Solvent Effects on the Extraction of Copper(II) with Lauric Acid

Solvent extraction system is one of the effective techniques used for separation of metal cations from aqueous solutions [1-8]. It is a suitable method for preventing and protecting environment from pollution. The extraction of copper(II) using carboxylic acids has been a subject of much work research [9-13]. Lauric acid was employed as an extractant for the separation of numerous cations, the composition of extracted species and their extraction constants were reported [14-16]. Ghanadzadeh et al. [17] established that lauric acid extracts capably copper(II) from aqueous solutions and it was shown that in the organic phase dimeric complexes of the (CuR2.HR)2 formula are formed. The solvents have a great importance on the extraction efficiency and distribution ratio due to their polarity [18]. As a consequence, studies of the effect of solvents on the extraction of metal ions have been reported by many researchers [19-23]. Yamada et al. [24] studied the extraction of gallium (III) with decanoic acid in different solvents. They established that the extracted decanoates were more extensively polymerized in the less polar solvent than the more polar solvent. However, Ghebghoub et al. [25] investigated the effect of diluents on the extraction of copper(II) with di(2-ethylhexyl)phosphoric acid. They found that in the extracted species were CuL2 and (CuL2.2HL) in polar and nonpolar diluents respectively. The present paper describes the results obtained from the solvent extraction of copper(II) from nitrate medium by lauric acid in several organic solvents. The scope of the work is to determine the stoichiometries coefficients of the extracted species and their equilibrium constants. In addition, the solvent effects on this extraction system are examined and the interaction with several solvents is interpreted.