Authors:M. R. Yaftian, M. R. Razipour, and D. Matt
The extractive properties of 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(diphenylphosphinoylmethoxy)calixarene towards thorium(IV) and europium(III) ions are studied.
The conventional log-log analysis of the extraction data reveals that the stoichiometry of the extracted species is 1 : 1
metal ion to ligand ratio for the two metals. The effects of ligand concentration, types of diluent and concentration of the
salting-out agents are investigated and discussed. The selectivity of the ligand for thorium and europium ions versus Mn2+, Pb2+, Cd2+, Fe2+, Ni2+ and Co2+ is examined.
Authors:M. Yaftian, R. Taheri, A. Zamani, and D. Matt
Solvent extraction of tetravalent thorium and trivalent europium ions from nitrate media into dichloromethane solution of
triphenylphosphine oxide (TPPO) has been studied. The extractant was shown to be more efficient for europium than for thorium.
A conventional log-log analysis reveals that the extraction of both metal nitrates takes place via the formation of the species
with 1 : 2 metal to ligand ratio. Thermodynamic parameters i.e., ΔG°, ΔH° and ΔS° of the extraction process using 1,2-dichloroethane as diluent have been calculated based on the influence of the temperature
on extraction equilibria in the range 293-313 K. While the extraction of europium is controlled by enthalpy changes, the extraction
of thorium is an endothermic process and is driven by entropy changes. A comparison of these data with those obtained for
the extraction of europium and thorium nitrates by two other related phosphorylated ligands, tri-n-octylphosphine oxide (TOPO) and diphenyl-N,N-dimethylcarbamoylmethylphosphine oxide (DФDMCMPO), indicates that DФDMCMPO coordinates presumably as a chelating ligand.
The solubility and solubility product of europium trifluoride were measured by radiometric, potentiometric and conductometric
methods. There are significant differences in the values of both solubility and solubility product obtained by the three different
techniques. Due to reasons discussed in the text, radiometric values seem to be more acceptable than the others. The thermodynamic
functions such as ΔH0, ΔG0 and ΔS0 for the dissolution process were also measured. The positive values of ΔH0 and ΔG0 and the negative value of ΔS0 are indicative of the slight solubility of EuF3. The dependence of solubility on pH and also on the fluoride concentration has also been studied. It was confirmed that europium
forms a monofoluoride complex in aqueous solution. The stability constant of this complex was estimated.
Authors:W. Wang, Y. Yang, H. Zhao, Q. Guo, W. Lu, and Y. Lu
The extraction of europium to a W/O microemulsion with an anionic surfactant was studied. In the sodium oleate (NaOL)/pentanol/heptane/NaCl
system, the influence of aqueous-microemulsion ratio, concentration of NaOL, extraction temperature, concentration of cosurfactant,
pH and salting-out agent on the extraction yield were investigated. Europium was probably extracted into the microemulsion
phase in the form of Eu(OL)2Cl, and the extraction yield (E%) was above 99% when R = 8. The enthalpy and entropy of Eu(III) extraction were calculated to be −12.18 kJ/mol and −61.41 J/(mol K), respectively.
The back-extraction is conducted by hydrochloric acid (0.8 mol/L), which provided better back-extraction yields (95.15%).
The present work confirms the high separation ability of purified Cyanex 301 towards trivalent americium over europium in liquid-liquid extraction. Solvent 2-nitrophenyl octyl ether (NPOE) lowered the partitioning of Am3+ but remained the separation ability over europium. Solvent toluene and 3-octanone lowered the separation factor to 1000. It is feasible to separate Am3+ from Eu3+ by Cyanex 301 which was immobilized in the macro porous polymer (MPP). 3-Octanone is a suitable solvent for dissolving NH4OH-saponified Cyanex 301 and MPP is a suitable solid supported material for column operation. A five-step column experiment demonstrated the feasibility to separate Am3+ from Eu3+ in column which was packed with Cyanex 301-impregnated MPP.
Partition of radionuclides in aqueous liquid-liquid systems allows speciation of bioinorganic forms under nondenaturing conditions. From the fresh pasteurized skim bovine milk spiked with respective radionuclides and agitated with 4% w/w water solution of apple pectin, about 80% of cesium, 22% of strontium and less than 1.5% of europium is recovered with the pectin, phase at an initial milk — pectin volume ratio of 73. This recovery fraction is proportional to the abundance of radionuclides in milk serum. No protein bound fraction of strontium extractable by Aerosol OT in isooctane was obtained. More than 3-fold preconcentration of strontium and europium radionuclides in milk is achieved after 10–15 min membraneless osmosis with pectin phase.
Methods for simultaneous determination of europium and terbium based on concentration dependent distribution is described. With these methods, the distribution ratios of elements are measured in two types of substoichiometric systems. Possibility of determining these elements simultaneously is investigated experimentally by using two pairs of substoichiometric complexans/excess extracting agents, such as DTPA/HTTA and EDTA/HTTA. Relative errors and precisions for simultaneous determination of the elements are less than 5%.
Authors:J. Ramírez-García, M. Jiménez-Reyes, M. Solache-Ríos, E. Fernández-Ramírez, H. López-González, and A. Rojas-Hernández
The solubility of europium at 0.02M, 0.1M and 0.7M NaClO4 ionic strength solutions was determined by a radiometric method and pEus-pCH diagrams were obtained. Hydrolysis constants were also determined at the same ionic strengths by pH titration and the values found were log *
1 = -7.68±0.11, -8.07±0.10 and -8.20±0.11. The log Ksp values were -23.5±0.2, -22.7±0.2 and -21.9±0.2 for 0.02M, 0.1M and 0.7M NaClO4 ionic strengths, respectively, at 303 K under CO2-free conditions and the extrapolated value at zero ionic strength was log Ksp0 = -24.15. The working pCH ranges for the calculation of the hydrolysis constants were selected from the pEus-pCH diagrams in the region where precipitation of europium oxide or hydroxide was less than 20%. Europium removal from aqueous solutions with zeolites was explored.
The interaction of the clinically used 1,2-dimethyl-3-hydroxypyrid-4-one with trivalent europium Eu(III), was investigated
by using potentiometric and spectroscopic methods. The stability constants of the EuLn(3−n)+ complexes determined by spectroscopic and potentiometric measurements were found to be log β11 = 6.5±0.3 and log β12 = 12.0±0.5. However, at pH ≥ 5, hydrolysis of the Eu-L complexes starts, resulting in the formation of needle-type, yellow
crystals. The low solubility of the Eu-L complexes in the neutral pH range is disadvantageous with respect to the use of deferiprone
as chelating agent for decorporation of trivalent f-elements.
The effect of gamma irradiation on benzene solutions of benzyldibutylamine with cetyl alcohol used for the extraction of europium
and americium from nitrate solutions was investigated. The dependence of the distribution coefficient on the dose absorbed
either by the whole system or some efficient component was measured. Nitric acid present during irradiation significantly
lowers the radiation stability, while benzyldibutylamine and cetyl alcohol appear to be radiostable components. Up to tens
of kGy's—the doses expected in an extraction process from highly active solutions—the system seems to be quite stable.