Cyanex 302: An extractant for Fe from Chloride Medium

The solvent extraction of Fe from aqueous chloride solution by bis-(2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex 302, H2A2) dissolved in kerosene has been investigated over a wide range of aqueous acidity as a function of phase contact time, concentrations of Fe, H and Cl in the aqueous phase, Cyanex 302 concentration in the organic phase and temperature. The equilibration time is 50 min. The distribution ratio is found to be independent on [Fe] in the aqueous phase at a constant aqueous acidity and extractant concentration. The H, extractant and Cl dependences are -1, 0.5 in low concentration region of extractant and -0.5, respectively; which suggest that extraction occurs via the following two parallel reactions: (i) FeCl3 + 0.5 H2A2(o) FeCl2.A(o) + H + + Cl; and (ii) FeCl2 + + 0.5 H2A2(o) -----FeCl2A(o) + H . Temperature dependence data give ∆H value of 9.95 kJ/ mol. The loading capacity of Cyanex 302 towards Fe is 29.41 g Fe/100 g Cyanex 302. The extraction equilibrium constant (Kex) is 10. Extraction ratio is found to be dependent on diluent used. Stripping of the extracted complex is found to be a difficult task, but may be made effective by a solution containing 6 M H2SO4 and 1 M Na2C2O4.