Selective recoveries of Fe(III) and Cr(III) from a tannery filtrate using Cyanex 923

The separation of Fe(III) and Cr(III) has been proposed by liquid–liquid extraction with 0.50 M Cyanex 923. Fe(III) was selectively extracted from the mixed H2SO4 and NaCl medium leaving pure Cr(III) in the raffinate. The developed method has been used to separate and recover Fe(III) and Cr(III) from a tannery filtrate. The modeling experiments, simulating the concentration of Fe(III) and H2SO4 in the original tannery filtrate, have suggested the presence of the metal ion predominantly in the form of FeHSO42+. The addition of Cl− ions in the aqueous phase resulted into the development of FeCl3, which was extractable in Cyanex 923 by solvation with two extractant molecules. The kinetics of the extraction was reasonably fast. The stripping of Fe(III) has been carried out by 0.25 M H2SO4. The extractant solution maintained its capacity even after repeated extraction and stripping cycles.