Separation and Recovery of Fe(III) and Cr(III) from a Tannery Filtrate using Cyanex 272

Cyanex 272, diluted in the aliphatic solvent Escaid 110, has been investigated as an extractant for Fe(III) from a sulfate medium. Speciation studies have revealed the presence of Fe(SO4)2- and FeSO+4 as the major aqueous-phase ferric complexes with the ratio of their contributions being proportional to the concentration of SO2- 4in the aqueous phase. Cyanex 272 behaved like a cation exchanger, and a complex FeR3(HR) was formed in the organic phase. Results indicated that this extraction of Fe(III) was reasonably selective over Cr(III) and Zn(II). Complete stripping of the extracted Fe(III) could be achieved by 0.50 mol L^-1 H2SO4. Although at room temperature the kinetics of both the extraction and the stripping processes were slow, they considerably improved at higher temperature. The selectivity of Cyanex 272 has led to the development of a process for the separation and recovery of Fe(III) and Cr (III) from a tannery filtrate. The solvent maintained its capacity after repeated extraction and stripping cycles.