Complexation of Eu3+ and Am3+ with soil humic acid extracted from Okchon Basin of Korean Peninsula

The complexation of Eu³⁺ and Am³⁺ ions with the humic acids has been investigated at various pH (4.0, 4.5, 5.0, 5.4) in 0.1M NaClO₄ solution using solvent extraction technique. Two humic acids are used in this study: humic acid extracted from the soil of Taejon on the Okchon Basin of Korea (TJHA) and commercially available one from Aldrich Chemical Co. (AHA). The total carboxylate group concentrations were determined to be 3.58 meq/g and 4.59 meq/g for Taejon and Aldrich humic acids, respectively. The conditional stability constants (log ₁ and log ₂), dependent on the pH of the solution, of the complexes of Eu³⁺ and Am³⁺ ions with the humic acids have been determined at the ionic medium of 0.1M NaClO₄. The values of stability constants with the degree of ionization of TJHA for Eu and Am complexes are quite well agreed with those of Lake Bradford humic acid (LBHA), indicating that structural characteristics of TJHA and LBHA may be quite similar to one another.     

Extraction chromatographic study on the separation of Am<Superscript>3+</Superscript> and Eu<Superscript>3+</Superscript> using ethyl-BTP as the extractant

Ethyl-substituted bis-triazinylpyridine (Et-BTP), a nitrogen containing soft-donor extractant, was used in investigations pertaining to the separation of Am³⁺ and Eu³⁺ from dilute nitric acid feed solutions by extraction chromatography using XAD-4 as the inert support, chlorinated dicarbollide as the modifier and 2-nitrophenyloctylether (NPOE) as the diluent. After carrying out a series of experiments, the optimum composition of the extractant mixture for the resin was found out to be 0.1 M Et-BTP and 0.025 M CCD in NPOE. Separation factor values were encouraging to carry out subsequent batch uptake studies at varying nitrate ion concentration which indicated favourable separation behaviour up to NaNO₃ concentration of 2 M. Column studies have been carried out and conditions for elution and separation of Am³⁺ from Eu³⁺ have been found out. Long term stability of the resin was also investigated.     

On the complex of humic acid – Am3+

It is suggested that Am³⁺ is forming different complexes with humic acids. At pH 4–5 at low concentration of Am³⁺ the complex is water soluble, while at higher concentration of Am³⁺ an insoluble complex is formed.     

Extraction of Americium(III) and Europium(III) with Two Open-Chain Crown Ethers of Amide Type

The extraction of Am³⁺ and Eu³⁺ from aqueous picric acid solution by N, N-dinaphthyl-N, N-diphenyl-3,6-dioxaoctanediamide (L^I) and 1, 1-(3, 6, 9-trioxaundecanedionyl)diphenothiazine (L^II) was investigated by a radioactive tracer technique. Extraction distribution ratios of Am³⁺ and Eu³⁺ have been measured as a function of pH, picric acid concentration, extractant concentration, diluent and temperature. The extraction of Am³⁺ is preferred to that of Eu³⁺ for both L^I and L^II, and the latter gives larger separation factor than the former. The equilibrium constants and thermodynamic parameters of extraction reactions were also calculated.     

Extraction of microamounts of europium and americium by using hydrogen dicarbollylcobaltate in the presence of dibutyl diethylcarbamoylmethylene phosphonate

Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of dibutyl diethylcarbamoylmethylene phosphonate (DBDECMP, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, HL₂²⁺ ML₃³⁺ and ML₄³⁺ (M³⁺ = Eu³⁺, Am³⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

Tremendous impact of substituent group on the extraction and selectivity to Am(III) over Eu(III) by diaryldithiophosphinic acids: experimental and DFT analysis

Comparative extraction of Am³⁺ over Eu³⁺ from nitric acid media by three dithiophosphinic acids (L) bearing different substituent aryl groups was studied. Within the experimental pH range, the distribution ratio of Am³⁺ and Eu³⁺ increases with the increase of pH due to deprotonation of the acidic extractant. Both the extraction and separation ability toward Am³⁺/Eu³⁺ by these extractants were affected drastically by the substituent aryl groups. The bis-phenyl substituted extractant shows almost no ability to extract and separate Am³⁺ from Eu³⁺, while bis(ortho-trifluoromethylphenyl) dithiophosphinic acid has the optimum extraction and separation capabilities. To help reveal the complexation and extraction behavior, the structure and bonding characters of neutral ML₃ (M?=?Am or Eu) complexes as well as the biphasic extraction reaction were studied by density functional theory (DFT). The conduct-like screening model implicit solvation model was used to simulate the extraction reaction in the aqueous-toluene biphasic system. The calculated sequence of the Gibbs free energy difference of extraction (ΔΔG ^Am/Eu_ext ) is consistent with the experimental results.

     

Scalar Relativistic Density Functional Theoretical Investigation of Higher Complexation Ability of Substituted 1,10‐Phenanthroline over Bipyridine Towards Am3+/Eu3+ Ions

The better selectivity of Am³⁺ over Eu³⁺ ion with N‐based CyMe4‐BTPhen compared to CyMe4‐BTBP for experimentally observed [ML₂(NO₃)]²⁺ complexes was demonstrated using scalar relativistic DFT in conjunction with Born‐Haber thermodynamic cycle and COSMO solvation model. The calculated free energy of extraction, ΔG_ext reveals strong dependence on the hydration free energies of Am³⁺ and Eu³⁺ ions and week dependence to the difference in Gibbs free energy of solvation of the ligand or metal‐ligand complexes. Further, for the first time, we have computed the effect of co‐anion species ([M(NO₃)₅]^2–) on ΔG_ext of Am³⁺ and Eu³⁺ ions with CyMe4‐BTPhen and CyMe4‐BTBP, which adds a positive contribution and thus reduces the ΔG_ext. The calculated values of ΔΔΔG_ext (= ΔΔG_ext,L1 – ΔΔG_ext,L2, ΔΔG_ext = ΔG_ext,M1 – ΔG_ext,M2) can be used to avoid the very sensitive metal ion solvation energy, effect of co‐anionic species and thus provides a robust approach to determine the selectivity between two metal ions towards different competitive ligands. The natural population analysis (NPA), molecular orbital analysis, Mayer bond order analysis, and bond character analysis using Bader's quantum theory of atoms in molecules indicates slightly more covalency for complexes of Am³⁺ ion that are correlated to the experiental selectvity of Am³⁺ ion over Eu³⁺ ion and hence might be useful in the design and development of next generation extractants.     

Extraction of microamounts of europium and americium into nitrobenzene by using hydrogen dicarbollylcobaltate in the presence of diphenyl-N-butylcarbamoylmethyl phosphine oxide

Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of diphenyl-N-butylcarbamoylmethyl phosphine oxide (DPBCMPO, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, HL₂⁺, ML₂³⁺, ML₃³⁺ and ML₄³⁺ (M³⁺ = Eu³⁺, Am³⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It has been found that the stability constants of the corresponding complexes EuL _n ³⁺ and AmL _n ³⁺, where n = 2, 3, 4 and L is DPBCMPO, in water saturated nitrobenzene are comparable.     

Extraction of tri- and tetravalent actinides with dihexyl N,N-diethylcarbamoylmethyl phosphonate (DHDECMP) and TBP from nitric acid solutions

Extraction of trivalent (Pu³⁺, Am³⁺, actinides and Eu³⁺, a representative of lanthanides) and tetravalent (Np⁴⁺ and Pu⁴⁺) actinides has been studied with dihexyl N,N-di-ethylcarbamoylmethyl phosphonate (DHDECMP) in combination with TBP in benzene from 2M nitric acid. The stoichiometries of the species extracted were found to be M(NO₃)₃·(3–n) TBP·n DHDECMP (for trivalent ions) and M(NO₃)₄·(2–n) TBP·n DHDECMP (for tetravalent ions) by the slope ratio method. The extraction constants evaluated (from the distribution data) indicate that for tetravalent ions (with solvation number two) the extraction constant increases when TBP (Kh=0.17) molecules are successively replaced by more basic DHDECMP (Kh=0.34) molecules. However, for trivalent ions (with solvation number three) when TBP molecules are totally replaced by DHDECMP molecules stereochemical factors appear and instead of increase, a substantial decrease in extraction constants is observed for Eu³⁺ and Am³⁺, a lesser decrease being observed for Pu³⁺ (larger ion).     

Structural influences on the lanthanide-actinide selectivity of some aminocarboxylates

Data for the resolution of americium from europium and terbium using 2,2′-diaminodiethylether-N,N,N′,N′-tetraacetate and 1,5-diaminopentane-N,N,N′,N′-tetraacetate are reported along with values of the formation constants of the La-Lu and Y chelates of the latter. It is shown that the minimum single-stage separation factor for Am³⁺ from Ln³⁺ cations, using 2,2′-diaminodiethylether-N,N,N′,-N′-tetraacetate with Dowex 50 resin, exceeds 1.7 for all Am-Ln pairs, and runs as high as 350 in the case of Am³⁺, La³⁺. The minimum of 1.7 occurs at Eu³⁺ in the lanthanon sequence. A novel separation of Am³⁺, Cm³⁺ and heavier actinons from each other and from all the lanthanons and yttrium appears to be feasible.     

Eu3+ concentration dependent optical properties and energy transfer from host Gd3+ to Eu3+ in GdF3 nanocrystals

By using a hydrothermal method, a series of Eu³⁺ concentration dependent GdF₃ nanocrystals have been synthesized. The crystalline structures of samples are characterized by XRD patterns, the morphology and size of the samples are illustrated by FE-SEM images, and the optical properties of the samples are presented by PL excitation and emission spectra. The energy transfer from host Gd³⁺ to Eu³⁺ is observed in the Eu³⁺ doped GdF₃ nanocrystals. The optical properties of Eu³⁺ and the energy transfer efficiency from host Gd³⁺ to Eu³⁺ are discussed on the basis of the Eu³⁺ concentration dependent integrated PL excitation and emission spectra of Gd³⁺ and Eu³⁺. The discussion on optical properties of Eu³⁺ and the energy transfer from Gd³⁺ to Eu³⁺ is meaningful to design and synthesize Gd³⁺ based compounds.     

Extractive distribution of microamounts of europium and americium in the two phase water — HCl — nitrobenzene — N,N,N′,N′-tetraethyl-2,6-dipicolinamide — hydrogen dicarbollylcobaltate system

Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of N,N,N′,N′-tetraethyl-2,6-dipicolinamide (TEtDPA, L) has been investigated. The equilibrium data have been explained assuming that the cations HL⁺, HL₂³⁺, ML₂³⁺ and ML₃³⁺ (M³⁺ = Eu³⁺, Am³⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It has been found that the stability constants of the corresponding complexes EuL _n,org³⁺ and AmL _n,org³⁺, where n = 2, 3 and L is TEtDPA, in the mentioned medium are comparable.     

Synergistic extraction of europium and americium into nitrobenzene by using hydrogen dicarbollylcobaltate and 1,2-(diphenylphosphino)ethane dioxide

Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of 1,2-(diphenylphosphino)ethane dioxide (DPPEtDO, L) has been investigated. The equilibrium data have been explained assuming that the species HL⁺, HL₂ ⁺, ML₂ ³⁺ and ML₄ ³⁺ (M³⁺ = Eu³⁺, Am³⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that the stability constants of the corresponding complexes EuL _n ³⁺ and AmL _n ³⁺, where n = 2, 4 and L is DPPEtDO, in water-saturated nitrobenzene are comparable.     

Rare earth complexes chemiluminescence catalyzed by gold nanoparticles for fast sensing of Tb3+ and Eu3+

Developing multiplex sensing technique is of great significance for fast sample analysis. However, the broad emissions of most chemiluminescence(CL) luminophores make the multiplex CL analysis be difficult. In this work, a simple and sensitive CL analytical method has been developed for the simultaneous determination of Tb³⁺and Eu³⁺thanking to their narrow band emission. The technique was based on a mixed CL system of periodate(IO₄^-)-hydrogen peroxide(...     

Extraction of microamounts of europium and americium into nitrobenzene by using hydrogen dicarbollylcobaltate in the presence of N,N′-dibutyl-N,N′-dimethyl-2-(2-dodecyloxyethyl)-malonamide

Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻¹) in the presence of N,N′-dibutyl-N,N′-dimethyl-2-(2-dodecyloxyethyl)-malonamide (DBDMDDOEMA, L) has been investigated. The equilibrium data have been explained assuming that the cations HL₂⁺, ML₂³⁺ and ML₃³⁺ (M³⁺ = Eu³⁺, Am³⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It has been found that the stability constants of the corresponding complexes EuL _n ³⁺ and AmL _n ³⁺, where n = 2,3 and L is DBDMDDOEMA, in water saturated nitrobenzene are comparable.     

Uptake behavior of americium on alginic acid and alginate polymer gels

The uptake behavior of Am³⁺ was investigated by using alginic acid and alginate polymer gels. The affinity of radioactive nuclides for carboxyl groups in gel matrices increased in the order of Na⁺ < Cs⁺ < Co²⁺ < Pd²⁺, Sr²⁺, Fe³⁺ < Eu³⁺, Am³⁺. Among alginate gels, calcium alginate exhibited relatively higher uptake rate and distribution coefficient of Am³⁺. The column packed with calcium alginate beads was effective for the removal of trace amounts of Am³⁺ from acidic nitrate solutions.     

Extraction of actinides and fission products from salt solutions using polyethylene glycols (PEGs)

The extraction behavior of several metal ions viz., Am³⁺, Eu³⁺, UO₂ ²⁺, Th⁴⁺, Sr²⁺ and Cs⁺ was investigated from sulphate medium employing phosphotungstic acid (PTA) and polyethylene glycol (PEG). The influence of various parameters such as pH, PTA concentration, PEG concentration and salt concentration was studied. The order of extraction followed the trend: Am³⁺>Eu³⁺>>Th⁴⁺>UO₂ ²⁺>Sr²⁺>Cs⁺ which deviate significantly from the reported order with conventional solvents. The relatively poor extraction of UO₂ ²⁺, Sr²⁺ and Cs⁺ was ascribed to their lack of interaction with the phosphotungstate anion. The separation behaviour of Am³⁺ vis-a-vis Eu³⁺ was also investigated under different experimental conditions.     

Sorption of Am<Superscript>3+</Superscript> cations on suspended silicate: Effects of pH,ionic strength,complexing anions,humic acid and metal ions

Sorption of tracer Am³⁺ to silicate particles was studied as a function of pcH (4 to 9) and of ionic strength [0.20M to 1.50M (NaClO₄)] at 298 K. The sorption increased with increased pcH from 4 to 6 above which saturation was observed. The insensitivity of Am³⁺ sorption to increased ionic strength indicates inner-sphere complexation with the surface silicate sites. The effects of different complexing anions such as carbonate, acetate, oxalate, phosphate, citrate, EDTA and humic acid, on Am³⁺ sorption were investigated. Synergistic enhancement in Am³⁺ sorption was observed in the presence of phosphate (4≤pcH≤7) and acetate (4≤pcH≤5) ligands at 0.20M NaClO₄. The presence of the other ligands inhibited Am³⁺ sorption in the order: EDTA > citrate > oxalate > carbonate. Am³⁺ sorption in the presence of HA (25.00 mg/l) increased in the pcH range of 4.0 to 5.5, then decreased. Increased ionic strength enhanced Am³⁺ sorption in the presence of 25.00 mg/l HA for 4≤pcH≤9. The sorption increased in the presence of a mixture of HA (25.00 mg/l) and phosphate (1.00·10⁻³M) as compared to that of HA (25.00 mg/l) alone. The presence of Fe³⁺ (1.00·10⁻⁴M) enhanced Am³⁺ sorption at pcH∼4 but suppressed it from pcH of 5 to 9; 1.00·10⁻⁴M of Ca²⁺ and of UO₂²⁺ ions had no effect on the sorption profile. On leave from Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai -400 085, India.     

Tunable luminescence and energy transfer process between Tb3+ and Eu3+ in GYAG:Bi3+, Tb3+, Eu3+ phosphors

A series of Eu³⁺ ions co-doped (Gd_0.9Y_0.1)₃Al₅O₁₂:Bi³⁺, Tb³⁺ (GYAG) phosphors have been synthesized by means of solvothermal reaction method. The XRD pattern of GYAG phosphor sintered at 1500 °C confirms their garnet phase. The luminescence properties of these phosphors have been explored by analyzing their excitation and emission spectra along with their decay curves. The excitation spectra of the GYAG:Bi³⁺, Tb³⁺, Eu³⁺ phosphors consists of broad bands in the shorter wavelength region due to 4f⁸ → 4f⁷5d¹ transition of Tb³⁺ ions overlapped with 6s² → 6s¹6p¹ (¹S₀ → ³P₁) transition of Bi³⁺ ions and the charge transfer band of Eu³⁺–O^2?. The present phosphors exhibit green and red colors due to ⁵D₄ → ⁷F₅ transition of Tb³⁺ ions and ⁵D₀ → ⁷F₁ transition of Eu³⁺ ions, respectively. The emission was shifted from green to red color by co-doping with Eu³⁺ ions, which indicate that the energy transfer probability from Tb³⁺ to Eu³⁺ ions are dependent strongly on the concentration of Eu³⁺ ions.     

Extraction of europium and americium into nitrobenzene by using synergistic mixture of hydrogen dicarbollylcobaltate and tetraisopropyl methylene diphosphonate

Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^?) in the presence of tetraisopropyl methylene diphosphonate [T(iPr)MDP, L] has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, HL₂ ⁺, ML₂ ³⁺, ML₃ ³⁺ and ML₄ ³⁺ (M³⁺ = Eu³⁺, Am³⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that the stability constants of the corresponding complexes EuL _n ³⁺ and AmL _n ³⁺, where n = 2, 3, 4 and L is T(iPr)MDP, in water-saturated nitrobenzene are comparable.