SYNERGISTIC EXTRACTION OF IRON(III) AT HIGHER CONCENTRATIONS IN D2EHPA-TBP MIXED-SOLVENT SYSTEMS

The extraction of iron(III) from chloride solutions at macrolevel conc entration by different solvents such as tri-n-butyl phosphate (TBP), d i(2-ethylhexyl) phosphoric acid (D2EHPA), and their mixture in various proportions has been investigated at different acid concentrations. T he synergistic extraction of iron(III) with a mixture of TBP and D2EHP A was studied and the results were compared with that of the extractio n by individual solvent alone. An increase in the concentration of the synergist, TBP, in the D2EHPA-TBP solvent system resulted in an incre ase in the synergistic coefficient value. The experimental data are tr eated graphically to explain the formation of organic phase extracted species, and the equilibrium extraction constants for the species are determined. It is found that a maximum of two molecules of TBP are add ucted to the extracted species of the corresponding nonsynergistic sys tem. Stripping of iron(III) with hydrochloric acid from loaded D2EHPA was found to increase with an increase in acid concentration. In the c ase of D2EHPA-TBP mixtures, stripping efficiency was increased with an increase in acid concentration up to a certain level and then it was decreased. The experimental results indicate that an iron exchange rea ction between loaded D2EHPA and TBP proceeds during stripping at a hig her concentration of hydrochloric acid (from mixed loaded solvent syst em). A plausible mechanism for iron(III) extraction and stripping has been discussed.