Selective Extraction of Iron(III) from Aqueous Nitrate Solution in the Presence of Cobalt(II), Copper(II) and Nickel(II) Ions Using Bis(Δ²-2-imidazolinyl)-5,5′-dioxime

Abstract

The feasibility of using bis(Δ²-2-imidazolinyl)-5,5′-dioxime (H₂L) for the selective extraction of iron(III) from aqueous solutions was investigated by employing an solvent-extraction technique. The extraction of iron(III) from an aqueous nitrate solution in the presence of metal ions, such as cobalt(II), copper(II) and nickel(II), was carried out using H₂L in binary and multicomponent mixtures. Iron(III) extraction has been studied as a function of the pH, equilibrium time and extractant concentration. From the extracted complex species in the organic phase, iron(III) was stripped with 2 M HNO₃, and later determined using atomic-absorption spectrometry. The extraction was found to significantly depend on the aqueous solution pH. The extraction of iron(III) with H₂L increases with the pH value, reaching a maximum in the zone of pH 2.0, remaining constant between 2 and 3.5 and subsequently decreasing. The quantitative extraction of iron(III) with 5 × 10^-3 M H₂L in toluene is observed at pH 2.0. H₂L was found to react with iron(III) to form ligand complex having a composition of 1:2 (Fe:H₂L).