The influence of alkyl chain length on extraction equilibria of Ni(II) complexes with 1-alkylimidazoles in aqueous solution/organic solvent systems

Extraction process has been studied of Ni(II) complexes with 1-alkylimidazoles (with alkyl=C4H9 through C14H29) from aqueous solutions at 25degreesC, at a fixed ionic strength (0.5; KNO3). Toluene, p-xylene, dichloromethane and 2-ethyl-1-hexanol were used as diluents. Stability constants of the complexes formed in the aqueous phase, beta(n), were determined as well as the composition and partition constants, P-c, of the extracted species. It was demonstrated that stability constants of the Ni(II) complexes with the 1-alkylimidazoles as well as their partition constants increased with increasing chain length of the alkyl substituent. The larger stability constants were received for dichloromethane. The highest values of the partition constants of Ni(II) complexes were received for the system water/2-ethyl-1-hexanol. On the basis of the UV-VIS spectra it was found that during all experiments the basic structure of the coordination polyhedron of Ni(II) has been retained.