Search Results

You are looking at 1 - 10 of 15 items for

  • Author or Editor: M. Jimenez-Reyes x
  • All content x
Clear All Modify Search

Abstract  

Complex formation of humic acids (HA)n with La3+ and Eu3+ was studied. Commercial (HA)n was purified and characterized. The stability constants were determined at several pH values and 0.2 M NaClO4 ionic strength by the Shubert’s method of radiochemical ionic exchange. The slopes of the lines
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\log ((\lambda_{0} /\lambda ) - 1) = \log \beta_{\text{M,j(HA)n}}^{\exp } + {\text{j}} * \log \left[ { ( {\text{HA)}}_{\text{n}} } \right]$$ \end{document}
were dependent on the [(HA)n]. The values of log
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\beta_{\text{M,j(HA)n}}^{\exp }$$ \end{document}
for j = 1 were the following: 6.29 ± 0.04 (pH 4.9 ± 0.4) and 7.61 ± 0.03 (pH 5.9 ± 0.1) for lanthanum and 7.31 ± 0.01 (pH 5.9 ± 0.2) for europium. Log
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\beta_{\text{M,j(HA)n}}^{\exp }$$ \end{document}
was determined as well for higher values of the j parameter and these values were: 12.2 ± 0.1 (j = 2, pH 7.7 ± 0.2), 15.6 ± 0.2 (j = 3, pH 4.9 ± 0.4) and 16.05 ± 0.07 (j = 3, pH 5.9 ± 0.1), for lanthanum and 13.18 ± 0.03 (j = 2, pH 5.9 ± 0.1) for europium. A discussion is presented about the complex formation regarding pH and [(HA)n].
Restricted access

Abstract  

The35S products formed in irradiated CCl4, CHCl3 and C2HCl3 were analysed. In CCl4 no trace of C35SCl2 was found whereas35SO2 was identified. In CHCl3, CCl3 35SCl was an important product and after saturation with oxygen CCl3 35SO2Cl became a major product. In C2HCl3,35S product appeared as compound of low volatility.

Restricted access

Abstract  

A study of the isotope exchange reaction U(III)org/U(IV)aq in the extraction system: 7M HCl — tributyl phosphate (TBP) — toluene has been performed. For 20 s of contact the results show a separation factor235U/238U of 1.014. This large separation factor is explained by the oxidation reaction of235U(III) and238U(III).

Restricted access

Abstract  

The chemical behavior of calcium, barium and radium in the ion exchange resins Dowex 50W-X8, AG 50W-X8 and Merk I in the presence of ammonium tartrate, EDTA, and citrate has been studied. No differences were observed in results while using any one of the three resins. Calcium, barium and radium were fixed to the exchange column at pH 4.8 EDTA solution. Calcium was eluted in an EDTA solution at pH 5.3, barium and radium between pH 8–11. Elution in citrate media for calcium was achieved at pH 6.1 and for radium at pH 10. In ammonium tartrate, calcium was eluted at pH 6, barium and radium at pH 11.5. Radium was also eluted from the ion exchange resins with a 2M nitric acid solution. The radium free of calcium was electrodeposited onto a stainless steel disc cathode using a 0.1 M potassium fluoride solution, pH 12–14, with a yield of >50%. The energies of226Ra were analyzed through high resolution -spectra. The226Ra utilized for these experiments was separated from Mexican carnotite.

Restricted access

Abstract  

The behavior of uranyl ion and tervalent Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu in the solvent extraction system: M–HCl–H2O–TBP has been studied together with chromatographic elution of the first nine of these rare earth elements using DOWEX 50Wx8 resin. >99.5% of the rare earth elements, with a single exception, remained in the aqueous phase of the solvent extraction system where the initial concentration of hydrochloric acid was between 4 and 6 M. Under these conditions uranyl ions were readily extracted by TBP. The rare earth elements were quantitatively eluted from the chromatographic column using 6M hydrochloric acid solution and the uranyl ions in a 0.75M sulfuric acid solution.

Restricted access

Abstract  

Obsidian samples from 13 Mexican quarries (Sierra de Pachuca and Zacualtipan, Hidalgo, Zaragoza and Oyameles, Puebla, Altotonga Veracruz and eight sites of the Zinaparo — Varal — Churintzio Hills region) have been analyzed by NAA. The concentration of 19 elements, major and trace, are reported. Excepting Altotonga Veracruz, the chemical composition of other obsidian flows was found homogenous. The region of the Varal obsidian was delimited. An excellent correlation between ytterbium and lutetium contents in obsidians was found.

Restricted access

Abstract  

This study reports sodium and chlorine values in g/g, as detemined by neutron activation analysis in washed hair and nails from healthy and cystic fibrosis children. The values thus determined in cystic fibrosis tended to be higher than those in controls, however statistical differences were not significant (p>0.01). Additional experiments were carried out for comparison between washed and unwashed samples of the cystic fibrosis and control group and only the differences between washed and unwashed cystic fibrosis nails were significant (p<0.01) in both odium and chlorine values. Analysis of a standard reference milk sample, A-11 from IAEA, for the elements mentioned above gave a good agreement with the certified values.

Restricted access

Abstract  

We report results obtained on the separation of lanthanum, cerium, and samarium from synthetic and natural uranium samples by means of solvent extraction and ion exchange. Quantitative determinations of these elements were performed using X-ray fluorescence, polarography, and chemical or neutron activation analysis.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors: H. López-González, M. Jiménez-Reyes, M. Solache-Ríos, and A. Rojas-Hernández

Abstract  

Solubility product (Lu(OH)3(s)⇆Lu3++3OH) and first hydrolysis (Lu3++H2O⇆Lu(OH)2++H+) constants were determined for an initial lutetium concentration range from 3.72·10−5 mol·dm−3 to 2.09·10−3 mol·dm−3. Measurements were made in 2 mol·dm−3 NaClO4 ionic strength, under CO2-free conditions and temperature was controlled at 303 K. Solubility diagrams (pLuaq vs. pC H) were determined by means of a radiochemical method using 177Lu. The pC H for the beginning of precipitation and solubility product constant were determined from these diagrams and both the first hydrolysis and solubility product constants were calculated by fitting the diagrams to the solubility equation. The pC H values of precipitation increases inversely to [Lu3+]initial and the values for the first hydrolysis and solubility product constants were log10 β* Lu,H = −7.92±0.07 and log10 K*sp,Lu(OH)3 = −23.37±0.14. Individual solubility values for pC H range between the beginning of precipitation and 8.5 were S Lu3+ = 3.5·10−7 mol·dm−3, S Lu(OH)2+ = 6.2·10−7 mol·dm−3, and then total solubility was 9.7·10−7 mol·dm−3.

Restricted access

Abstract  

Obsidian samples from San Miguel Ixtapan Mexico State, Mexico were analyzed by means of neutron activation. Statistical treatments such as bivariate, cluster and principal-components analyses were applied to the data set. Obsidians were identified as coming from three important sources: Sierra of Pachuca in the state of Hidalgo, Zinapécuaro and Zináparo-Varal in the state of Michoacán.

Restricted access