Studies on the separation of 90Y from 90Sr by solvent extraction and supported liquid membrane using TODGA: role of organic diluent

Solvent extraction and supported liquid membrane transport studies on Y(III) and Sr(II) were carried out using both nitric as well as hydrochloric acid feed conditions using N,N,N′,N′-tetra-octyldiglycolamide (TODGA) in several organic diluents. The solvent extraction studies indicated extremely large separation factor (SF) values with chloroform, carbon tetrachloride, 1-decanol and hexone when 6 M HNO₃ was used as the feed. On the other hand, the SF values were 1–2 orders of magnitude lower when the nitric acid concentration was 3 M HNO₃. Significantly large SF values were also obtained from 6 M HCl when xylene, carbon tetrachloride, n-dodecane and hexone were used as the diluent. Though mass transfer was not very promising in the supported liquid membrane studies with most of the diluent systems, quantitative Y(III) transport was observed with 0.1 M TODGA in xylene with negligible Sr(II) transport suggesting possibility of obtaining carrier free ⁹⁰Y. The purity of the radiotracer was checked by half-life method.     

Retention profile and selective separation of 90Y from 89Sr using zirconium-vanadate gel packed column

A low cost and selective method has been developed for the separation of trace concentrations of ⁹⁰Y³⁺ from its parent ⁸⁹Sr²⁺. The proposed procedure is based upon complete retention of ⁹⁰Y³⁺ onto zirconium-vanadate (Zr-V) gel ion exchanger packed column from aqueous solutions containing HCl (1.0 × 10^?5mol dm^?3). Under these conditions, ⁸⁹Sr²⁺ species were not retained onto Zr-V sorbent. The retained ⁹⁰Y³⁺ species were then recovered with HCl. The performance of Zr-V sorbent packed column was determined via the height equivalent to the theoretical plates (HETP) and the number of plates (N). Validation of the developed method was checked by calculating the radionuclidic purity in terms of purification factor (P _f = A/A₀) and radiochemical purity of the eluted ⁹⁰Y from the column. Zr-V sorbent packed column offers unique advantages of retention and quantitative separation of ⁹⁰Y from retention over conventional solid sorbents in rapid and effective separation of trace concentration of ⁹⁰Y³⁺ from ⁸⁹Sr²⁺ in their aqueous equilibrium media.     

Recovery and purification of Sr(II) in perchloric acid medium

Perchloric acid was found to be a suitable medium for the quantitative leaching of Sr(II) from homogeneous and calcined (Th,Sr)O₂ particularly with respect to the contamination from Th(IV). ⁹⁰Sr is a cause of major concern to the environment due to its long half life (28.6 years), significant abundance in large inventory of spent nuclear fuels (~350 thousand tons) awaiting geological disposal and its chemical similarity to Ca(II), an essential element for the living beings. Application of ⁹⁰Sr as a parent radionuclide for ⁹⁰Y (used in therapy radiopharmaceuticals) is possible provided it can be made available at desired high purity. In this context, the distribution coefficients of Sr(II), Th(IV), Zr(IV), Y(III), ¹⁵²Eu(III) and ¹³⁷Cs(I) were determined using Sr selective crown ether 4,4′(5′)-di-tert-butyl-dicyclohexano-18-crown-6 by solid–liquid extraction in perchloric acid medium. Feasibility of employing extraction chromatography using Sr selective resin for the recovery and purification of Sr(II) from leached perchloric acid medium was explored. Perchloric acid medium is better than nitric acid medium for the uptake of Sr by Sr selective chromatographic resin under varying loading conditions of Sr(II). Similarly pH 2 solution appears better eluent of Sr(II) than distilled water. Present work offers a novel approach for setting up a ⁹⁰Sr–⁹⁰Y generator.     

Diethylenetriamine-functionalized chitosan magnetic nano-based particles for the sorption of rare earth metal ions [Nd(III), Dy(III) and Yb(III)]

The recovery of three rare earth (RE) metals ions [Yb(III), Dy(III) and Nd(III), belonging to heavy, mild and light REs, respectively] was investigated using hybrid chitosan-magnetic nano-based particles functionalized by diethylenetriamine (DETA). The effect of pH on sorption performance was analyzed: the optimum initial pH value was found close to 5 (equilibrium pH value close to 6.5). The nanometric size of sorbent particles (30–50 nm) minimized the contribution of resistance to intraparticle diffusion on the control of uptake kinetics, which is efficiently modeled using the pseudo-second order rate equation: under selected experimental conditions the contact time required for reaching equilibrium was less than 1 h. Sorption isotherms were efficiently modeled using the Langmuir equation: maximum sorption capacities reached about 50 mg metal g^?1, regardless of the RE. The temperature had a very limited effect on sorption capacity (in the range 300–320 K). The thermodynamic parameters were determined: the sorption was endothermic (positive values of ΔH°), spontaneous (negative values of ΔG°) and contributed to increasing the disorder of the system (positive values of ΔS°). The three REs have similar sorption properties on DETA-functionalized chitosan magnetic nano-based particles: the selective separation of these elements seems to be difficult. The sorbed metal ions can be removed from loaded sorbents using thiourea, and the sorbent can be recycled for at least five sorption/desorption cycles with a limited loss in sorption performance (by less than 6 %). The saturation magnetization was close to 20 emu g^?1; this means that nano-based superparamagnetic particles can be readily recovered by an external magnetic field, making the processing of these materials easy.     

Sorption of thallium(III) ions from aqueous solutions using titanium dioxide nanoparticles

Titanium dioxide nanoparticles (NPs) were employed for the sorption of Tl(III) ions from aqueous solution. The process was studied in detail by varying the sorption time, pH, Tl(III) concentration, temperature, and amount of sorbent. The sorption was found to be fast and to reach equilibrium within 2 min, to be less efficient at low pH values, and to increase with pH and temperature. The sorption fits the Langmuir equation and follows a pseudo second order model. The mean energy of the sorption is approximately 15 kJ mol^?1 as calculated from the Dubinin–Radushkevich isotherm. The thermodynamic parameters for the sorption were also determined, and the ΔH ⁰ and ΔG ⁰ values indicate endothermic behavior.     

Separation of 90Y from 90Sr using sequential multiple column extraction chromatography

The distribution coefficient measurements on Y(III) and Sr(II) were performed using ditertiarybutyl dicyclohexano 18-crown-6 (Sr-selective resin) and N,N,N′,N′-tetraoctyldiglycolamide (Y-selective resin) in HNO₃, HCl and HClO₄ media. Separation factors (⁹⁰Y/⁹⁰Sr) based on distribution coefficient data suggested that perchloric acid is distinctly better medium as compared to nitric acid/hydrochloric acid. The mechanism of extraction changes with the nature and concentration of acid and is responsible for the high selectivity in perchloric acid medium. Sequential column studies were carried out on tracers (radioactive/stable) employing Sr-selective/Y-selective extraction chromatographic resins as stationary phases. The final elution of ⁹⁰Y was done in 0.01 M EDTA at pH 4.0 which can be used for clinical applications after radiochemical processing.     

Atmospheric depositional fluxes of cosmogenic <Superscript>32</Superscript>P, <Superscript>33</Superscript>P and <Superscript>7</Superscript>Be in the Sevastopol region

⁹⁰Y was separated from ⁹⁰Sr using an extraction chromatographic resin consisting of 4, 4′(5′)-bis-t-butylcyclohexano-18-crown-6 (DtBuCH₁₈C₆), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide (C₂mimNTf₂), and a polymer (Amberlite XAD-7). Ionic liquid was introduced into the column to improve the separation efficiency. The column showed an excellent performance for the separation of Y from Sr. After the separation, the ratio of ⁹⁰Sr/⁹⁰Y was <2.0 × 10^?5; the column was recycled for >18 times. This study provides preliminary results on columns to produce ⁹⁰Y with a high purity in radiopharmaceuticals.     

Rapid determination of radiostrontium in seawater samples

A new method for the determination of radiostrontium in seawater samples has been developed at the Savannah River National Laboratory (SRNL) that allows rapid pre-concentration and separation of strontium and yttrium isotopes in seawater samples for measurement. The new SRNL method employs a novel and effective pre-concentration step that utilizes a blend of calcium phosphate with iron hydroxide to collect both strontium and yttrium rapidly from the seawater matrix with enhanced chemical yields. The pre-concentration steps, in combination with rapid Sr Resin and DGA Resin cartridge separation options using vacuum box technology, allow seawater samples up to 10 L to be analyzed. The total ⁸⁹Sr + ⁹⁰Sr activity may be determined by gas flow proportional counting and recounted after ingrowth of ⁹⁰Y to differentiate ⁸⁹Sr from ⁹⁰Sr. Gas flow proportional counting provides a lower method detection limit than liquid scintillation or Cerenkov counting and allows simultaneous counting of samples. Simultaneous counting allows for longer count times and lower method detection limits without handling very large aliquots of seawater. Seawater samples up to 6 L may be analyzed using Sr Resin for ⁸⁹Sr and ⁹⁰Sr with a minimum detectable activity (MDA) of 1–10 mBq/L, depending on count times. Seawater samples up to 10 L may be analyzed for ⁹⁰Sr using a DGA Resin method via collection and purification of ⁹⁰Y only. If ⁸⁹Sr and other fission products are present, then ⁹¹Y (beta energy 1.55 MeV, 58.5 day half-life) is also likely to be present. ⁹¹Y interferes with attempts to collect ⁹⁰Y directly from the seawater sample without initial purification of Sr isotopes first and ⁹⁰Y ingrowth. The DGA Resin option can be used to determine ⁹⁰Sr, and if ⁹¹Y is also present, an ingrowth option with using DGA Resin again to collect ⁹⁰Y can be performed. An MDA for ⁹⁰Sr of <1 mBq/L for an 8 h count may be obtained using 10 L seawater sample aliquots.     

Study of the gadolinium sorption on the C100 ion-exchange resin for the development of the antineutrino detector targets

Adsorption of the gadolinium from H₂O and HCl solutions on the ion-exchange resin C100 is investigated. The experiments were carried out by varying the acidity of the liquid phase, the amount of sorbent, and the temperature. The maximal sorption of the ions Gd³⁺ is observed from the solution 0–0.2 M HCl under optimal conditions, the sorption reaches more than 99.5%. Sorption of Gd³⁺ on C100 from H₂O solution occurs most intensively during the first 3 min then for 30 min the system smoothly comes to equilibrium. The maximal sorption capacity of the resin C100 amounted to 1.2 ± 0.1 mmol g^?1. The thermodynamic parameters of sorption: ΔG = ? 24.20 kJ mol^?1, ΔS = ? 90.27 J mol^?1 K^?1, ?H = ? 50.93 kJ mol^?1 were evaluated. It is shown that the sorption of gadolinium on the ion-exchange resin C100 is described by models of kinetically pseudo-first and pseudo-second order. It is established that the Gd³⁺ sorption on the C100 resin is reversible second order chemical reaction.     

Comparative study on lanthanum(III) sorption onto Lewatit TP 207 and Lewatit TP 260

Batch experiments are carried out for the sorption of La(III) onto commercial macroporous resins containing iminodiacetic (Lewatit TP 207) and aminomethylphosphonic acid groups (Lewatit TP 260). The operating variables studied are initial La(III) concentration, pH, temperature and contact time. Since the extraction kinetics were fast, with a mixture of 0.1 g of resin and 5 mL of lanthanum ions 0.5 × 10^?3 mol L^?1 solution, extraction equilibrium was reached within 30 min of mixing. The optimum pH values level for quantitative sorption were between 1.5 and 4.6 with Lewatit 207 and about 5.2 with Lewatit TP 260. The sorption capacities of Lewatit TP 207 and Lewatit TP 260 resins are 114.7 and 106.7 mg g^?1, respectively. Adsorption equilibrium data were calculated for Langmuir and Freundlich isotherms. It was found that the sorption of La(III) on Lewatit TP 207 was better suited to the Langmuir adsorption model while Freundlich adsorption model fitted better sorption on Lewatit TP 260. Thermodynamics data leads to endothermic and spontaneous process. ΔG° decreases with increasing temperature indicating that sorption process of La(III) on both Lewatit TP 207 and Lewatit TP 260 was more favored at high temperature.     

Separation of carrier-free 90Y from 90Sr using flat sheet supported liquid membranes containing multiple diglycolamide-functionalized calix[4]arenes

Abstract

Five diglycolamide-appended calix[4]arene (C4DGA) ligands, viz. C4DGA with no substituent (L-I), n-propyl (L-II), 3-pentyl (L-III), n-octyl (L-IV) and both side (L-V) substituents were evaluated for the separation of carrier free ⁹⁰Y from a ⁹⁰Y–⁹⁰Sr mixture using the flat sheet supported liquid membrane technique. Based on the results of earlier batch studies, the transport properties of the C4DGA ligands towards Y(III) and Sr(II) were monitored at two different feed acidities. The transport rates were significantly lower for 6 M HNO₃ as compared to 3 M HNO₃ as the feed. After 6 h, the observed trend of Y(III) transport with the C4DGA ligands using a feed of 3 M HNO₃ was: L-I ~ L-III > L-V > L-IV > L-II which changed to L-III > L-I > L-IV > L-V > L-II for 6 M HNO₃ as the feed. With 3 M HNO₃ as feed, >97% Y(III) transport was obtained with L-I and L-III in 6 h. Comparative Sr(II) transport was negligible resulting in high decontamination factors. In a one-step separation process, using L-I as the carrier ligand, pure ⁹⁰Y was obtained as the respective complex with either EDTA or DOTA. The highlights of this liquid membrane-based separation method comprise: its easiness, one-step separation, low ligand inventory, relatively pure product and continuous method.     

Adsorption properties of charcoal impregnated with stannic chloride

Adsorption behaviour of the individual tracer ions:¹³⁴Cs(I),^85,89Sr(II),^131,133Ba (II),⁹⁰Y(III),¹⁴¹Ce(III),^152,154Eu(III),⁹⁵Zr(IV),^175,181Hf(IV),⁹⁵Nb(V),⁶⁰Co(II),¹¹⁵Cd(II),^99mTc(VII), and¹³¹I(-I) on charcoal impregnated with stannic chloride from Hcl solutions, was investigated. Batch equilibrium distribution coefficients of the respective ions indicated strong anion exchange properties towards impregnated charcoal. The column breakthrough sorption capacity was of the order of 0.62–0.66 meq·g^–1 of dry adsorbent. Small chromatographic columns of impregnated charcoal could achieve rapid and quantitative separation procedures in HCl medium. Strongly adsorbed anions such as TcO ₄ ^– and I^– ions could be eluted with NH₄SCN and NH₄NO₂ eluents, respectively.     

A new method for the carrier-free production of 90y from 90sr-90y mixture and 89sr from neutron-irradiated y2o3

The extraction of strontium(II) and yttrium(III) ions from aqueous solutions at various pH values into methyl isobutyl ketone containing I-phenyl-3-methyl-4-caprylpyrazolone-5 is described. Quantitative extraction of Sr and Y at pH 8.6–10 and pH 2.8–5.4 respectively is utilized for the carrier-free production of ⁹⁰Y from ⁹⁰Sr–⁹⁰Y mixtures and ⁸⁹Sr from neutron-irradiated yttrium oxide. A clean separation of these elements from each other and more than 95% calculated activities were recovered     

An electrochemical pathway to prepare circular planar 90Sr/90Y sources for the calibration of surface contamination monitors

In this communication, we describe a novel method to prepare circular planar ⁹⁰Sr/⁹⁰Y sources (? = 16 mm) exploiting the intrinsic properties of the anodized titanium to electro-deposit predicted quantity of ⁹⁰Sr activity from an aqueous solution. The influences of various experimental parameters such as pH of the electrolyte, applied current density, electrodeposition time and carrier strontium concentration were thoroughly investigated to arrive at a condition resulting optimal deposition of the ⁹⁰Sr/⁹⁰Y activity on the substrate. An optimized electrochemical procedure to prepare ~3.7 MBq (~0.1 mCi) of circular planar ⁹⁰Sr/⁹⁰Y sources commensurate with regulatory safety requirement has been the positive outcome.     

Sorption of uranium using silica gel with benzoylthiourea derivatives

Benzoylthiourea derivatives (N,N-diphenyl-N′-(3-methylbenzoyl)thiourea and diphenyl-N′-(4-methylbenzoyl)thiourea) were impregnated onto silica gel. The preconcentration of uranium(VI) from aqueous solution was investigated. Extraction conditions were optimized in batch method prior to determination by uv–visible absorption spectrometry using arsenazo(III). The optimum pH for quantitative adsorption was found as 3–7. Quantitative recovery of uranium (VI) was achieved by stripping with 0.1 mol L^?1 HCl. Equilibration time was determined as 30 min for 99% sorption of U(VI). Under optimal conditions, dynamic linear range of for U(VI) was found as 0.25–10 μg mL^?1. The relative standard deviation as percentage and detection limit were 5.0% (n = 10) for 10 μg mL^?1 U(VI) solution and 8.7 ng mL^?1, respectively. The method was employed to the preconcentration of U(VI) ions in soil and tap water samples.     

New approaches to reprocessing of oxide nuclear fuel

Dissolution of UO₂, U₃O₈, and solid solutions of actinides in UO₂ in subacid aqueous solutions (pH 0.9–1.4) of Fe(III) nitrate was studied. Complete dissolution of the oxides is attained at a molar ratio of ferric nitrate to uranium of 1.6. During this process actinides pass into the solution in the form of U(VI), Np(V), Pu(III), and Am(III). In the solutions obtained U(VI) is stable both at room temperature and at elevated temperatures (60 °C), and at high U concentrations (up to 300 mg mL^?1). Behavior of fission products corresponding to spent nuclear fuel of a WWER-1000 reactor in the process of dissolution the simulated spent nuclear fuel in ferric nitrate solutions was studied. Cs, Sr, Ba, Y, La, and Ce together with U pass quantitatively from the fuel into the solution, whereas Mo, Tc, and Ru remain in the resulting insoluble precipitate of basic Fe salt and do not pass into the solution. Nd, Zr, and Pd pass into the solution by approximately 50 %. The recovery of U or jointly U + Pu from the dissolution solution of the oxide nuclear fuel is performed by precipitation of their peroxides, which allows efficient separation of actinides from residues of fission products and iron.     

Determination of As(III) and As(V) in water samples by flow injection online sorption preconcentration coupled to hydride generation atomic fluorescence spectrometry

A method was developed for the determination of arsenite [As(III)] and arsenate [As(V)] in water samples using flow injection online sorption coupled with hydride generation atomic fluorescence spectrometry (HG-AFS) using a cigarette filter as the sorbent. Selective determination of As(III) was achieved through online formation and retention of the pyrrolidine dithiocarbamate arsenic complex on the cigarette filter, but As(V) which did not form complexes was discarded. After reducing As(V) to As(III) using L-cysteine, total arsenic was determined by HG-AFS. The concentration of As(V) was calculated by the difference between As(III) and total arsenic. The analytes were eluted from the sorbent using 1.68 mol L^?1 HCl. With consumption of 22 mL of the sample solution, the enrichment factor of As(III) was 25.6. The detection limits (3σ/k) and the relative standard deviation for 11 replicate determinations of 1.0 ng mL^?1 As(III) were found to be 7.4 pg mL^?1 and 2.6%, respectively.     

Adsorption characteristics and radiation stability of a silica-based DtBuCH18C6 adsorbent for Sr(II) separation in HNO3 medium

A silica-based adsorbent, (DtBuCH18C6 + dodecanol)/SiO₂-P, which is used for selective separation of Sr(II) from high level liquid wastes, against temperature and gama-irradiation was investigated. The adsorption characteristics of Sr(II), Ba(II), La(III), Nd(III), Gd(III) and Dy(III) under varying nitric acid concentration at different temperatures were measured by batch method. The adsorbent showed higher distribution coefficients (K _d) for Sr(II) compared to other tested metal ions, and the K _d values of Sr(II) decreased with increasing temperature. Thermodynamic parameters of the adsorption process were calculated. The related parameters in adsorption isotherm models were obtained using a non-linear fitting. Uptake capacity from 0.38 to 0.43 mmol g^?1 was obtained for Sr(II) in the temperature range of 298–323 K by the Langmuir equation fitting. The leakage of total organic carbon was below 120 ppm at 298 K and 180 ppm at 323 K, respectively. The degradation of the adsorbent irradiated in 2 M HNO₃ was investigated. It is found that the adsorbed dose of γ-ray more than 50 KGy has a strong influence on K _d of Sr(II). The K _d values of Sr(II) decrease about 3 times ranged from 50 to 500 KGy.     

Separation and purification of 90Sr from PUREX HLLW using N,N,N′,N′-tetra(2-ethylhexyl) diglycolamide

This paper describes a method for the separation and purification of ⁹⁰Sr from PUREX–HLLW employing solvent extraction and precipitation techniques. 30 % TBP in n-dodecane was used for the removal of residual uranium, plutonium and neptunium from HLLW. Trivalent actinides and lanthanides were subsequently removed using N,N,N’,N’-tetra(2-ethylhexyl) diglycolamide (TEHDGA, 0.20 M in 30 % isodecyl alcohol and n-dodecane). ⁹⁰Sr was selectively extracted from actinides and lanthanides depleted HLLW using 0.3 M TEHDGA in 5 % isodecyl alcohol and dodecane. Loaded strontium was stripped using 0.01 M HNO₃ and further purified by radiochemical precipitation technique after adding Fe and natural strontium as carriers. Based on the experimental results, a flow-sheet was formulated and mCi levels of ⁹⁰Sr recovered.     

Synthesis of nano-pore size Al(III)-imprinted polymer for the extraction and preconcentration of aluminum ions

In this study, an ion imprinted polymer (IIP) was prepared for the selective separation and preconcentration of trace levels of aluminum. Al(III) IIP was synthesized in the presence of Al(III)-8-hydroxyquinoline (oxine) complex using styrene and ethylene glycol dimethacrylate as a monomer and crosslinker, respectively. The imprinted Al(III) ions were completely removed by leaching the IIP with HCl (50 % v/v) and were characterized by FTIR and scanning electron microscopy. The maximum sorption capacity for Al(III) ions was found to be 3.1 mg g^?1 at pH 6.0. Variables affecting the IIP solid phase extraction were optimized by the univariable method. Under the optimized conditions, a sample volume of 400 mL resulted in an enhancement factor of 194. The detection limit (defined as 3 S _b/m) was found to be 1.6 μg L^?1. The method was successfully applied to the determination of aluminum in natural water, fruit juice and cow milk samples.