Separation of strontium from calcium by means of anion exchanger and alcoholic solution of nitric acid

A possibility of mutual separation of calcium and strontium on an anion-exchange column has been studied and then used in working out methods of separation of radioactive strontium from natural samples. All examinations, carried out on model systems, showed that calcium could be completely separated from strontium on the column with the anion exchanger Amberlite CG-400 using 0.25M HNO₃ in methanol as eluent. The flow velocity of this eluent in the range between 1 ml/min and 5 ml/min did not influence the efficiency of separation of calcium from strontium. The increase of the concentration of nitric acid in methanol reduced the efficiency of their mutual separation and the increase of exchanger column height neutralized the influence of the increase of acid concentration. Calcium was separated from strontium in the mass concentration ratio (Ca²⁺)/(Sr²⁺) in the range between 11 to 1001. This separation procedure may be used for the isolation of radioactive strontium from real samples instead of using fuming nitric acid.     

Separation and Preconcentration of Strontium from Calcium in Aqueous Samples by Supported Liquid Membrane Containing Crown Ether

Supported liquid membrane containing crown ether (DC18C6) and dinonylnaphthalenesulfonic acid (DNNS) is proposed for separation and preconcentration of strontium in an aqueous environmental sample. The effects of carriers in membrane on permeability and selectivity of Sr²⁺ were characterized. Crown ether has a key role in the selective transport of strontium ion while DNNS facilitates the transport of both Sr²⁺ and Ca²⁺. A strontium ion can be selectively transported to an acidic strip solution against its concentration gradient across the membrane. This SLM can be used as an efficient method for separation and preconcentration of strontium in a neutral aqueous sample.     

Zur Abtrennung des Spaltstrontiums aus Kernbrennstoffen an Ammoniummolybdatophosphat

The separation of fission strontium from solutions of prolonged cooled nuclear fuel has been performed using ammoniummolybdatophosphate (AMP) columns. The sorption mechanism of bivalent ions on AMP has been investigated by column and batch experiments. A pure ion exchange of Sr²⁺ for two H⁺ or NH ₄ ⁺ ions has been established. Conditions for the sorption and elution of fission strontium and other fission products on AMP columns are described.     

Coprecipitation of 15-crown-5 ether complexes of lead and strontium with tungstosilicic acid

Lead as well as strontium form low solubility compounds of composition (ML₂)₂A·nH₂O, (M=Pb²⁺, Sr²⁺), in the presence of 15-crown-5 (L) and tungstosilicic acid (H₄A) in acid media as found by radiometric precipitation titration. “Sandwich” structure of crown-ether complexes of lead and strontium could be expected due to the small size of cavity of 15-crown-5. Coprecipitation of PbL_2/su2+ with crown complexes of strontium cation after adding tungstosilicic acid was studied in 0.01 mol·dm⁻³ HNO₃. A significant influence of H⁺ cation in 1 mol·dm⁻³ HNO₃ on coprecipitation of lead was observed. Formation of HL⁺ complexes by protonisation of 15-crown-5 competes to the formation of ML₂ ²⁺ complexes (approximately twenty percent of 15-crown-5 are used for creation of HL⁺ complexes). Formation of low solubility salts was utilised for separation of lead from strontium in 0.01 mol·dm⁻³ HNO₃. The ratio of constant stability of lead and strontium β‘ with 15-crown-5 in 0.01 mol·dm⁻³ HNO₃ was calculated. The separation factor S(Pb/Sr) depends on the ratio of stability constants β_PbL2/β_SrL2 The precipitation method can be used for separation of metals with high constant stability with crown ethers from solutions containing other metals in the case of gradual addition of crown.     

Removal of Some Radionuclides Using Stannic Silicovanadate as Inorganic Ion Exchanger

Adsorption of cesium (Cs⁺), strontium (Sr²⁺), and europium (Eu³⁺) onto stannic silico vanadate as ion exchange material, and the effects of experimental conditions on adsorption were considered. The material were characterized by X-ray diffractometer system (XRD), scanning electron microscopy (SEM), X-ray fluorescence spectrometry (XRF), infrared (IR), and thermal analysis (TGA and DTA). The selectivity coefficients for different cations determined by mixed solution method were found to be less than unity. The thermodynamic parameters such as ΔG*, ΔS*, and ΔH* have also been calculated for the adsorption of Cs⁺, Sr²⁺, and Eu³⁺ onto stanic silicovanadate, showing that the overall adsorption process is spontaneous and endothermic.     

Improved method for the separation of radioactive strontium from various samples by mixed solvent anion exchange

Procedures for the separation and determination of⁹⁰Sr in liquid samples, with cation and anion exchangers have been described. Strontium, yttrium and other cations bind to the cation exchanger and are eluted from the column by means of nitric acid. Separation of yttrium and strontium from other cations is carried out on columns filled with strong base anion exchangers in nitrate form with alcoholic solutions of nitric acid. This separation method enables the determination of⁹⁰Sr through yttrium on a low-level gas flow α, β-counter, as well as through strontium on a lowlevel liquid scintillation counter by means of Cherenkov counting. Such procedures have been tested by the determination of⁹⁰Sr in water, wine, medium radioactive liquid waste samples, milk and clover samples. For comparison, the determination has also been carried out by the standard method. It has been showed that the developed procedures might produce a high efficiency in strontium separation and a satisfactory accuracy of determination.     

Extraction separation of Cs+, Sr2+ and Ba2+ from a mixture of cations forming stable non-extractable complexes with ethylenediamine-N,N, N′,N′-tetraacetic acid in the water-nitrobenzene system

In the two-hase water-nitrobenzene extraction system, a method for gradual separation of Cs⁺, Sr²⁺ and Ba²⁺ from the mixture of cations forming stable non-extractable complexes with ethylenediamine-N, N, N,N-tetraacetic acid in the presence of the sodium salt of dicarbollylcobaltate anion {[-(3)-1, 2-B₉C₂H₁₁]₂ Co(III)}^– and polyethylene glycol ligand with a mean relative molecular mass of 400 (PEG 400), respectively, was developed. In the first extraction step, Cs⁺ was extracted into the organic phase while the other cations studied (Ca²⁺, Sr²⁺, Ba²⁺, Zn²⁺, Co²⁺, Ce³⁺) remained in the aqueous phase. In the second extraction step, Sr²⁺ and Ba²⁺ were extracted into the nitrobenzene phase. Finally, in the following reextraction step, Sr²⁺ was transferred into the aqueous phase while Ba²⁺ remained in the organic phase.     

Extraction separation of barium from strontium in a two-phase water-nitrobenzene system

A rapid extraction separation of Ba²⁺ from Sr²⁺ with a nitrobenzene solution of sodium dicarbollylcobaltate /NaDCC/ in the presence of polyethylene glycol having mean relative molecular weight 400 /PEG 400/ and tetrasodium salt of trans-cyclohexane-1,2-diamine-N,N,N,N-tetraacetic acid /Na₄L/ was developed. The separation factor _Ba/Sr was approximately 10⁴.     

Indirect ultraviolet detection of alkaline earth metal ions using an imidazolium ionic liquid as an ultraviolet absorption reagent in ion chromatography

A convenient and versatile method was developed for the separation and detection of alkaline earth metal ions by ion chromatography with indirect UV detection. The chromatographic separation of Mg²⁺, Ca²⁺, and Sr²⁺ was performed on a carboxylic acid base cation exchange column using imidazolium ionic liquid/acid as the mobile phase, in which the imidazolium ionic liquid acted as an UV‐absorption reagent. The effects of imidazolium ionic liquids, detection wavelength, acids in the mobile phase, and column temperature on the retention of Mg²⁺, Ca²⁺, and Sr²⁺ were investigated. The main factors influencing the separation and detection were the background UV absorption reagent and the concentration of hydrogen ion in ion chromatography with indirect UV detection. The successful separation and detection of Mg²⁺, Ca²⁺, and Sr²⁺ within 14 min were achieved using the selected chromatographic conditions, and the detection limits (S /N = 3) were 0.06, 0.12, and 0.23 mg/L, respectively. A new separation and detection method of alkaline earth metal ions by ion chromatography with indirect UV detection was developed, and the application range of ionic liquids was expanded.     

Precipitation separation of lead and calcium,strontium, barium from acidic solutions using crown ether and tungstosilicic acid

It was found that lead reacts with 18-crown-6 (L) and tungstosilicic acid (H₄A) in acidic solutions and a compound with low solubility is formed what was confirmed by radiometric titration methods. Coprecipitation of complexion cation of PbL²⁺ with similar complexion cations of calcium, strontium and barium was studied. Formation of low soluble salts was utilized for separation of Pb from Ca, Sr and Ba from 1 mol·dm^–3 HNO₃. The ratio of Pb/Ca, Pb/Sr and Pb/Ba in the precipitation or separation factors S_pb/M undoubted depends on the ratio of the stability constants of lead and metals with 18C6 (_Pb/_M), what can be used for determination of more precise constant stability _M.     

Use of Microspherical Sulfonated Hypercrosslinked Polystyrene in Ion Chromatography

The possibility of applying sulfonated cation exchangers on the basis of hypercrosslinked polystyrene (HCPS) of different ion-exchange capacity for the ion-chromatographic separation of alkali metal and ammonium cations was demonstrated. The effect of the nature and concentration of the eluent, the temperature of the chromatographic column, additions of an organic solvent to the eluent, and the ion-exchange capacity of the sorbent on the retention of cations was examined. An unusual selectivity of the sorbent for lithium and ammonium cations was found; the elution order can change for the Li⁺/Na⁺ and Rb⁺/NH⁺ ₄ pairs depending on the nature of the eluent, the temperature, additions of an organic solvent, and the structural characteristics of the sorbent. When dilute solutions of nitric acid are used as the eluent, the following elution order of cations was obtained: Na⁺ < Li⁺ < K⁺ < NH⁺ ₄ < Rb⁺ < Cs⁺ Mg²⁺ < Sr²⁺ < Ca²⁺ < Ba²⁺. Under the optimum conditions of separation (1 mM solution of sulfuric acid, 20°C) on sulfonated HCPS with an ion-exchange capacity of 0.07 mequiv/g, the separation of ammonium and alkali metal cations was achieved within 17 min.     

Specific interactions of alkenes with different metal ion forms of ion exchangers in gas solid chromatography

Summary The gas chromatographic selectivity of K⁺, Zn²⁺, Ag⁺, Ni²⁺, and Cd²⁺ forms of a cation exchange packing have been determined for a set of 44 C₂ to C₈ alkenes. The retention characteristics of each ion are broken down into electronic (charge-transfer) and steric effects associated with the alkene sub-populations of each carbon number. Almost every pair of alkenes tested can be separated on at least one of these packings. Retention is much stronger on the ion exchangers than on metal-ion containing packings in gas-liquid chromatography, even with shorter columns and higher temperatures.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Sorption of Copper and Strontium Ions and Fulvinate and Citrate Complexes from Aqueous Solutions by Flocculating Microbocenosis

Sorption of copper and strontium ions and citrate and fulvinate complexes by the microorganisms of natural activated sludge is studied. It is shown that the latter contains charged hydrophilic and hydrophobic biocolloids and capable of active sorbing of copper and strontium ions, as well as their organic complexes, from aqueous solutions. It is established that metal ions possess a higher affinity for a given microbocenosis than their organic complexes and the limiting sorption of metal compounds within a concentration range of 0.1–1 mM is equal to (in mmol/g): 0.646 (Cu²⁺), 0.177 (Cu-fulvinate), 0.156 (Cu-citrate), 0.495 (Sr²⁺), 0.364 (Sr-fulvinate), and 0.292 (Sr-citrate). Copper ions and organocomplexes are bound to the activated sludge stronger than corresponding compounds of strontium.     

Extraction and theoretical study on complexation of the strontium cation with antamanide

By using extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Sr²⁺(aq) + 2A^?(aq) + 1(nb) ? 1·Sr²⁺(nb) + 2A^?(nb) occurring in the two-phase water–nitrobenzene system (A^? = picrate, 1 = antamanide; aq = aqueous phase, nb = nitrobenzene phase) was determined as log K _ex (1·Sr²⁺, 2A^?) = ?0.3 ± 0.1. Further, the stability constant of the 1·Sr²⁺ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log β _nb (1·Sr²⁺) = 8.8 ± 0.1. Finally, applying quantum mechanical density functional level of theory calculations, the most probable structure of the cationic complex species 1·Sr²⁺ was derived. In the resulting complex, the “central” cation Sr²⁺ is bound by six bond interactions to the corresponding six oxygen atoms of the parent ligand 1. The interaction energy of the considered 1·Sr²⁺ complex was found to be ?1,114.9 kJ/mol, confirming the formation of this cationic species as well.     

Influence of co-ions in the eluent on the separation factor of lithium isotopes

The influence of co-ions in the eluent on the separation factor () of lithium isotope separation has been studied by ion exchange chromatography. A strongly acid cation exchange resin (Dowex 50W-X8) was used for the separation of lithium isotopes. The co-ions used in eluent were H⁺, K⁺, Ba²⁺, Cu²⁺, Al³⁺ and Cr³⁺ as their chlorides. From the experiments, it was found that⁶Li was enriched in the resin phase and⁷Li in solution phase. At the same distribution coefficient (K_d=30), the separation factor increased linearly with the charge of co-ion (=1.0022 to 1.0039).     

Ionenaustauschchromatographie mit gepackten Capillars?ulen und amperometrischer Detektion

Zusammenfassung Herstellung und Anwendung gepackter Capillarsäulen (innerer Durchmesser: 0,3 mm) zur analytischen Trennung von Kationen durch Komplexelution im Mikromaßstab werden beschrieben. Als Säulenpackung dienen Kugeln eines stark sauren Kationenaustauschers mit einem mittleren Durchmesser von 25 . Die Detektion der getrennten Kationen erfolgt kontinuierlich im Effluent mit Hilfe einer amperometrischen Mikromeßzelle. Die Trennleistung einer 125 mm langen Capillarsäule wird am System Ni²⁺/Co²⁺/Iminodiessigsäure gezeigt. Die dosierten Probemengen liegen in der Größenordnung von 5–12 g je Kation.

---

Summary Preparation and application of packed capillary columns (interior diameter: 0.3 mm) for analytical separations of cations in micro-scale by means of complex elution are described. The capillary columns are filled with spherical grains in the range of 25 .The detection of separated cations in the effluent is performed by means of an amperometric micro-cell.The separation efficiency of a capillary column (length: 125 mm) is shown for the system Ni²⁺/Co²⁺/iminodiacetic acid. The injected quantities of samples are in the range of 5–12 g per cation.

---

---

Herrn Dr. habil. K. Wetzel danken wir für Anregungen und Diskussionen, den Herren W. Rose und K. Rupprecht für praktische Unterstützung bei der vorliegenden Arbeit.     

Synthesis and Crystal Structure of Diaqua(2.2.2-Cryptand)strontium Dichloride Trihydrate

Absract—Diaqua(2.2.2-Cryptand)strontium dichloride trihydrate [Sr(2.2.2-Crypt)(H₂O)₂]²⁺ · 2Cl^– · 3H₂O (I) was prepared and studied by X-ray diffraction. The triclinic structure of I (space group P , a = 9.152 Å, b = 10.140 Å, c = 15.219 Å, = 88.84°, = 88.19°, = 87.62°, Z = 2) was solved by the direct method and refined by full-matrix least-squares calculations in the anisotropic approximation to R = 0.050 for 4188 independent reflections (CAD4 automated diffractometer, CuK radiation). The structure contains the [Sr(2.2.2-Crypt)(H₂O)₂]²⁺ host–guest cation. The Sr²⁺ cation resides in the 2.2.2-cryptand cavity and is coordinated by all eight heteroatoms (6O + 2N) of the cryptand ligand and by two O atoms of water molecules. The Sr²⁺ coordination polyhedron (C.N. 10) is a highly distorted dibase-centered two-cap trigonal prism. The crystal structure of I contains a branched system of ion–ion (intermolecular) hydrogen bonds O(w)–H···Cl^–, which connect the complex cations, the Cl^– anions, and the crystal water molecules to form infinite thick layers parallel to the yz plane.     

Serial separation of cations and anions by ion chromatography using the peak parking technique and sulfosalicylic acid as the eluent

An improvement of the peak parking technique is described for the serial determination of cations (Na⁺, , K⁺, Mg²⁺, and Ca²⁺) and anions (Cl⁻, , and ) using a single pump, a single eluent and a single detector. The present system used commercially-available unmodified cation exchange and anion exchange columns, which were attached to each switching valve. When 1.75 mM 5-sulfosalicylic acid was used as the eluent, serial separation of the above cations and anions was achieved in less than 20 min. The proposed ion chromatographic method was successfully applied to the serial determination of cations and anions in tap water and river water samples. The limits of detection at S/N=3 for an injection of 20 μl were 16–68 ppb (μg/l) for cations and 15–28 ppb for anions.     

Preferential mycobacterial adsorption of radionuclides in filiation

Measurements of Group IIA/IIIB cation adsorption by non-proliferative suspensions of Mycobacterium smegmatis in acidic medium show regular trends in percent adsorption and specific uptake of both ion types in the⁹⁰Sr/⁹⁰Y filiation for carrier concentrations in the range 50–2000 M. In comparative measurements with the⁴⁷Ca/⁴⁷Sc filiation, the corresponding adsorption of Sc³⁺ is consistently higher than that of Y³⁺, and both ions are preferentially adsorbed with respect to the divalent species Sr²⁺ and Ca²⁺. Ion separation efficiency in the calcium/scandium pair is more pronounced at lower concentrations and appears highest in the 100 M carrier region.     

Ion-pair extraction and fluorimetric determination of ultratraces of strontium with cryptand 2.2.2 and eosin

A highly sensitive and selective fluorimetric determination of strontium is proposed, based on solvent extraction of the ion-pair formed between the cationic complex of Sr²⁺ with cryptand 2.2.2 and eosinate as counter ion. A linear working range from 0.7 ng/ml (limit of detection) to 500 ng/ml of strontium and a relative standard deviation of 3.5% at the 100 ng/ml level are obtained. The metal: ligand: counter ion molecular ratio in the extracted mononuclear ion-pair is 1 1 1. The equilibrium constants involved in the extraction process were calculated.