Etude de la sélectivité d’extraction du cobalt (II) et du nickel(II) par l’acide caprique.

Abstract

In this research, we focused on extraction selectivity of nickel (II) and cobalt (II) by capric acid (decanoic) as a function of pH, extractant concentration, nature of the diluents and temperature. The stoichiometry of the extracted organometallic complexes of each metal was determined by the bilogarithmic slope graph method. The organometallic complexes extracted in the organic phase are of the type: NiR2(HR)2 and CoR2(HR)2 of monomeric structure and octahedral geometry. The extraction of nickel(II) and cobalt(II) was performed in chloroform, toluene and cyclohexane. The values of the extraction’s constants in the different solvents were decreased and follow the following decreasing order: Cyclohexane > toluene > chloroform for nickel(II) Cyclohexane > chloroform > toluene for cobalt(II) The study of the effect of temperature on the liquid-liquid extraction of nickel (II) and cobalt (II) in chloroform, our work demonstrates that the extraction rate of these two metals increases with temperature. Thermodynamic parameters such as enthalpies, entropies and free energies of extraction of each metal were determined. Ni (II) and Co (II) extraction by capric acid in chloroform revealed a coextraction of these metals. The formation of a mixed complex was confirmed by the slope analytical method and by visible and IR spectroscopy.