Strontium recovery

Filippov, E.A., Dzekun, E.G., Nardova, A.K. Mamakin, I.V., Gelis, V.M., Mityutin, V.V. Application of crown-ethers and ferrocyanide-based inorganic materials for cesium and strontium recovery from high-level radioactive wastes. In Proc. Symp. Waste Management, Tucson, AZ, Vol. 2, 1992, pp. 1021-1024. 

Filippov, E. A., Dzekun, E. G., Nardova, A. K., Mamakin, I. V., Gelis, V. M., and Milyutin, V. V. Application of Crown Ethers and Ferrocyanide-Based Inorganic Material for Cesium and Strontium Recovery from High-Level Radioactive Wastes, Proc. Waste Management 92, Tucson, Arizona, U.S.A., Mar. 1-5, 1992, pp. 1021-1025. 

Figure 8 A scheme for strontium recovery from mixtures of sodium and calcium chloride.

Synthetic and natural zeolites have also been intensively investigated. They are inexpensive and widely available sorbents that should be employable for strontium recovery. Some of these sorption materials, such as type A zeolites and natural chabazite are known to be effectively employed for the removal of radioactive strontium from technological solutions [246, 247] so contaminated. 

Clinoptilolite has been demonstrated to be the most appropriate sorbent for strontium recovery from seawater, as well as ftom other natural waters and brines [248-250]. This most common zeolite is characterized by the composition (Na, IO4 CaAl6Si3o072 24 H2O. The main advantages of applying clinoptilolite for recovery of strontium from seawater is attributed to the ease with which it is regeneratable by ammonium salts... 

Figure 13 Concentrations of alkali earth metals at different stages of the cascade process in the course of strontium recovery from seawater (see text).

Selective separation of strontium from calcium at significant SrCl2 concentration levels up to 2 g/L was obtained with KB-4 carboxylic add exchanger employed in a Higgins-type contactor [246]. The pilot unit for strontium recovery from seawater in the closed (and practically waste-free) processing scheme was constructed in the Okhotsk Sea region (Sakhalin power station). The data obtained with the new pilot plant have shown that several components will be recovered simultaneously from seawater. The unit is estimated to produce more than 150 kg of SrCOj, more than 5000 kg of KNOj, and about 2 kg of RbNOj [15]. However, recovery of strontium is still uneconomical. Its cost is expected to become comparable to that of strontium produced from traditional, land-based sources. 

The developed method generally follows the recommendations of the method RP515 from the U.S. D.O.E. A known volume of sample (500 mL) is acidified to 2 M HNO3. Sr tracer in O.IM HCl - ImM Sr(N03)2 is added to the sample to determine strontium recovery (activity between 10 and 20 Bq). Samples are filtered. Disk rinsing with 2 M HNO3 and dionized water eliminates possible interfering radioisotopes. Sr is then eluted with 6 mL of 0.025 M sodium EDTA (pH=l 1). 5 mL of the 6 mL of eluate are transferred in a liquid scintillation vial. These are counted at Sr/ Y equilibrium (about 3 weeks) after scintillation cocktail adding. 

Horwitz, E. R, Dietz, M. L., Fisher, D. E. I., Srex A new process for the extraction and recovery of strontium from acidic nuclear waste streams, Solv. Extr. Ion Exch., 9,1-25, 1991. 

Complexes of alkali metals and alkaline-earth metals with carbohydrates have been reviewed in this Series,134 and the interaction of alkaline-earth metals with maltose has been described.135 Standard procedures for the preparation of adducts of D-glucose and maltose with the hydroxides of barium, calcium, and strontium have been established. The medium most suitable for the preparation of the adduct was found to be 80% methanol. It is of interest that the composition of the adducts, from D-glucose, maltose, sucrose, and a,a-trehalose was the same, namely, 1 1, in all cases. The value of such complex-forming reactions in the recovery of metals from industrial wastes has been recognized. Metal hydroxide-sugar complexes may also play an important biological role in the transport of metal hydroxides across cell membranes. 

Draye, M., Favre-Reguillon, A., Foos, J., Guy, A., Lemaire, M. 1997. Radiochemical stability of dicyclohecano-18-crown-6 ether (DCH18C6) and its use in a recovery process of strontium from acidic nuclear waste stream. Radiochim. Acta 78 105-109. 

Smalley P.C., Raiheim A., Dickson J. A.D. and Emery D. (1988) 87Sr/86Sr in waters from the Lincolnshire Limestone aquifer, England, and the potential of natural strontium isotopes as a tracer for a secondary recovery seawater injection process in oilfields. Applied Geochem. 3, 591-600. 

YSr = chemical yield for the recovery of the strontium carrier (mg Sr recovered/ mg Sr added),... 

Step 13. Turn off the heat lamp, cool planchet to room temperature, and promptly weigh the planchet with strontium nitrate to the nearest 0.1 mg. Record the weight in Data Table 14.1. The weight of strontium nitrate is determined to identify any significant deviation in recovery among samples, relative to the QC sample. The weight can also indicate the extent of self-absorption. 

D. W. Collier,87 in a recent patent, reports that the use of a small amount of barium and/or strontium salts in conjunction with the calcium and/or magnesium salts ordinarily used in the precipitation of the aconitic acid from molasses gives much higher aconitate recoveries than those previously reported. The use of a small amount of either barium or strontium salts causes much greater precipitation than an equivalent amount of calcium ion. Thus the use of a mixture of a calcium salt and a barium salt which contained cations equivalent to the aconitic acid (90% equivalence of calcium ion and 10% equivalence of barium ion) in a trisodium aconitate solution was found to give a residual aconitate solubility (3.1 g./liter) much lower than that (12.6 g./Iiter) obtained when an equivalent amount of calcium ion was used alone. 

Modifications to this process can be made to effect recovery of neptunium, americium, curium, californium, strontium, cesium, technetium, and other nuclides. The efficient production of specific transuranic products requires consideration of the irradiation cycle in the reactor and separation of intermediate products for further irradiation. 

The analyte was concentrated (enrichment factor 200) but high levels of natural strontium in the separated fraction (of about 1 jxg mF ) meant higher detection limits (80 pg 1 ) due to peak tailing of Sr+ atm/z = 90 and the relatively low abundance sensitivity of ICP-SFMS at a medium mass resolution of 6 x 10 . This detection hmit in the separated fraction corresponded to a detection limit of O.TpgT in the original urine sample. The recovery of °Sr, determined by the described analytical method in spiked urine samples, was in the range 82-86 %. Decreasing the detection hmit for °Sr determination is recommended by the apphcation of a multiple ion collector ICP-MS due to improved abundance sensitivity. The analytical methods described can also be applied for the analysis of other body fluids, such as blood or human milk or for the determination of °Sr in bones. 

According to the latest estimates of Skinner [18], elements potentially recoverable from seawater are sodium, potassium, magnesium, calcium, strontium, chlorine, bromine, boron, and phosphorus because of their practically unlimited presence in the ocean. After improving respective technologies, recovery of the following elements is expected to become profitable as well lithium, rubidium, uranium, vanadium, and molybdenum. Additional profit can be gained since desalinated water will probably be obtained as a by-product. This could be important for countries with a very limited number of freshwater sources (e.g., Israel, Saudi Arabia). 

The additional presence of 50-100 mg/L of strontium in the ammonium stripping solution remains one of the major problems in applying clinoptilolite for the recovery of strontium. Selective separation of strontium and calcium before precipitating SrCOj as a pure final product also remains a sizable problem. A possible solution to this problem may be provided by applying cascade schemes [15]. Such treatment of strontium concentrate could include columns with fixed beds of selective and auxiliary sorbents, e.g., [KU-2—Cli] [KU-2—Cli] —> etc., where brack-... 

The number of publications involved with the recovery of rubidium from seawater is very limited. Most of the work in this field is by Russian scientists, who have proposed several schemes for the combined recovery of rubidium, strontium, and potassium with natural zeolites [15, 19, 250-253, 257]. A number of inorganic sorbents with high selectivity toward rubidium were also synthesized for the recovery of rubidium from natural hydromineral sources, including seawater. Ferrocyanides of the transition-metal ions were shown to exhibit the best properties for this purpose [258, 259]. Mordenite (another natural zeolite) has recently been proposed for selective recovery of rubidium from natural hydromineral sources as well [260]. A review of the properties of inorganic sorbents applicable for the recovery of rubidium from hydromineral sources has been published [261]. Studies of rubidium recovery fix>m seawater [15, 19, 250-253] have shown that the final processing of rubidium concentrates, especially the selective separation of Rb -K mixtures remains the major problem. A report was recently published showing that this problem can be successfully solved by countercurrent ion exchange on phenolic resins [262]. 

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