Moncef Stambouli

Solvent extraction of titanium by tributylphosphate, trioctylphosphine oxide and decanol from chloride media

Abstract Solvent extraction of titanium from both hydrochloric acid and calcium chloride solutions has been investigated. Polarographic analysis showed that the dissolved titanium is present as Ti(IV) in chloride solutions. Two extractants, tributylphosphate (TBP) and decanol, were used separately and mixed. The effects of the reaction time, the concentration of HCl and CaCl 2 in the aqueous phase, and the extractant concentration in the organic phase were studied. It is shown that the kinetics of the extraction process are very fast, since equilibrium is reached after 3 min. In addition, the extraction of Ti(IV) increases with the total chloride concentration in the aqueous phase, as well as with the extractant concentration in the organic phase. Extraction of about 95% of titanium by 1 mol/1 TBP from hydrochloric acid media was possible, as well as the extraction of 99% of titanium by 0.5 mol/l TOPO from a 6 mol/l solution of total chloride.

Metal complexes stability constant determination by hyphenation of capillary electrophoresis with inductively coupled plasma mass spectrometry: the case of 1:1 metal-to-ligand stoichiometry.

Nuclear energy development has raised new issues like radionuclides biogeochemistry. The modelling of their biochemical properties involves the accurate determination of thermodynamical data, like stability constants. This can be achieved by using hyphenated capillary electrophoresis (CE)-ICPMS and the method was applied successfully on 1:1 lanthanum-oxalate and uranyl-oxalate complexes. Several significant steps are discussed: choice of analytical conditions, electrophoretic mobility calculation, mathematical treatment of experimental data by using linear regressions, ligand concentration and ionic strength corrections. The following values were obtained with a good precision for lanthanum-oxalate and uranyl-oxalate complexes: log(K degrees (LaOxa(+)))=6.10+/-0.10 and log(K degrees (UO(2)Oxa))=6.40+/-0.30, respectively, at infinite dilution. These values are consistent with the literature data, showing CE-ICPMS potential for metal complexes stability constants determination.

Thermodynamic and kinetic studies of palladium (II) extraction by extractant mixtures containing LIX 63: Part I. Thermodynamic study

Abstract Extraction of palladium (II) by LIX 63, TOPO, TIBPS, Aliquat 336 and HDEHP individually or in mixture with LIX 63, was studied in HCl (1 mol l−1). It was found that the association of LIX 63 with TOPO or Aliquat 336 enhances the extraction rate of Pd(II). Aliquat 336 is the most powerful additive, the extraction thermodynamics were carefully investigated for this case. The comparison of the distribution curves, for individual extractants and their mixtures, indicated a significant synergism that was explained by the formation of a mixed species of Pd(II), LIX 63 (H2Ox) and Aliquat 336 (Ali): [PdCl 3 (H 2 Ox)](Ali) , in addition to those formed with the individual extractants: [PdCl 4 ](Ali) 2 and [PdCl 2 (H 2 Ox) 2 ] ; the formation constants of these three compounds were determined.

SOLVENT EXTRACTION OF NICKEL(II) BY MIXTURE OF 2-ETHYLHEXANAL OXIME AND BIS(2-ETHYLHEXYL) PHOSPHORIC ACID

The extraction of nickel(II) from acidic aqueous solutions using a mixture of 2-ethylhexanal oxime (EHO) and bis(2-ethylhexyl) phosphoric acid (D2EHPA) in dodecane has been investigated as a function of total concentrations of each extractant, metal and protons. The aqueous salt concentration is proved to have no significant effect for both ammonium nitrate and chloride. The extracted organic complex is then Ni(Ox)2(HOx)2(HA)2 or Ni(HOx)4A2, where HA denotes the organo-phosphoric acid and HOx the oxime. A complementary isomolecular study has been achieved to confirm this stoichiometry. As aggregation plays a crucial role in extraction phenomenon, Vapor Pressure Osmometry (VPO) measurements have been carried out in order to determine the aggregation numbers for either the separate extractants or their mixtures. The bis(2-ethylhexyl) phosphoric acid is mainly under dimer and trimer forms, while no mixed aggregation is observed.

Search for evidence of life in space: analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry.

Within the context of the future space missions to Mars (MSL 2011 and Exomars 2016), which aim at searching for traces of life at the surface, the detection and quantitation of enantiomeric organic molecules is of major importance. In this work, we have developed and optimized a method to derivatize and analyze chiral organic molecules suitable for space experiments, using N,N-dimethylformamide dimethylacetal (DMF-DMA) as the derivatization agent. The temperature, duration of the derivatization reaction, and chromatographic separation parameters have been optimized to meet instrument design constraints imposed upon space experiment devices. This work demonstrates that, in addition to its intrinsic qualities, such as production of light-weight derivatives and a great resistance to drastic operating conditions, DMF-DMA facilitates simple and fast derivatization of organic compounds (three minutes at 140 degrees C in a single-step) that is suitable for an in situ analysis in space. By using DMF-DMA as the derivatization agent, we have successfully identified 19 of the 20 proteinic amino acids and been able to enantiomerically separate ten of the potential 19 (glycine being non-chiral). Additionally, we have minimized the percentage of racemized amino acid compounds produced by optimizing the conditions of the derivatization reaction itself. Quantitative linearity studies and the determination of the limit of detection show that the proposed method is also suitable for the quantitative determination of both enantiomeric forms of most of the tested amino acids, as limits of detection obtained are lower than the ppb level of organic molecules already detected in Martian meteorites.

Stability constants determination of successive metal complexes by hyphenated CE-ICPMS

The study of radionuclides speciation requires accurate evaluation of stability constants, which can be achieved by CE‐ICPMS. We have previously described a method for 1:1 metal complexes stability constants determination. In this paper, we present its extension to the case of successive complexations and its application to uranyl‐oxalate and lanthanum‐oxalate systems. Several significant steps are discussed: analytical conditions choice, mathematical treatment by non‐linear regression, ligand concentration and ionic strength corrections. The following values were obtained: at infinite dilution, log(β1°(UO2Oxa))=6.93±0.05, log(β2°(UO2(Oxa)22−))=11.92±0.43 and log(β3°(UO2(Oxa)34−))=15.11±0.12; log(β1°(LaOxa+))=5.90±0.07, log(β2°(La(Oxa)2−))=9.18±0.19 and log(β3°(La(Oxa)33−))=9.81±0.33. These values are in good agreement with the literature data, even though we suggest the existence of a new lanthanum‐oxalate complex: La(Oxa)33−. This study confirms the suitability of CE‐ICPMS for complexation studies.

Scale-up of nanoemulsion produced by emulsification and solvent diffusion.

The scale-up of nanoemulsions (NEs) produced by emulsification and solvent diffusion process was successfully achieved in the present work. Up to 1500 mL of NEs were produced with olive oil, castor oil, almond oil, or Arlamol™ E by using a Y-shaped mixer device. NE droplet sizes were significantly modulated from 290 to 185 nm by changing the process parameters without modification of the formulation composition. Smaller NE droplet sizes were obtained by (1) decreasing the internal diameter of the Y-mixer from 5 to 0.8 mm, (2) increasing the flow rates of the organic and the aqueous phases upon mixing, and (3) increasing the temperature of the experiment from 5°C to 40°C. All the results of NE diameters (d(sc) ) expressed as a function of the Reynolds number (Re) and the shear rate inside the Y-mixer (\documentclass{article}\usepackage{amssymb}\begin{document}\pagestyle{empty}

Study of the multicomponent system wet process phosphoric acid-methyl isobutyl ketone at 40 ◦ C phase equilibria and extraction performances

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Paraquat detoxication with multiple emulsions

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Thiosubstituted Organophosphorus Acids as Selective Extractants for Ag(I) from Acidic Thiourea Solutions

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