Solvent Extraction Equilibria of FeCl<SUB>3</SUB> with TBP

Abstract

Solvent extraction equilibria of FeCl 3 with TPB from chloride solutions were analyzed by considering chemical equilibria, extraction reaction, mass and charge balance equations. The activity coefficients of solutes in aqueous phase were calculated by Bromley equation while ideal behavior was assumed for species in organic phase. Extraction reaction of FeCl 3 with TBP in the experimental range of this study was determined from the dependence of the distribution coefficient of iron on the concentration of chloride ions. By applying ionic equilibria to the results of solvent extraction experiments, equilbrium constant of the extraction reaction was estimated to be 4:5 Â 10 2 . The equilibrium concentrations of solutes in both phases after extraction could be calculated with the ionic equilibria developed in this study. The predicted distribution coefficients of iron agreed well with those measured.

A Robust and Efficient Algorithm for Computing Reactive Equilibria in Single and Multiphase Systems

“…TableS3(Supporting Information) indicates that the distribution coefficient of iron (D Fe ) increased with increasing concentrations of HCl, FeCl 3 , and TBP. The predictions obtained using the present methodology are comparable to the published data1 and exhibit good agreement with the experimental data, as shown in Figure3. In our system, iron does not exist in both phases in the same form, and consequently, the definition of the distribution coefficient of iron (D Fe ) is considered as= = • • D (iron concentration in the organic phase) (iron concentration in the aqueous phase) [FeCl HCl 2TBP] [iron present in the aqueous phase in all forms]…”

“…This choice was motivated by the fact that this is a well-understood system. 1 The main intention was to model the reactive extraction system (FeCl 3 with TBP) without a constraint on the initial guesses for predicting liquid−liquid equilibria. Here, we used the reaction equilibria and thermodynamic values from Lee et al, 1 as indicated in Table S1 of the Supporting Information.…”

“…Reactive extraction is an important class of liquid–liquid extraction processes in which, in addition to extraction, several chemical reactions occur, forming ions and solute–solvent complexes. The solvent extraction of iron and the purifications of zirconium, , uranium and plutonium, and neptunium and other actinides, among other processes, are carried out through reactive extraction. In systems containing metals that are hydrolyzable, such as zirconium, plutonium, and neptunium, the efficiency of the extraction process is dependent on the ionic strength, which, in turn, is a function of the acidity and the concentrations of various metal complexes …”

Stripping of Fe(III) from the Loaded Mixture of D2EHPA and TBP with Sulfuric Acid Containing Reducing Agents

“…10 In the case of separation of ferric iron by amines or TBP, strong HCl solution is needed, while moderate acidity is enough to selectively extract ferric iron by cationic extractants. 1,5,8 Among the extractants mentioned above, extraction of Fe(III) by D2EHPA has been extensively investigated. Difficulties have been reported in the stripping of Fe(III) from the loaded D2EHPA even with concentrated acid.…”

“…Ferric iron has a strong tendency to form complexes with chloride ion which can be extracted selectively by amines 1,2 and TBP. [3][4][5] Moreover, there is some difference in the value of pH 50 (the pH at which 50% of the metal is extracted) by cationic extractants [6][7][8][9] among Co(II), Fe(III), Mn(II) and Ni(II). 10 In the case of separation of ferric iron by amines or TBP, strong HCl solution is needed, while moderate acidity is enough to selectively extract ferric iron by cationic extractants.…”