Fundamentals of the Use of Mixed Solvents in Solvent Extraction of Metal Ions

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The solvent extraction systems, which consist of copper (II), benzoic acid and 1-octanol-benzene or 2-octanone-benzene mixed solvents, were selected for the purpose of studying the effects of mixed solvents on the solvent extraction of metals. In the analysis of the extraction equilibrium on the extraction of metal ion with an extracting reagent, it is indispensable to have information about the partition of the extracting agent. The partition and dimerization constants ofbenzoic acid have been determined in the 1-octanol-benzene and 2-octanone-benzene mixed solvent systems. The increase in the partition constant of monomeric benzoic acid and the decrease in the decrease in the dimerization constant of the acid in the organic phase were quantitatively explained taking into account solvation of monomeric benzoic acid by one 1-octanol or 2-octanone molecules. But, in a higher 1-octanol region of 1-octanol-benzene mixed solvents, the partition and dimerization constants were found to beco … More me smaller than those predicted by solvation of the monomeric acid by one 1-octanol molecule. This is attributable to hydration of the monomeric benzoic acid because of increasing the concentration of water with increasing content of 1-octanol in the mixed solventsBy using the same 1-octanol-benzene and 2-octanone -benzene mixed solvents with a wide variety of mixing ratio as those used for the analysis of the partition equilibrium of benzoic acid, the extraction of copper (II) with benzoic acid was carried out. The monomeric and dimeric copper (II) benzoates were found to be responsible for the every extraction systems. In the present mixed solvent systems, the following relation between the partition constants of CuA_2 (main monomeric extracted species) and HA (monomeric benzoic acid) was found to be hold : KD,CuA_2=CKD,HA^2, which C is the certain constant corresponded to the each similar series of solvents. In addition, it has been proved that the present mixed solvents with a certain composition are superior to chloroform in the extraction of copper (II) with benzoic acid. Less