Solid phase extractive preconcentration of some actinide elements using impregnated carbon

Apricot stone shells were carbonized under certain chemical and thermal conditions, and the resulting charcoal was impregnated with oxalic and succinic acids of different concentrations. The sorbents were physically characterized and used for preconcentration of U(VI) and Th(IV) from acidified aqueous solutions. Batch equilibrium studies revealed that a quantitative preconcentration could be achieved at pH ∼2 for U(VI) and ∼1.3 for Th(IV). The equilibration time was up to 24 h for U(VI) and 40 min for Th(IV). The modified sorbent showed a superior extraction ability for U(VI) and Th(IV) with the mean distribution coefficients (K _d) of 2084 and 7808 ml g⁻¹, respectively. The sorption capacity was found to be 2.39 and 8.47 mg g⁻¹ for U(VI) and Th(IV) on apricot stone anchored with oxalic acid and 2.3 and 9.18 mg g⁻¹ for the sorbent anchored with succinic acid, respectively. Desorption of the loaded uranium ions was effectively achieved using 1 M HNO₃, whereas only 0.5 M HNO₃ was recommended to release the retained thorium ions. Published in Russian in Radiokhimiya, 2008, Vol. 50, No. 1, pp. 50–56. The text was submitted by the authors in English.     

Solid-phase extractants based on taunit carbon nanotubes for actinide and REE preconcentration from nitric acid solutions

The sorption properties of solid-phase extractants (SPEs) prepared by impregnation of Taunit carbon nanotubes with adducts of diphenyl(dibutylcarbamoylmethyl)phosphine oxide (CMPO) and tri-n-octylphosphine oxide (TOPO) in HNO₃ solutions were studied. The SPEs exhibit high ability to sorb U(VI), Pu(IV), Np(V), Am(III), and Eu(III) from nitric acid solutions, with good kinetic properties. The impregnation conditions and distribution coefficients of the radionuclides in their recovery from 3 M HNO₃ were determined. The possibility of preparing SPEs by Taunit impregnation in HNO₃ solutions with adducts of tributyl phosphate (TBP) and N,N′-dimethyl-N,N′-dioctylhexylethoxymalonamide (DMDOHEMA) and with Cyphos IL-101 phosphonium ionic liquid was demonstrated.     

Calculated thermal expansion of the actinide elements

The linear thermal expansion coefficient is calculated for the early actinides thorium, protactinium, uranium, neptunium, and plutonium for a hypothetical fcc crystal structure. The relativistic spin-orbit interaction is included in these calculations. We show that the spin-orbit splitting of the 5f band gives rise to a considerable increase in the thermal expansion and, to a large extent, explains the anomalously large thermal expansion for these elements.Paper presented at the Tenth International Thermal Expansion Symposium, June 6–7, 1989, Boulder, Colorado, U.S.A.     

Ligand-assisted extraction for separation and preconcentration of gold nanoparticles from waters

A new two-step extraction procedure is proposed for separation and preconcentration of gold nanoparticles (Au-NPs) from aqueous samples. First, Au-NPs are loaded onto a reversed phase C-18 (RP-C18) column, and then ligand-assisted extraction into chloroform is performed. 1-Dodecanethiol (1-DDT, 5 mM) was used as selective ligand for quantitative extraction under ultrasonic condition. Parameters of the extraction procedure, such as sample volume, organic solvent, concentration and nature of the ligand, ultrasonication time, pH of the sample, and different coating as well as sizes of Au-NPs were investigated in regard to the extraction efficiency of Au-NPs. The optimized procedure allows separation and preconcentration of the Au-NPs with an enrichment factor of up to 250 assuring no changes in size and/or shape of the NPs. This was proved by investigation of the particles by UV-vis spectrometry and transmission electron microscopy (TEM). Furthermore, the presence of potentially interfering other metal nanoparticles (M-NPs) and dissolved organic matter (DOM) was studied. Observed minor recoveries of Au-NPs in DOM model solutions were overcome by hydrogen peroxide pretreatment up to a DOM concentration of about 4 mg/L. Feasibility of the proposed method was proved by application of the optimized procedure to 5 real water samples. Recoveries of Au-NPs in the real waters spiked in a concentration range from 0.15 to 5100 μg/L obtained by this method varied from 68.4% to 99.4%. Consequently, the proposed approach has great potential for the analysis of M-NPs in environmental waters.     

Quantitative enzyme-linked immunosorbent assay for determination of polychlorinated biphenyls in environmental soil and sediment samples

An enzyme-linked immunosorbent assay (ELISA) for the quantitative determination of Aroclors 1242, 1248, 1254, and 1260 in soil and sediments was developed and its performance compared with that of gas chromatography (GC). The detection limits for Aroclors 1242 and 1248 in soil are 10.5 and 9 ng/g, respectively. The assay linear dynamic range is 50-1333 ng/g. Cross-reactivity of the assay with 37 structurally related potential cocontaminants in environmental soil samples was examined; none of the chlorinated anisoles, benzenes, or phenols exhibited >3% cross-reactivity, with <0.1% cross-reactivity being the norm. Soil spike recoveries of 107% and 104% were obtained for Aroclors 1242 and 1248, respectively, for a spike level of 5 mg/kg, with corresponding relative standard deviations of 14% and 17%. One hundred forty-eight environmental soil, sediment, and paper pulp samples, obtained from two EPA listed Superfund sites, were analyzed by ELISA and standard GC methods. Samples were extracted for ELISA analysis by shaking with methanol. Additional extractions of the same samples were performed either with supercritical carbon dioxide or by Soxhlet extraction with methanol. ELISA results for both the supercritical fluid and the Soxhlet extracts were in close agreement with the GC results, while the ELISA results for the methanol shake extracts were not. The data for the environmental samples demonstrated the capability of the ELISA to provide accurate results and reinforced the dependence of any detection method, including ELISA, on appropriate extraction procedures.     

Speciation of chromium in water samples with cloud point extraction separation and preconcentration and determination by graphite furnace atomic absorption spectrometry

A novel method has been developed for the speciation of chromium in natural water samples based on cloud point extraction (CPE) separation and preconcentration, and determination by graphite furnace atomic absorption spectrometry (GFAAS). In this method, Cr(III) reacts with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (PMBP) yielding a hydrophobic complex, which then is entrapped in the surfactant-rich phase, whereas Cr(VI) remained in aqueous phase. Thus, separation of Cr(III) and Cr(VI) could be realized. Total chromium was determined after the reduction of Cr(VI) to Cr(III) by using ascorbic acid as reducing reagent. PMBP was used not only as chelating reagent in CPE procedure, but also as chemical modifier in GFAAS determination of chromium. The detection limit for Cr(III) was 21 ng L(-1) with an enrichment factor of 42, and the relative standard deviation was 3.5% (n=7, c=10 ng mL(-1)). The proposed method has been applied to the speciation of chromium in natural water samples with satisfactory results.     

Coupled isotachophoretic preconcentration and electrophoretic separation using bidirectional isotachophoresis

We present a novel technique for coupling isotachophoretic preconcentration and electrophoretic separation using bidirectional isotachophoresis (ITP). Bidirectional ITP simultaneously sets up sharp ITP interfaces between relatively high- and low-mobility cations and high- and low-mobility anions. These two interfaces can migrate toward each other and be described as ion concentration shock waves. We here demonstrate a bidirectional ITP process in which we use the interaction of these anionic and cationic ITP shock waves to trigger a transformation from ITP preconcentration to electrophoretic separation. We use anionic ITP to focus anionic sample species prior to shock interaction. The interaction of the counter-propagating anionic and cationic ITP shocks then changes the local pH (and ionic strength) of the focused analyte zones. Under this new condition, the analytes no longer focus and begin to separate electrophoretically. The method provides faster and much less dispersive transition from ITP preconcentration to electrophoretic separation compared with traditional (unidirectional) transient ITP. It eliminates the need for intermediate steps between focusing and separation, such as manual buffer exchanges. We illustrate the technique with numerical simulations of species transport equations. We have validated our simulations with experimental visualization of bidirectional ITP zones. We then show the effectiveness of the technique by coupling ITP preconcentration and high-resolution separation of a 1 kbp DNA ladder via shock interaction in bidirectional ITP.     

The feasibility of electromagnetic actinide isotope separation in the European community

The production of actinide reference materials in the European Community depends in those cases in which electromagnetically enriched material is required on the supply from the USA Department of Energy/Oak Ridge National Laboratory (DOE/ORNL). A study carried out by the Central Bureau for Nuclear Measurements (CBNM) is based on the needs for actinide reference materials in the European Community (EC) as determined by a separate inquiry in 1977 and examines the conditions for the installation of an electromagnetic separation facility of appropriate size in the EC. From a compilation of all the information about the production, chemical purification and isotopic enrichment of all actinide nuclides needed in the EC those cases have been assessed for which the application of electromagnetic isotope separation is at present unavoided (but feasible with the glovebox technique). Base materials for this separation process are readily available within the EC with the exception of ²⁴⁴Pu. The production of ²⁴⁴Pu was experimentally studied and extrapolated to production scale. The use of this isotope as a spike material in mass spectrometric plutonium determination is shown to be uneconomic. An electromagnetic separator adapted in capacity to EC needs was designed. Special containments and facilities for handling the radioactive actinide elements are proposed. From the cost price of this facility and operational experience of a few EC laboratories the total running costs and the specific product costs for the EC needs are calculated.     

Zincon-modified activated carbon for solid-phase extraction and preconcentration of trace lead and chromium from environmental samples

A new method that utilizes zincon-modified activated carbon (AC-ZCN) as a solid-phase extractant has been developed for simultaneous preconcentration of trace Cr(III) and Pb(II) prior to the measurement by inductively coupled plasma optical emission spectrometry (ICP-OES). The separation/preconcentration conditions of analytes were investigated, including effects of pH, the shaking time, the sample flow rate and volume, the elution condition and the interfering ions. At pH 4, the maximum adsorption capacity of Cr(III) and Pb(II) onto the AC-ZCN were 17.9 and 26.7 mg g⁻¹, respectively. The adsorbed metal ions were quantitatively eluted by 1 mL of 0.1 mol L⁻¹ HCl. Common coexisting ions did not interfere with the separation. According to the definition of IUPAC, the detection limits (3σ) of this method for Cr(III) and Pb(II) were 0.91 and 0.65 ng mL⁻¹, respectively. The relative standard deviation under optimum condition is less than 3.5% (n = 8). The method has been applied for the determination of Cr(III) and Pb(II) in biological materials and water samples with satisfactory results.     

Use of modified sorbent for the separation and preconcentration of chromium species from industrial waste water

A simple and sensitive method based on solid phase extraction (SPE) on acetyl acetone modified XAD-16 has been established for separation of Cr (III) and Cr (VI) from and industrial water samples. Two forms of chromium showed different exchange capacities at different pH values, viz. Cr (III) selectively retained at pH 5-7 whereas Cr (VI) retained at pH 1. Hence complete separation of the two forms of chromium is possible. Retained species were eluted with 5 mL of 2 mol L(-1) HNO(3) and 2 mol L(-1) NaOH. The detection limit of 0.02 and 0.014 microg mL(-1) was achieved for Cr (III) and Cr (VI), respectively, with an enrichment factor of 100 and 140. Various kinetic and thermodynamic parameters were also determined. The metal ion concentration was measured by atomic Absorption Spectroscopy. The possible retention mechanism is also discussed. The method was successfully applied for the speciation of chromium in industrial water samples.     

Solid-phase extractants for radionuclide preconcentration and separation. New possibilities

A review of solid-phase extractants for radionuclide preconcentration and separation is presented. Examples of solid-phase extractants prepared by impregnation of various supports with compounds used in liquid extraction are considered. The possibilities of using carbon nanotubes and ionic liquids for preparing new solid-phase extractants are discussed. Experimental data on sorption recovery of actinides, europium, and palladium from nitric acid solutions with solid-phase extractants prepared by impregnation of carbon nanotubes and polymeric supports with ionic liquids and ligands are presented.     

Radioactivity levels in some sediment samples from Red Sea and Baltic Sea

Levels of 22?,22?Ra, 232Th, 21?Pb, 21?Po and ??K in sediments from four monitoring areas, El Hamraween and Ras El Behar (Red Sea, Egypt) and LL3A and JML (Baltic Sea, Finland), have been investigated using alpha and gamma spectrometry. The average activity concentrations were 238±4 Bq kg?1 (22?Ra), 215±11 Bq kg?1 (21?Pb) and 311±18 Bq kg?1 (21?Po) for El Hamraween area. In Ras El Behar area, the corresponding values were 16±0.4, 18±1 and 20±5 Bq kg?1, respectively. The activity concentrations for 22?Ra, 21?Pb and 21?Po (uranium series) in El Hamraween bottom sediment are much high compared with those in Ras El Behar area, which indicates the enhanced levels due to the activities of phosphate mining and shipment operations in El Hamraween area. Excluding the influence of phosphate mining activities, it can be concluded that the levels of radioactivity in Baltic Sea sediments are higher than those in Red Sea sediments.     

Penicillium digitatum immobilized on pumice stone as a new solid phase extractor for preconcentration and/or separation of trace metals in environmental samples

This study presents a column solid phase extraction procedure based on column biosorption of Cu(II), Zn(II) and Pb(II) ions on Penicillium digitatum immobilized on pumice stone. The analytes were determined by flame atomic absorption spectrometry (FAAS). The optimum conditions such as: pH values, amount of solid phase, elution solution and flow rate of sample solution were evaluated for the quantitative recovery of the analytes. The effect of interfering ions on the recovery of the analytes has also been investigated. The recoveries of copper, zinc and lead under the optimum conditions were found to be 97+/-2, 98+/-2 and 98+/-2%, respectively, at 95% confidence level. For the analytes, 50-fold preconcentration was obtained. The analytical detection limits for Cu(II), Zn(II) and Pb(II) were 1.8, 1.3 and 5.8 ng mL(-1), respectively. The proposed procedure was applied for the determination of copper, zinc and lead in dam water, waste water, spring water, parsley and carrot. The accuracy of the procedure was checked by determining copper, zinc and lead in standard reference tea samples (GBW-07605).     

Efficient preconcentration and determination of traces of aluminum ion using silica-bonded glycerol sorbent

A solid-phase extraction system was proposed for the determination of aluminum after preconcentration with glycerol-bonded silica gel. The method is rapid and efficient for the enrichment of aluminum ions at trace levels. Optimal sorption conditions were found for sorption and desorption of aluminum ions. The effects of diverse ions on the sorption and recovery of aluminum have been studied and it was shown that the selectivity of the sorption process was very good. A very satisfactory preconcentration factor of 500 was achieved by this method. The lowest concentration of aluminum ions for quantitative recovery was 2ngml(-1). The capacity of sorbent was 400microg per gram of sorbent. The method showed good reproducibility (R.S.D.=2.2% for n=7) and was applied to the determination of aluminum in mineral water, hair and green tea samples.     

Copper(II)-8-hydroxquinoline coprecipitation system for preconcentration and separation of cobalt(II) and manganese(II) in real samples

A separation-preconcentration procedure based on the coprecipitation of cobalt(II) and manganese(II) ions with copper(II)-8-hydroxquinoline system has been developed. The analytical parameters including pH, amount of copper(II) as carrier element, amount of 8-hydroxquinoline, sample volume, etc., was investigated for the quantitative recoveries of Co(II) and Mn(II). No interferic effects were observed from the concomitant ions which are present in real samples. The detection limits for analyte ions by three sigma criteria were 0.86microgL(-1) for cobalt and 0.98microgL(-1) for manganese. The validation of the presented preconcentration procedure was performed by the analysis of NIST SRM 2711 Montana soil and GBW 07605 Tea certified reference materials. The procedure presented was applied to the analyte contents of real samples including natural waters and some food samples with successfully analytical results.