The temperature effect on the solvent extraction of copper(II), cobalt(II) and nickel(II) by Schiff base salicylideneaniline (SAN) in chloroform from sulfate aqueous medium of constant ionic strength was studied. The temperature dependence of the extraction equilibrium constants were investigated to estimate the variation of enthalpy (ÁH) and entropy (ÁS). These thermodynamic functions were, as a result, calculated and discussed in conjunction with the structure of the extracted species. It was found that the extraction of each metal increased with increase in temperature. Besides ÁH and ÁS have been discussed in connection with the nature of bonding and also the symmetry of the metal complexes. It was established through this study that the types of bonding in the complexes formed in the aqueous solution are clearly reflected by the values of ÁH and ÁS for the complex formation reaction.
IntroductionSchiff base SAN is an efficient extractant for transition divalent metal from sulfate media. In our previous work [1] Cu(II), Co(II) and Ni(II) have been extracted by means of SAN in three different diluents and investigated in detail. The stoichiometry of the extraction of these species was determined by the slope analysis method. The extraction reaction proceeded by cation exchange mechanism and the extraction species were CuL 2 HL, CoL 2 HL and NiL 2 . by extending this investigation, the effect of temperature up on the extraction have been introduced and the mechanism of the extraction process were carried out and discussed in the light of the results obtained.The effect of temperature on the extraction of Cu(II), Co(II) and Ni(II) has been studied by several authors. The temperature effect on the extraction of transition divalent metals such as Cu(II), Co(II) and Ni(II) reported was investigated by means of the extraction of these metals with mixture of HTTA and TBP and TOPO [2][3][4][5][6]. Data of the temperature influence on extraction of Cu(II), Co(II), Ni(II) with neutral organophosphorus extractants were already published [7]. Schiff base complexes were chosen in order to capitalise on the reversible nature of imine bond formation Schiff bases complex
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