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>     

Liquid-liquid extraction of 233Pa(V) with Aliquat 336</p> </p>

Summary The extraction of protactinium with Aliquat 336 (methyl-tri-caprylyl ammonium chloride) in toluene, cyclohexane and chloroform from HCl, HNO₃, H₂SO₄, HClO₄, HF and mixed HCl-HF media was investigated by radioactive tracer technique. Distribution ratios of protactinium between the aqueous solution and the organic phase were determined as a function of shaking time, concentrations of acid in aqueous solution phase, extractant concentration and type of diluents in the organic phase. Aliquat 336 can almost quantitatively extract protactinium from strong HCl solution. At the same time, small amounts of HF in HCl solutions have a strong effect on Pa distribution.</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>     

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>     

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>     

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>     

Removal of strontium ions by a crosslinked copolymer containing methacrylic acid functional groups</p> </p>

Summary A tail-made polymer matrix is proposed to remove strontium ions from aqueous solutions. The removal behavior of strontium ions on a crosslinked copolymer containing methacrylic acid as functional groups was investigated as a function of sorptive concentration, time, temperature and pH. It was observed that an increase of these parameters enhanced the removal of Sr(II) ions from aqueous solution. It is found that a maximum adsorption of Sr(II) ions can be obtained on the crosslinked copolymer after 30 minutes and at pH 8. The increase of Sr(II) ion concentration in the solution resulted in an increase in the amount of Sr(II) ions adsorbed on the crosslinked copolymer containing methacrylic acid as functional groups. However, after a maximum of Sr(II) concentration in the solution, the percentage of adsorbed Sr(II) ions decreased. The adsorption data are well represented by the Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. The adsorption capacity of the copolymer and the free energy change were calculated by using the D-R isotherm. For the adsorption of Sr(II) ions on the crosslinked copolymer the thermodynamic parameters (DH°,DS° andDG°) were calculated.</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>     

Sorption of Co(II) ong-alumina in the presence and absence of fulvic acid</p> </p>

Summary The removal of heavy metal ion Co(II) from aqueous solution was studied usingg-Al₂O₃ by batch technique. The experiments were performed at T=20±2 °C, in 0.01M NaNO₃ solutions and under aerobic conditions. The effect of pH, ionic strength, fulvic acid (FA) and alumina amount on the sorption of Co(II) on alumina were also investigated. The pH affected the sorption of Co(II) significantly as compared with the effect of FA and ionic strength. The results indicated that strong chemical bonds are formed between Co(II) and functional groups of the bare or FA coated alumina, and a precipitation of Co(II) takes place on the alumina surface, induced by a transition from the adsorption to surface. The addition sequences of Co/FA on Co(II) sorption were also studied: the sorption of Co(II) in the ternary system was found independent of addition sequences.</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>     

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>     

Mössbauer study of Fe/S and Fe/O films produced by laser ablation of pyrite and hematite</p> </p>

Summary Pyrite FeS₂ was laser-deposited onto Al substrates at various temperatures, and the M?ssbauer spectra of the films were measured. The yields and the M?ssbauer parameters of FeS₂ and FeS changed depending on the formation temperature, because of the sulfur deficiency in the lattice structures. In addition, hematite Fe₂O₃ was employed as a laser-ablation target, and FeO and Fe₂O₃ were deposited on SiO₂/Si substrates. It was shown that laser-deposition of compounds can produce films that have different chemical species than the laser-evaporated materials.</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>     

Removal of radium from sand filters by inorganic acids</p> </p>

Summary Sand filters are used in water treatment stations to remove particulate matter from underground water, where iron and manganese are collected forming thin oxide films. These oxides of iron and manganese adsorb radium from underground water. Radium concentration increases in time on the filters, and consequently the level of radioactivity increases in the station. The removal of adsorbed radium on sand using inorganic acids was studied. Good efficiency of radium removal was obtained by controlling different parameters like temperature, time, pH, addition of competitive cations and anions. It was found that hydrochloric acid is the best for radium removal from sand filters. Maximum removal obtained was about 60% at 5M BaCl₂ and 2M HCl at 50 °C for 180-minute contact time. Kinetic parameters of the removal process were studied and compared with literature data.</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>     

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>     

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>     

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>     

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>