Cesium Distribution Coefficients Research Articles

MODIFIED TITANIUM PHOSPHATES AS CESIUM SELECTIVE ION EXCHANGERS

ABSTRACT Two synthetic methods for the preparation of spherically granulated titanium phosphates (TiP), as cesium selective exchangers, have been carried out. The first method uses the “ion memory” effect for the formation of specific adsorption sites in the matrix of TiP, whereas the second method results in the preparation of granular titanium phosphate - ammonium molybdophosphate (TiP-AMP) composites by a gel technique. The efficiency of the new materials has been studied in complex systems. The cesium distribution coefficients for some of the sorbents prepared are higher than 40,000 mL/g. It was found that, due to high exchange capacity, regenerability and high selectivity for cesium, TiP materials with “ion memory” effect can be used for radiocesium recovery from ground and surface waters, whereas granular composite TiP-AMP exchangers are useful for the treatment of cesium containing acid nuclear wastes with a high content of background electrolytes.

Cesium Absorption from Acidic Solutions Using Ammonium Molybdophosphate on a Polyacrylonitrile Support (AMP-PAN)

Recent effort at the Idaho Chemical Processing Plant (ICPP) have included evaluation of cesium removal technologies as applied to ICPP acidic radioactive waste streams. Ammonium molybdophosphate (AMP) immobilized on a polyacrylonitrile support (AMP-PAN) has been studied as an ion exchange agent for cesium removal from acidic waste solutions. Capacities, distribution coefficients, elutability, and kinetics of cesium extraction have been evaluated. Exchange breakthrough curves using small columns have been determined from 1M HNO3 and simulated waste solutions. The theoretical capacity of AMP is 213 g Cs/Kg AMP. The average experimental capacity in batch contacts with various acidic solutions was 150 g Cs/kg AMP. The measured cesium distribution coefficients from actual waste solutions were 3287 mL/g for dissolved zirconia calcines, and 2679 mL/g for sodium-bearing waste. The cesium in the dissolved alumina calcines was analyzed for; however, the concentration was below analytical detectable limits resulting in inconclusive results. The reaction kinetics are very rapid (2-10 minutes). Cesium absorption appears to be independent of acid concentration over the range tested (0.1 M to 5 M HNO3).

Estimation of Cesium Ion Exchange Distribution Coefficients for Concentrated Electrolytic Solutions When Using Crystalline Silicotitanates

Polzer et al.`s method combined with Bromley`s method for estimating activity coefficients and a Langmuir isotherm for cesium in a simple simulated waste solution containing 5.1 M NaNO{sub 3} and 0.6 M NaOH was used to estimate distribution coefficients for cesium in a complex simulated waste solution characteristic of the radioactive tank wastes at Hanford and other US Department of energy sites. The ion exchange material was a hydrous sodium crystalline silicotitanate, labeled TAM-5, which is being developed by Texas A and M University, Sandia National Laboratories, and UOP Associates. Cesium distribution coefficients collected by Bray et al. on a NCAW simulated waste solution were predicted with deviations of less than 25% for solutions containing 1 M, 3 M, and 5 M Na{sup +} and Na:Cs ratios of 10{sup 3}--10{sup 8}. The deviations were less than 5% for the solutions with 1 M Na{sup +}. Cesium distribution coefficients were also predicted and compared with values measured by Egan et al. for TAM-5 and for a storage tank supernate and a newly generated waste solution. Excellent results were obtained for the newly generated waste simulated solution, which did not contain potassium or rubidium.The predictions for the other simulated waste solution weremore » significantly greater than the measured values, because of the presence of large concentrations of potassium or rubidium. The effect of competitive ion exchange between Cs, Rb, and K was not included in the theory. However, the effect of competitive ion exchange between Cs, Rb, and K was not included in the theory. However, the effect of competitive exchange of Cs, Rb, and K appears to be greater for the Oak Ridge simulated waste solution than for the NCAW waste.« less

Transport of Cesium from Reprocessing Concentrate Solutions through Flat-Sheet-Supported Liquid Membranes: Influence of the Extractant

Abstract The influence of the extractant on cesium transport from nuclear fuel reprocessing concentrate solutions to demineralized water through flat-sheet-supported liquid membranes (FSSLMs) was studied using four crown ethers of different lipophility: dibenzo-21-crown-7 (DB21C7), benzo-21-crown-7(B21C7). t-butylbenzo-21-crown-7 (tBuB21C7), and n-decylbenzo-21-crown-7 (nDecB21C7). The distribution coefficients of cesium show that the four crown ethers have similar extraction capacities which follow the sequence nDecB21C7 > tBuB21C7 > B21C7 > DB21C7. DB21C7 and B21C7 cannot be used in cesium transport experiments due to the low organic solubility of the former and the great tendency of the latter to form a third phase between the organic phase and the aqueous extraction phase. Of the other two crown ethers, nDecB21C7 leads to faster cesium transport than tBuB21C7 due to the stronger lipophilic character of the former; this allows a higher crown-ether concentration in the membrane to be obtained when nDecB21C7 is used.

Use of silicotitanates for removing cesium and strontium from defense waste

A new hydrous crystalline silicotitanate (CST), which the authors call TAM-5, has been synthesized that selectively removes cesium cations from solutions containing up to 5.7 M Na[sup +] and for a pH range of less than 1 to greater than 14. In basic media and at the high concentrations of Na[sup +] the CST also removes strontium cations from the solution. For a solution containing 5.7 M Na[sup +], 0.6 M OH[sup [minus]], 5.1 M NO[sub 3][sup [minus]], 100 mg/l Cs[sup +], and 20 mg/l Sr[sup 2+], the distribution coefficients for cesium and strontium are 1,000 ml/g and greater than 4,000 ml/g, respectively. For a solution of 5.7 M NaNO[sub 3], 100 mg/l Cs[sup +] and 20 mg/l Sr[sup 2+] the distribution coefficient for cesium is greater than 10,000 ml/g and for strontium it is equal to 200 ml/g. Experimental studies have also been conducted using complex waste simulants, which compare the performance of this CST and up to 60 other potential ion exchangers/absorbents. These studies substantiate the high selectivity of the CST for cesium in acidic and basic solutions. This new CST, labeled TAM-5, has considerable potential for removing cesium and strontium from defense wastes.

Influence of soil/solution ratio on adsorption behavior of cesium on soils.

The influence of the ratio between soil weight and solution volume (soil/solution ratio) on a distribution coefficient of cesium for coastal sandy soil, kaoline and silica sand to water has been studied. The distribution coefficients of 137Cs for the soils decreased with the increase of the soil/solution ratios. The concentration of the cations dissolved from the soils into the solution varied with the soil/solution ratio. However, when the concentration of coexistent cations kept to be 10–2 mol/l, the distribution coefficient was kept constant at different soil/solution ratios. These results show that the soil/solution ratio does not directly affect on the adsorption of 137Cs on the soils, but the variation in the concentration of dissolved cations with the soil/solution ratio results in the change in the distribution coefficient.

A Review of Information on Ferrocyanide Solids for Removal of Cesium from Solutions

Abstract Ferrocyanide solids have important applications to the removal of radioactive cesium from nuclear waste solutions. These materials are prepared by mixing soluble ferrocyanides and salts of divalent transition metals or other divalent cations. The simple precipitations most commonly give very fine particles or slimes of variable compositions. Special preparation procedures have been developed to control the compositions or to prepare granular solids suitable for column operation. The removal of cesium from solutions has been measured for many different ferrocyanide solids. Some of these solids show an exchange of K+, Na+, or NH4 + for cesium, but many show sorptions of cesium without a true ion exchange. The performance for cesium removal is described by measurements of the distribution coefficients for cesium with large excesses of ferrocyanides, the capacity for cesium with excess cesium in solution, and the rates of cesium removal. The chemical and physical stability, the solubility, and the el...

Features of the exchange of cesium on Co3[Co(CN)6]2·12H2O

The concentration dependence of the kinetics and equilibrium characteristics for the exchange of cesium ions on cobalt hexacyanocobaltate(III) has been studied. It is found that the rate of cesium sorption increases with decreasing cesium concentration in solution. The exchange reaction proceeds via two stages, the first stage is rather fast followed by a much slower one. The equilibrium characteristics of the distribution coefficients for cesium are interpreted in terms of the Langmuir-Huckel isotherm. The heat of sorption and activation energy are determined from the temperature dependence of the exchange reaction.

Additives for the separation of cesium from a strongly nitric acid medium by insoluble ferrocyanide sorbents

In the presence of trace amounts of hydrazinium or amidosulfate ion, sufficiently high values were observed for the distribution coefficients of cesium on several insoluble ferrocyanide sorbents in a concentrated solution of nitric acid, in contrast to considerably lower values in their absence. The results indicate an inhibitory action of the above agents on the oxidation of ferrocyanide to ferricyanide with nitric acid.

The determination of the cesium distribution coefficient of the interim storage soil from Abadia de Goiás, Go, Brazil

In September, 1987, an unauthorized removal of a cesium-therapy unit and its dismantling caused an accident, where several places in the city of Goiânia, capital of Goiás, Brazil, were contaminated. The radioactive waste generated from the decontamination process, was moved to the town of Abadia de Goiás (near Goiânia), where an interim storage was constructed. Soil samples collected from 57th Street (goiânia) and from the interim storage permitted the determination, through static method, of the cesium distribution coefficient for different cesium solution concentrations. Those results allow for some migration/retention evaluations in disposal site selection. Some soil parameters (water content, density, granulometric analysis, etc.) as well as clay mineral constituents were also determined.

Distribution coefficient of cesium and cation exchange capacity of minerals and rocks.

The sorption behavior of cesium on a variety of minerals and rocks has been investigated by batch equilibration using 137Cs. The distribution coefficient (Kd) of cesium increased with decreasing concentration of cesium and approached a constant value in dilute regions. The distribution coefficients determined at a trace level (Kdt,tr) differed more than four orders of magnitude strongly depending on the kinds of samples, for example, about 30 on quartz and 105 on tuffs. The values of Kd,tr are related to the cation exchange capacity (CEC; meq/g) determined from the saturated sorption of cesium for individual samples as : log Kd, tr =log CEC + constant. Most Kd, tr values were found to approximately follow this linear relationship.

SEPARATION OF CESIUM FROM NUCLEAR WASTE SOLUTIONS WITH HEXACYANOFERRATE(II)S AND AMMONIUM PHOSPHOMOLYBDATE

Abstract ABSTRACT The separation of 134, 137 Cs from nuclear power plant low-level waste solutions by ion exchange with potassium cobalt hexacyano-ferrate(II), potassium copper cobalt hexacyanoferrate(II) and ammonium phosphomolybdate was studied. The pH of the waste solutions was 6-13 and the concentrations of sodium and potassium ions were 8 - 2700 and 0.5 - 240 mmol/1, respectively. The distribution coefficient of cesium was determined as a function of pH, sodium and potassium ion concentrations and of the ratio of solution volume to exchanger weight (batch factor). The ion exchange rate of cesium was determined for three exchanger grain sizes and at temperatures of 20, 40 and 60° C. A potassium copper cobalt hexacyanoferrate(II) column was tested for cesium separation from a highly alkaline (pH 13) waste solution containing high concentrations of sodium (2.7 M) and potassium (0.24 M) ions; the 1% breakthrough capacity was very high, 12800 bed volumes.

Cesium deposition on the surface of the sodium coolant circulation loop

The authors measurements of the cesium activity in the circuit of the BOR-60 reactor have shown that the specific activity of /sup 137/Cs in the coolant decreases substantially when the reactor is shut down and increases when the reactor is started up. On the basis of these results, knowing the total surface of the first loop and the volume of the coolant and taking the temperature dependence into account, we determined the effective cesium distribution coefficient for the entire reactor. At 220/sup 0/C this coefficient was 2.2 cm, i.e., virtually coincided with that obtained for the piping. In the shut-down BOR-60 reactor, therefore, approx. 30% of the total amount of cesium in the primary loop (excluding the cold trap) may be located on the surfaces. When the temperature is raised part of the cesium moves from the deposits into the coolant.

Effect of sodium and potassium ions on cesium absorption from nuclear power plant waste solutions on synthetic zeolites

The separation of cesium from low-active waste solutions from a nuclear power plant by ion exchange using synthetic zeolites Zeolon 900 and Linde AW-500 was studied. The pH of the waste solutions was 6–13 and the concentrations of sodium and potassium ions were 8–2700 and 0.5–240 mmol/L, respectively. The distribution coefficient of cesium was determined as a function of pH and sodium and potassium ion concentration. Column breakthrough curves were obtained and an empirical equation was derived to calculate the column performance at different sodium and potassium ion concentrations.

Distribution coefficients for strontium and cesium in overburden at a storage area for low-level radioactive waste : Johnston, H M; Gillham, R W; Cherry, J A Can Geotech JV22, N1, Feb 1985, P6–16

Distribution coefficients for strontium and cesium in overburden at a storage area for low-level radioactive waste : Johnston, H M; Gillham, R W; Cherry, J A Can Geotech JV22, N1, Feb 1985, P6–16

Distribution coefficients for strontium and cesium in overburden at a storage area for low-level radioactive waste

Distribution coefficients for strontium and cesium, as one component of a hydrogeological site investigation, were determined by the batch method on 12 samples of glacial till and 7 samples of sand from the radioactive waste operations site 2 of the Bruce Nuclear Power Development. The tests were performed using two types of equilibrating solutions traced with radioisotopes; one was a solution with cation concentrations equal to the concentrations obtained in 1:1 solid–solution extracts and the other was natural groundwater obtained from piezometers at or near the depths from which the soil samples were obtained. The measured Kd values were relatively uniform within an individual hydrogeological unit, and differences between units were related to the chemical properties of both the solid and solution phases. The Kd values for both Sr and Cs obtained in the tests performed using the synthetic solutions differed from those obtained in tests using natural groundwater. The differences appeared to be related to the major chemistry of the test solutions and indicated that, to obtain Kd values that were most representative of the in situ conditions, natural groundwater should be used in the batch procedure.The measured Kd values, when used in the linear retardation equation, indicated that in the till materials, 90Sr would migrate at a rate no greater than 0.2 cm∙year−1 and 137Cs would migrate at a rate no greater than 0.001 cm∙year−1. Based on the relatively high Kd value for Cs in the sand (300 mL∙g−1), 137Cs migration through the sand unit would be of little environmental concern. On the other hand, the relatively low Kd for Sr (2 mL∙g−1) indicates that attention should be paid to the pathway role of the sand layer in any assessment of the isolation capability of the site.

Sorption and Diffusion of Radionuclides in Rock Matrix and Natural Fracture Surfaces Studied by Autoradiography

AbstractA method based on autoradiography was developed to determine the sorption and diffusion of cesium, strontium, cobalt, nickel, iodine and americium into rock matrix. Samples chosen for this study were filled and unfilled natural fracture surfaces and drill cores having a central drilled hole (”). Rock types were mica gneiss, tonalite and rapakivi granite, which were selected to represent the common rocks and minerals in Finnish bedrock. Distribution coefficients (Ka-values) of cesium and strontium determined for fissure surfaces and drill core cups were of the same order of magnitude. After three months contact time the greatest penetration depth for cesium was 2.5 mm, for a natural fissure surface sample of rapakivi granite. For strontium the penetration depths of 11 mm in three months and 35 mm in twelve months were found for filled natural fissure surface samples of rapakivi granite. The range of Da-values was 1.5 × 10−15 - 3.2 × 10−14 m2/s and 1.4 × 10−14 - 2.1 × 10−13 m2/s for cesium and strontium, resp. For cobalt the Da-values of 5 × 1016 m2/s in tonalite was obtained. In six months the penetration depths of nickel, iodine and americium were too low (< 0.5 mm) to allow calculation of Da.

各種ゼオライトへのセシウム及びストロンチウムの交換吸着に及ぼすほう酸及びアミン類の影響

The ion-exchange properties of cesium and strontium into zeolites from boric acid and amine salt solutions have been studied by the use of zeolite A, mordenite (Zeolon, SM), natural mordenite (NM) and clinoptilolite (CP).The distribution of cesium into mordenite and clinoptilolite from the concentrated boric acid solution (-0.2M) was considerably larger than that into zeolite A. The distribution coefficient of cesium (KCs) into mordenite attained about 103 from acidic solution of pH 1-3. As for strontium, the KSr values into zeolites were in the order of A>SM>>NM.Cesium ions were also preferentially distributed into mordenite from the concentrated amine salt solutions (-1M), and the KCs values exceeded about 7×103 even in 1M solution of amine. The effects of diverse ions on the KCs values into zeolites were in the order of NH4+>Na+>>amines.The KSr values of zeolite A attained about 4×103 in the presence of 1M solution of amine, while those of mordenite were less than 1.7×10102. The distribution of strontium into zeolite greatly depended on pH, and the KSr values decreased with increasing acidity. Therefore, the pH control of the feed solution is considered to be very important.

Significant Results in Low-level Waste Treattvents at ORNL

Operating experience with the 500,000 gal/day waste treatment plant at Oak Ridge National Laboratory has demonstrated that plant efficiency exceeds the design specifications of 50% removal of gross radionuclides. An average of 85-- 90% of the Sr/sup 90/ and Cs/sup 137/ are removed. However, the full potential of the treatment plant can be realized only by modifying the process or by adding to the facility. A number of laboratory experiments were performed to investigate the effect of priraary coagulants, of coagulant aids, and the use of natural minerals, on the removal oi strontium and cesium. By optimizing the comrbination of lime, soda ash, and clay, removal of strontium and cesiunr was increased to 96 and 92%, respectively. Both supplemental phosphate addition to lime-soda softening and aluminum phosphate coagulation removed 98% of the strontium. Coagulant acids reduced the tarbidity in treated waste and resulted in improved efficiency. Vermiculite (grade BO-4), one of the most promising of the minerals investigated, exhibited distribution coefficients for strontium and cesium in excess of 5000 for a solution typical of the effluent from the waste treatment plant. Process changes and possible addition to the plant were evaluated by direct application to the operating plant or bymore » pilotscale tests. (auth)« less

カーナル石中のルビジゥム,セシゥムについて

The fact that the enrichment of rubidium and cesium in carnallite has been pointed out by many workers.The behaviour of trace amount of rubidium and cesium was studied during the crystallisation of halite, sylvite, bischoffite and carnallite, by isothermal evaporation of each of the saturatued solution by use of137Cs and86Rb as tracer.Logarithmic distribution coefficients of rubidium and cesium between the crystal and the solution have been determined as follows : Logarithmic distribution coefficient of rubidium in halite was 0.14, in sylvite was 0.4, in bischoffite was 0.3, and in carnallite was 2.4, and that of cesium in halite was 0.02, in sylvite was 0.03, in bischoffite was 0.3 and in carnallite was 1.3.Those results suggest that rubidium and cesium will be selectively concentrated in carnallite among the oceanic salts.The actual samples of carnallite originated from the oceanic salt deposit in Stassfurt were analysed for chemical composition and X-ray diffraction pattern.The results indicated that one of the samples was the mixture of carnallite, halite and kainite, and the other was perfect carnallite ; cesium contained 1 ppm. in the former and 2 ppm. in the latter, but the Rb/Cs ratio of the former was 90 and that of the latter was 85.The similarity of the ratios and results of the above described experiment suggest that the rubidium and the cesium in the former impure carnallite sample are concentrated only in the carnallite.