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- Author or Editor: A. Paulenová x
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Abstract
This paper presents the application of a new sensor materials, whichcombine extraction chromatography and scintillation detection. The resultantsensor embodies the simultaneous dual functionality of selective extractionand radiation detection, which has been applied towards off-line and on-linemonitoring of radiostrontium in aqueous solutions. The sensor materials are(1) a mixture of commercially available Sr-selective extraction chromatographicresin and granular scintillator, (2) bis-4,4'(5')-tert-butylcyclohexano-18-crown-6(DtBuCH18C6) in 1-octanol coated on the surface of a scintillating glass and(3) inert chromatographic resin impregnated with the organic fluors, 2,5 diphenyloxazole,(PPO) and 1-4 bis(4- methyl-5-phenyloxazol-2-yl) benzene, (DM-POPOP) and eitherDtBuCH18C6 in 1-octanol or a proprietary extractant. For off-line measurements,the sensor materials are used in the same manner as the commercially availableextraction chromatographic resin, but rather than eluting the activity fromthe column, the scintillating extraction column is placed in a scintillationvial and counted without the introduction of liquid scintillation cocktail.For on-line measurements, the sensor materials are used in conjunction witha flow-cell scintillation detection system to assess the activity retainedby the extractant in real-time. Characterization of the detection efficiencyand regeneration capability of the extractive scintillator materials is evaluated.
Abstract
The preconcentration of strontium from aqueous colloid solution containing di(2-ethylhexyl)-phosphoric acid as a surfactant was performed using micellar ultrafiltration technique. Filters with different pore size and materials (nitrocellulose, polysulfonate, glass fibers) were used to achieve a separation from liquid solutions. The strontium recoveries depending on the different conditions (pH, concentration of surfactant, background electrolytes) were determined and the results are explained in the terms of colloidal parameters of the system, viz. surface tension and turbidity.
Abstract
The preconcentration of strontium using a solid phase separation technique with selective micelle forming complexant has been studied. Di-2-ethylhexylphosphoric acid and its thio- and dithio derivatives were used as modifiers. The goal of this work was to study the influence of physico-chemical parameters on recovery of strontium after its preconcentration on reverse phase (Si–C-18) using micelle modifiers.
Abstract
Standard Gibbs energies of transfer of cesium ion from water to nitrobenzene and nitrobenzene-carbon tetrachloride mixture have been evaluated from electrochemical measurements. From the results the conclusion can be drawn that with increasing dielectric permitivity of organic mixed solvents the value of the Gibbs transfer energy of Cs+ ion decreases.
Abstract
Th anionic micellar system of the sodium dodecylsulphate (SDS) with di-2-ethylhexylphosphoric acid (D2EHPA) chelating ligand reagent in acctate buffer solutions was studied. The influence of the concentration and the composition of the micellar system for strontium preconcentration was determined. Different pH values of solutions as well as different concentration ratios of the ligand to the surfactant were used.
Abstract
The ultrafiltration preconcentration of Cd2+ using micellar extraction with 8-hydroxyquinoline (8-HQ), solubilized in anionic micelles of sodium dodecylsulphate (SDS)) were studied. The n-butanol was used as a co-surfactant. Ultrafiltration yields (R, %) on cellulose acetate membranes (wet, 20000 MW-CO) under 400 kPa pressure were determined. Distribution ratios (D) of cadmium between bulk liquid phase and micellar pseudophase were estimated. The constants (app.) for the cadmium-sodium exchange on SDS micelles surface at pH values of 4.8 and 5.3 (3.36 and 3.86, respectively) were determined. It was found, that the values of ultrafiltration yields of the cadmium (at constant concentration of 8-HQ) are influenced not only by the pH and by the concentration values, but also by the ratio of the concentrations of the metal and the anionic surfactant.
Abstract
A system using an ion chromatograph coupled to a flow-cell scintillation detector for rapidly measuring the oxidation states of actinides at low concentrations (<10–6M) in aqueous solutions was evaluated. The key components of the system are a cation–anion separation column (Dionex, CS5) and a flow cell detector with scintillating cerium activated glass beads. The typical procedure was to introduce a 0.5 ml aliquot of sample spiked with actinides in the +III to +VI oxidation states into a 5 ml sample loop followed by 4 ml of synthetic groundwater simulant. Separation was achieved at a flow rate of 1 ml/min using an isocratic elution with oxalic, diglycolic, and nitric acids followed by distilled water. Tests were first conducted to determine elution times and recoveries for an acidic solution (pH 
2) and a ground water simulant (pH 8) containing Am(III), Pu(IV), Th(IV), Pu(V), and U(VI). Then, an analysis was performed using a mixture of Pu(IV), Pu(V), and Pu(VI) in the ground water simulant and compared to results using the DBM extraction technique. Approximate elution times were the same for both the acidic solution and the ground water simulant. These were as follows: Pu(V) at 10 min, Am(III) at 15 min, Pu(IV) at 25 min, Th (IV) at 28 min and U(VI) at 36 min. Recoveries for the acidic solution were quantitative for U(VI) and Th(IV) and exceeded 80% for Am(III). Recoveries for the ground water simulant were quantitative for U(VI), but they were generally not quantitative for Th(IV), Pu(IV), and Am(III). For Th(IV) and Pu(IV), less than quantitative recoveries were attributed to the formation of neutral hydroxides and colloids; for Am(III) they were attributed to insoluble carbonates and/or hydroxycarbonates. When applied to the measurement of plutonium in the ground water simulant, the technique provided showed good agreement with the dibenzoylmethane (DBM) extraction technique, but it could not distinguish between Pu(V) and Pu(VI). This was likely due to the reduction of Pu(VI) to Pu(V) in the sample by the oxalic acid eluent. However, in spite of this limitation, the technique can be used to distinguish between Pu(IV) and Pu(V) in aqueous environmental samples within a pH range of 4 to 8 and an E
H range of -0.2 to 0.6 V, the predominance region for Pu(III), (IV), and (V). In addition, this technique can be used to corroborate oxidation state analysis from the dibenzoylmethane (DBM) extraction method for environmental samples.
Abstract
The preconcentration of cadmium from aqueous colloid solution containing 8-hydroxyquinoline as extractant, laurylsulphate natrium as surfactant,n-butanol as co-surfactant was performed using micellar ultrafiltration technique. Filters with different pore size and materials were used to achieve a separation from liquid solutions. The cadmium recoveries depending on different conditions (pH, concentration of surfactant) were determined and the results are explained in the terms of colloidal parameters in the compare with the classical solvent extraction.
Abstract
The advanced separation extraction process based on tri-n-butyl phosphate organic phase called UREX is being developed to separate uranium from fission products and other actinides, and the acetohydroxamic acid (AHA) is employed to reduce and complex plutonium and neptunium in order to decrease their distribution to the TBP-organic phase. In this study, the extraction of uranium was performed from various aqueous matrices with different concentrations of HNO3, LiNO3, and AHA. Extraction of uranium increases with increasing both initial HNO3 and total nitrate concentration. UV-VIS spectrophotometry confirmed that AHA is involved in the complex of uranium with TBP.
Abstract
There was a significant research progress achieved with the aim to modify conventional PUREX process by stripping of plutonium from the tri-n-butyl phosphate (TBP) extraction product in the form of non-extractable complexes upon addition of back-hold complexation agents. The present paper reports effects of such salt-free complexant, acetohydroxamic acid (HAHA), on distribution ratio of Pu(IV) under wide concentration of nitric acid and additional nitrate. General formula of plutonium species present in the organic phase can be described as Pu(OH)x(AHA)y(NO3)4−x−y·2TBP·wHNO3.
