E. Rodríguez de San Miguel

Extraction of Cu(II), Fe(III), Ga(III), Ni(II), In(III), Co(II), Zn(II) and Pb(II) with LIX® 984 dissolved in n-heptane

Abstract The solvent extraction of some metal ions with LIX ® 984 dissolved in n -heptane was studied. The extraction order observed as the pH of the aqueous solution increases is Cu(II) > Fe(III) > Ga(III) > Ni(II) > Co(II) > Zn(II) ≈ Pb(II). The experimental data obtained are explained considering hydroxyoxime association and metal complex solvation. Numerical analysis of the data with the LETAGROP-DISTR program suggested the presence of the CuR 2 , CuR 2 2HR, FeR 3 , GaR 3 , NiR 2 , InR 3 , CoR 2 HR, ZnR 2 3HR and PbR 2 HR species in the organic phase. Complex formation between the metal cations and the buffers used was considered in the calculations. The values of the equilibrium constants for the extraction reactions are reported.

Solvent extraction of Ga(III), Cd(II), Fe(III), Zn(II), Cu(II), and Pb(II) with ADOGEN 364 dissolved in kerosene from 1–4 mol dm−3 HCl media

Abstract Distribution equilibria of approximately 0.01 mol dm −3 Ga(III), Cd(II), Fe(III), Zn(II), 0.1 mmol dm −3 Cu(II) and Pb(II) from 1–4 mol dm −3 HCl media were studied using the commercial trialkylamine ADOGEN 364 (ADG) dissolved in kerosene as extractant. Self-association of this extractant in the organic phase was taken into account when analyzing the extraction reactions. Numerical analysis of the data with the LETAGROP-DISTR program allowed the evaluation of the equilibrium constants of the proposed equilibria. The dependence of the extraction constant values with ionic strength was analyzed using the specific interaction theory (SIT) treatment, from which the interaction coefficients of Ga(III), Cd(II), Fe(III), Zn(II), Cu(II), and Pb(II) with chloride anion were estimated. Data previously obtained for HCl and In(III) extraction were also analyzed in this form. Results obtained on the stoichiometry of extracted complexes are consistent with similar published work.

Adsorption of Metallic Cations on Silica Gel-Immobilized 8-Hydroxyquinoline

TLC-grade silica gel was functionalized with 8-hydroxyquinoline via a catalyzed Mannich amminomethylation reaction. The resulting solid was characterized by FT-IR and used as a sorbent for 0.05–5 mmol·L−1 Cu(II), Cd(II), Zn(II), Pb(II), and Fe(III) from aqueous solutions in the batch mode. Experiments were carried out in both single and multiple cation solutions. The influence of the aqueous media composition on the adsorption process, the possible adsorbed species, and the adsorption kinetics are discussed. Overall equilibrium constants for these processes are reported.

CVAAS determination of naturally occurring levels of mercury in sediments after on-line preconcentration with a sol-gel sorbent doped with CYANEX-301

A new on-line preconcentration method for total mercury determination in sediments by cold vapour atomic absorption spectrometry (CVAAS) was developed. The automated on-line preconcentration step was carried out using a micro-column packed with a sorbent prepared by the sol–gel technique. Tetraethoxysilane (TEOS) as the silica precursor and bis(2,4,4-trimethylpentyl)-dithiophosphinic acid (CYANEX 301) as the mercury extractant were used in the sol–gel sorbent preparation. Mercury was eluted quantitatively from the column using 2 mol L−1 HCl and mixed on-line with NaBH4 as the reducing agent. The effect of various instrumental parameters on the analytical performance was studied. The method detection limit (DL) traced back to the quantity of sample, based on three times the standard deviation of ten sample blank measurements, was 13.2 ng g−1. The calibration curves were linear from 0.1 μg L−1 to 2 μg L−1 of Hg. The measurement precision, evaluated as the relative standard deviation obtained after analyzing ten replicates, was 0.83% and 1.04% at the 1 and 0.5 μg L−1 level of Hg(II), respectively. The accuracy of the method was examined by the analysis of certified reference materials and confirmed by ICP-MS determinations. A sample throughput of 30 measurements per hour was possible.

SOLVENT EXTRACTION OF In(III) FROM CONCENTRATED HC1 MEDIA WITH ADOGEN 364

ABSTRACT The distribution equilibria of In (III) 0.1 mmol/dm3 from HCI concentrated media (2.2-4 mol/dm3) with the commercial trialkylamine ADOGEN 364 dissolved in kerosene was studied. Due to the association processes that these type of extractants present in the organic phase, a preliminary study was performed by means of a two phase potentiometric titration with the aim of determining the degree of association and the formation constants of the aggregates. The extraction of HCI is explained on the basis of the formation of ADGHCI and (ADGHCI)2 species. With the data obtained the solvent extraction process of In(III) is discussed. The presence of (ADGHCI)lnCl3, (ADGHCI)2lnCl3 and ((ADGHCI)2)2,nCl3 species in the organic phase allows to explain more satisfactory the experimental results obtained. For all the proposed equilibria the corresponding equilibrium constant is determined from the numerical analysis of the data with the use of the Letagrop-Zeta or Letagrop-Distr programs.