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Di(2-ethylhexyl) dithiophosphoric acid (D2EHDTPA) was examined for cadmium removal from phosphoric acid solutions. High extraction performance was achieved. By means of slope and saturation methods, the stoichiometry of the complex was postulated. Both methods indicated the presence of anhydrous CdR2 as being the metallic extracted complex, HR denoting the D2EHDTPA molecule. The stripping of cadmium from the organic phase was ensured by aqueous solutions of HCl; quantitative stripping was achieved with either HCl (4 M) or an HCl-NaCl mixture. [ABSTRACT FROM AUTHOR]

This paper deals with the solvent extraction of silver from thiourea leaching Ag ore liquors as an alternative to the traditional process involving cyanide. The investigation of the extraction mechanism of silver from acidic thiourea solution had not been clearly established to date. The extraction behavior of silver using di(2-ethylhexyl)dithiophosphoric acid (D2EHDTPA) and di(2,4,4-trimethylpentyl) thiophosphinic acid (CYANEX 302) was studied. The effect of various parameters such as concentrations of metal, mineral acid, thiourea, and extractant has been investigated. The extracted complexes have been identified through a slope method analysis as AgX(HX)5 for CYANEX 302 and AgX for D2EHDTPA, where HX denotes the extractant. Moreover, complete stripping was ensured with a mixture of NH4SCN and H2SO4. In addition we showed that a first step of extraction with D2EHPA or CYANEX 272 results in the preferential separation of Fe(III) from the Ag(I) leach solution. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The extraction of nickel(II) from various aqueous solutions by 2-ethylhexanal oxime (EHO) in dodecane has been studied as a function of total concentrations of extractant, metal and salts and of the equilibrium pH. In the absence of salts, as well as in the presence of ammonium and sodium nitrates, the extracted complex is: Ni(EHO)5(H2O). In the complexing chloride medium, two different species exist, depending on acidity: for pH lower than 4, Ni(EHO)3 Cl2(H2O) and pH above 4, Ni(EHO)4Cl(H2O). 2-ethylhexanal oxime forms multimers. In dodecane The knowledge of these association degrees is very important when EHO is used as an extracting reagent. The EHO aggregation numbers have been determined by the VPO method (Vapour Pressure Osmometry) at three temperatures (24, 29 and 34°C) in a wide concentration range (0.03–0.77 mol.kg-1). EHO forms monomers, dimers and trimers. The formation constants of these aggregates have been estimated by numerical analysis. [ABSTRACT FROM AUTHOR]