Kinetics of stripping of Fe 3+–D2EHP complexes from D2EHPA–kerosene phase by aqueous HCl–Cl − phase using the single drop technique

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The title system has been investigated from the kinetic viewpoint. The kinetics are found to be dependent on the method of preparing the Fe 3+–D2EHP complex. The species extracted at [HCl] of 0.03 and 1.2 M have been used in single drop experiments. Moreover, the species extracted at a particular [HCl] have been used for stripping at identical [HCl]. For the stripping of the species extracted at 0.03 M HCl, the rate is proportional to [ Fe 3+– D2 EHP] and to 1/[D2EHPA] in organic phase and to [H +] in aqueous phase. The rate is independent of Cl − concentration. On the other hand, for stripping of the species extracted at 1.2 M HCl, the rate is proportional to [ Fe 3+– D2 EHP] and to 1/ [ D2 EHPA] in organic phase, to [H +] in its higher concentration region, to 1/ [ H +] in its lower concentration region and to 1/ [ Cl −] in aqueous phase. The experimental points for the above two categories and also those for extracting and stripping at identical [HCl] are best fitted by: J b ( kmol/m 2 s)=[ Fe] (T), (o) 1/2[ H 2 A 2] (0) −1[ H +] ( a) (140×10 −9 x 0 +17×10 −9 x 1 +12×10 −9 x 2 )+3.8×10 −9[ Fe] ( T), ( o) 1/2[ H 2 A 2] ( o) −1/2[ HCl] ( a) −1 x 3 where x 0, x 1, x 2, and x 3 are the fractions of Fe 3+, FeCl 2+, FeCl 2 + and FeCl 3 species existing at a particular [HCl], respectively. From the temperature-dependence data, the values of E a, Δ H ± and Δ S ± have been evaluated and found to be functions of [HCl]. The mechanisms of extraction, particularly of the rate-determining steps, have been suggested. The stripping rate data in combination with the forward extraction rate data have been compared to the equilibrium data and found to agree well.