Adsorption and desorption behavior of tetravalent zirconium onto a silica-based macroporous TODGA adsorbent in HNO3 solution

To understand the separation behavior of Zr(IV) in the partitioning process for high level liquid waste, a silica-based macroporous adsorbent (TODGA/SiO₂-P) was prepared by impregnating N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) into a macroporous silica/polymer composite particles support (SiO₂-P). Adsorption and desorption behavior of Zr(IV) from nitric acid solution onto silica-based TODGA/SiO₂-P adsorbent were investigated by batch experiment. It was found that TODGA/SiO₂-P showed strong adsorption affinity to Zr(IV) and this adsorption process reached equilibrium state around 6 h at 298 K. Meanwhile, HNO₃ concentration had no significant effect on the adsorption of Zr(IV) above 1 M. From calculated thermodynamic parameters, this adsorption process could occur spontaneously at the given temperature and was confirmed to be an exothermic reaction. This adsorption process could be expressed by Langmuir monomolecular layer adsorption mode and the maximum adsorption capacity were determined to be 0.283 and 0.512 mmol/g for Zr(IV) at 298 and 323 K, respectively. In addition, more than 90 % of Zr(IV) adsorbed onto adsorbent could be desorbed with 0.01 M diethylenetriamine pentaacetic acid solution within 24 h at 298 K.     

Adsorption behavior of Me2-CA-BTP/SiO2-P adsorbent toward MA(III) and Ln(III) in nitrate solution

A porous Me₂-CA-BTP/SiO₂-P adsorbent was prepared to separate MA(III) from Ln(III) in high level liquid waste (HLLW). The adsorption behavior of Me₂-CA-BTP/SiO₂-P toward ²⁴¹Am(III) and Ln(III) in 0.01 M HNO₃-NaNO₃ solution was studied. Me₂-CA-BTP/SiO₂-P showed high adsorption and selectivity toward ²⁴¹Am(III) over Ln(III) fission products with the separation factor (SF) reaching to 557, 2355, 1952, 1082, 214, 105, 86, 14 for Y, La, Ce, Nd, Sm, Eu, Gd and Dy respectively in 0.01 M HNO₃-0.99 M NaNO₃ solution. The adsorption kinetics of both Dy(III) and Eu(III) on Me₂-CA-BTP/SiO₂-P was studied and followed pseudo-second-order rate equation indicating chemical sorption as the rate-limiting step of the adsorption, and the adsorption isotherm of Dy(III) and Eu(III) matched better with the Langmuir isotherm than the Freundlich isotherm with the adsorption amount around 0.22 and 0.20 mmol/g respectively. Thermodynamic study revealed that the adsorption of both Dy(III) and Eu(III) on Me₂-CA-BTP/SiO₂-P was spontaneous and endothermic processes with a positive entropy at 298, 308, 313 K.     

Studies on adsorption and separation characteristics of americium and lanthanides using a silica-based macroporous bi(2-ethylhexyl) phosphoric acid (HDEHP) adsorbent

Activity concentrations of ⁹⁰Sr in samples of wild boar bones hunted in different regions of Slovakia were determined. Molecular recognition technology product IBC´s AnaLig^®Sr-01 and tributyl phosphate were used for strontium determination. From 7 to 10 g of bone ash was used for ⁹⁰Sr analysis. Both separation methods were statistical tested and compared. The presented results were evaluated as correct for all experimental data for ⁹⁰Sr determination in ash bone samples. Activity concentrations of ⁹⁰Sr in bones were in the range of (4.5–69.0) Bq kg^?1.     

Impregnation synthesis of a novel macroporous silica-based TODGA polymeric composite and its application in the adsorption of rare earths in nitric acid solution containing diethylenetriaminepentaacetic acid

A macroporous silica-based N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) polymeric composite (TODGA/SiO₂-P) was synthesized. It was done through impregnation and immobilization of TODGA molecule into the pores of the SiO₂-P particles utilizing a vacuum sucking technique. The macroporous SiO₂-P particles were the silica-based organic/inorganic composite synthesized by immobilizing styrene-divinylbenzene copolymer inside SiO₂ through the complicated polymerization reaction. The adsorption of rare earth (RE(III)) elements onto TODGA/SiO₂-P was investigated in HNO₃ solution containing diethylenetriaminepentaacetic acid (DTPA), an acidic multi-dentate chelating agent. It was found that in the presence of 0.05 M DTPA, and H⁺ had significant effect on the TODGA/SiO₂-P adsorption due to the competition reactions of RE(III) with different species, H₄DTPA⁻ and H₂DTPA³⁻. With an increase in the concentration of from 0.115 M to 3.015 M, the adsorption of RE(III) onto TODGA/SiO₂-P increased noticeably. On the other hand, RE(III) showed strong adsorption at 0.1 M H⁺, weak adsorption at around pH 2, and no adsorption in excess of pH 2.3. In a 0.1 M H⁺-0.115 M -0.05 M DTPA solution, a change of the distribution coefficient of RE(III) onto TODGA/SiO₂-P with an increase in atomic number of RE(III) from La(III) to Lu(III) was investigated. The silica-based TODGA/SiO₂-P polymeric composite showed strong adsorption for heavy RE(III) over the light one. In a 0.01 M H⁺-1.0 M -0.05 M DTPA solution, the effect of the ratio of solid phase to liquid one on the relationship of the distribution coefficient of RE(III) with the change in atomic number of RE(III) was also studied. Based on the complicated disassociation equilibrium of DTPA, the influence of the concentrations of and H⁺ on the adsorption of TODGA/SiO₂-P for RE(III) was demonstrated. This makes the partitioning of RE(III) and MA(III) together from high level liquid waste (HLLW) by the polymeric composite TODGA/SiO₂-P promising.     

Adsorption and separation behavior of strontium and yttrium using a silica-based CMPO adsorbent

Journal of Radioanalytical and Nuclear Chemistry - To separate Y(III) from a Sr(II)–Y(II) mixture, two silica-based adsorbents, CMPO/SiO2-P and (CMPO?+?Dodec)/SiO2-P were prepared...     

Adsorption behavior of Pd(II) ions from aqueous solution onto pyromellitic acid modified-UiO-66-NH2

A new adsorbent was successfully fabricated by chemically linking pyromellitic acid onto a zirconium-based metal-organic framework composite for selective adsorption of Pd(II) from an aqueous solution. The adsorbent was characterized by Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller equation and scanning electron microscope. The adsorption capacity, selectivity and repeatability of the adsorbent were tested by batch experiments. The optimum pH was 2.0, and the maximum adsorption capacity at room temperature was 226.1 mg/g. In the kinetic experiments, the adsorption process achieved equilibrium within 5 h and generally conformed to the quasi-second kinetics and Freundlich isotherm model. The N-H and OH groups on the adsorbent interacted with Pd(II) by electrostatic and coordination action. The adsorbent maintained excellent adsorption capacity after at least 5 cycles. At the same time, the selectivity of the adsorbent in aqueous solution is excellent from interfering ions. Therefore, the new adsorbent will have an obvious application prospect on the recovery of palladium.     

Optimizing composition of TODGA/SiO2-P adsorbent for extraction chromatography process

As a part of developing extraction chromatography technology for minor actinides (MA(III); Am and Cm) recovery from spent fast reactor fuels, improvement on the TODGA/SiO2-P adsorbent to enhance its desorption efficiency was carried out. Batchwise adsorption/elution experiments showed that optimizations in amount of the extractant impregnated in the support of the SiO2-P which is the porous silica coated with polymer and degree of the cross linkage of polymer succeeded in finding the optimum values. Inactive column separation experiments with the simulated high level liquid waste and the optimized adsorbent revealed that decontamination factors of fission products can also be improved as well as the recovery yields.     

Adsorption and separation behavior of strontium and yttrium using a silica-based bis(2-ethylhexyl) hydrogen phosphate adsorbent

Journal of Radioanalytical and Nuclear Chemistry - (HDEHP?+?Hexa)/SiO2-P, a silica-based adsorbent, was prepared and used to separate Y(III) from a mixed solution of Sr(II) and Y(III)....     

The stability sequence of the trivalent rare earth chelates of 2-nitroso-1-naphthol-8-sulphonic acid in aqueous solution

A method is described for estimating the concentration of di(n-octyltin) bis-maleate in five food-simulating solvents recommended by the United States Food and Drug Administration for migration studies on food containers. Atomic absorption spectrometry with electrothermal atomization provides a detection limit of 0.01 ppm tin stabilizer in the food simulators. Both calibration curve and standard addition methods were employed to check for possible matrix effects. Analysis time was less than 90 s per sample. Ethanol solutions were difficult to analyze because of residual inorganic tin blanks, presumably arising from the ethanol container. Water, acetic acid and heptane were free of residual tin blanks. Amounts of tin stabilizer extracted from several different resins ranged from 0.01 to 0.18 ppm.     

Adsorption of metal ions from solution onto a piezoelectric quartz crystal

Many metal ions are spontaneously adsorbed onto a piezoelectric quartz crystal and change the oscillation frequency. The pH ranges in which the metal ions adsorbed were just below that of precipitate formation as the ‘hydroxides’; frequency changes caused by adsorption were not observed in these pH ranges where the ‘hydroxides’ formed. Cationic organic reagents, such as crystal violet and methylene blue, were also adsorbed on the piezoelectric quartz crystal but non-ionic and anionic organic compounds were not. These results showed that the crystal was negatively charged on the surface.     

Infrared and Raman spectroscopic and theoretical studies of nonaaqua complexes of trivalent rare earth metal ions

Infrared (IR), far-infrared (far-IR) and Raman spectra have been recorded of the hydrated lanthanide(III) trifluoromethanesulfonates, [Ln(OH2)9](CF3SO3)3, (Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), and also for the deuterated [La(OD2)9](CF3SO3)3 compound. This has enabled complete assignments of all seven metal-oxygen stretching modes for the first time. Force constant calculations have been performed for an LnO9(3+) moiety, with a tricapped trigonal prismatic oxygen atom arrangement in D3h point group symmetry. The lanthanide contraction in reflected in continuously increasing trends for the averaged LnO stretching frequencies and force constants with increasing inverse of ionic radii. The stretching force constants increased from 0.81 to 1.16 Ncm-1 for the LnO6 prism in the series from La to Lu, while those for the capping LnO3 bonds increased from 0.49 to 0.65 Ncm-1. The LnO stretching force constants showed a smooth correlation with the LnO bond distances to the prism oxygen atoms, while the correlation to the LnO capping oxygen atoms has a different shape, reflecting the increased ligand-ligand repulsion with decreasing lanthanide ion size.     

Electrochemical reduction of americium and some rare earth elements in acetonitrile

The electrochemical reduction of americium, thulium, erbium, samarium and europium has been investigated in acetonitrile. Am, Tm and Er, like Eu and Sm, have been suggested to be converted to the divalent state during the reduction. The divalent cations are oxidized at different rates by water that is present in the solvent to form the hydrolyzed trivalent ions. Their reduction is completed by precipitation of basic salts. Stability of the divalent cations to oxidation by water determines the extent of the transference of these elements to the amalgam and to the basic salt precipitate.     

利用荧光浓度指示剂fura-2研究稀土离子的跨膜行为

本文提出了利用fura-2测量细胞内游离稀土离子浓度的定量方法。实验结果表明, 在模拟细胞内离子组成的条件下, 稀土离子La^3^+和Y^3^+与fura-2形成1:1的配合物。其配合物的表观离解常数分别为161nmol.dm^-^3和404nmol.dm^-^3,pH7.05, 有未配对f电子的Nd^3^+, Ho^3^+, Sm^3^+, Dy^3^+,Ce^3^+, Yb^3^+等稀土离子对荧光起萃灭作用。此性质使我们能够定性鉴定它们是否进入了细胞。我们使用如上性质, 利用单细胞阳离子测试系统, 以小鼠骨髓瘤细胞为模式细胞, 研究了上游离稀土离子的跨膜行为及部分体内小分子对稀土离子跨膜行为的影响。实验结果支持游离稀土离子不能通过细胞膜的假设, 而且所研究的体内小分子在生理浓度下对稀土离子的跨膜也无明显作用。     

Raman spectroscopic study on the coordination behavior of rare earth ions in N-methylacetamide

The coordination behavior of rare earth (Ln (3+)) ions in N-methylacetamide (NMA) solution has been investigated at room temperature by Raman spectroscopy. The behavior of the symmetric Raman Ln-Cl stretching (nu Ln-Cl) band, and amide I (nu AI), and III (nu AIII) bands of NMA with the rare earth series is discussed in conjunction with the change in the coordination structure occurring in the middle of the rare earth series. A competition for a coordination equilibria between a Cl (-) ion and an NMA molecule from the rare earth chloride-NMA complex might occur in the middle rare earth region. It is demonstrated that the change in the coordination structure of Ln (3+) ions in NMA is due to an elimination of an NMA molecule.     

Luminescence of vanadium and rare earth ions in alkaline earth sulfates

The luminescence of samples MeSO₄V, RE (Me = Mg, Ca, Ba) depends strongly on the nature of the Me ions. The amount of association of the V⁵⁺ and RE³⁺ ions can be estimated from the measured quantum efficiencies.     

Evaluation study on properties of isohexyl-BTP/SiO2-P resin for direct separation of trivalent minor actinides from HLLW

In order to develop a direct separation process for trivalent minor actinides from fission products in high level liquid waste (HLLW) by extraction chromatography, a novel macroporous silica-based 2,6-bis(5,6-diisohexyl)-1,2,4-triazin-3-yl)pyridine resin (isohexyl-BTP/SiO₂-P resin) was prepared. The content of isohexyl-BTP extractant in the resin was as high as 33.3 wt%. The resin exhibited much higher adsorption affinity for Am(III) in 2–3 M (mol/L) HNO₃ solution over U and FP which are contained in HLLW. The kinetic data were analyzed using pseudo-second-order equation. The results suggested that the Eu(III), Gd(III), and Dy(III) adsorption was well explained by the pseudo-second-order equation. Quantitative desorption for adsorbed elements was achieved by using H₂O or thiourea as eluting agents. However, the kinetics of adsorption and desorption were rather slow and this drawback needs to be resolved. Stability of the resin against HNO₃ was also examined. It was found that the resin was considerably stable against ≤4 M HNO₃ solution for the reasons of an extremely small leakage of the extractant into the solution from the resin and the adsorption performance keeping for rare earths in 3 M HNO₃ solution.     

Adsorption and separation behaviors of molybdenum from high-level liquid waste using a silica-based hydroxyoxime impregnated adsorbent

Journal of Radioanalytical and Nuclear Chemistry - To separate Mo(VI) from high-level liquid waste, a silica-based (anti-DEHDO + Dodec)/SiO2-P adsorbent was synthesized by impregnating...