Extraction of Co(II) and Ni(II) as chelates of 3,5-bis((E)-(2-hydroxybenzylidene)amino)benzoic acid

Abstract

 3,5-bis((E)-(2-hydroxybenzylidene)amino)benzoic acid (H2BAB) was synthesized via the condensation of two moles of 2-hydroxybenzaldehyde and one mole of 3,5-diaminobenzoic acid in methanol. The Co (II) and Ni(II) complexes were crystallized as neutral square planar chelates from an equimolar reaction mixture of the ligand and metal ions. H2BAB and its Co(II) and Ni(II) complexes were characterized based on IR,  C-NMR and UV spectroscopy. The complexes were further analysed via conductivity and stoichiometry determinations. The results indicate that the ligand ligated to the metals through the two azomethine N atom and the two hydroxy O atom in an ONON fashion leading to deprotonation of the phenolic groups. Solvent extraction of the complexes NiBAB and CoBAB were carried out using CHCl3 as organic solvent in 5% dimethylformamide. .Co(II) was quantitatively extracted between pH 5-7, while Ni(II) was quantitatively extracted at pH 6-8. Nickel(II) was successfully separated from cobalt(II) from 10-3 mol dm-3 HNO3 using 5% H2BAB/DMF, 0.05 mol dm-3 CN- as masking agent and CHCl3 as organic solvent in four-cycle extraction.  Key Words: Solvent Extraction, Complex Formation, Characterization, Spectroscopy.