and the 1950-1960 keV peaks seems to be a good choice. A very practical material containing chlorine is PVC. It is an efficient moderator, it is solid, common, and can be handled easily.</p> </p>     

Factors affecting the sorption of Eu(III) on modified silica gel</p> </p>

Summary 8-Hydroxyquinoline in benzene, xylene, chloroform and toluene diluents was used to modify silica gel as a solid phase extractant (SPE) for the sorption of Eu(III) in batch extraction techniques. Influences of solid/liquid ratio, pH, metal ion concentration, particle size and temperature were studied. The optimum initial pH is 4.2, while the maximum sorption capacities for the prepared impregnated resins in benzene, xylene, chloroform and toluene diluents are 18.52, 14.98, 14.79 and 5.94 mg ^. g^-1, respectively. The sorption process is found to be affected by both metal ion concentration and particle size of the impregnated resin. Thermodynamic parameters for the sorption of Eu(III) were determined and the reaction is found to be exothermic and spontaneous with enthalpy-14.23 and-23.71 kJ ^. mol^-1 for benzene and xylene as diluents. Release of the element from the loaded solid particles into 0.01M HNO₃ is@85% and@53% from 8-HQ/benzene/silica gel and 8-HQ/xylene/silica gel.</p> </p>