Kinetic Studies of the Solvent Extraction of Metal Complexes. II. The Rate of the Extraction of Iron(III) with Thenoyltrifluoroacetone into Carbon Tetrachloride

Abstract

The rate of the solvent extraction of iron(III) in 4.0 M perchlorate ionic media with 2-thenoyltrifluoroacetone (TTA) into carbon tetrachloride has been measured under various conditions. The rate was found to be first order with respect to the concentration of iron(III) in the aqueous phase, first-order with respect to TTA in the organic phase, but independent and inversely first-order with respect to the hydrogen-ion concentration. From these results, it was concluded that the rate-determining step in this extraction is the formation of the first complex between the undissociated form, TTA(HA), and Fe3+ in the higher acid concentration range, but that the reaction between the anionic form, TTA(A−), and Fe3+ also becomes a rate-determining step as the acid concentration decreases. It was also found that chloride ions accelerate the extraction; this was interpreted by more rapid reactions between TTA (in the both forms, HA and A−) and an iron(III) chloride complex. From these results, the rate constants for the rate-determining reactions were calculated to be KHA=100.57 M−1 min−1 and KA=106.84 M−1 min−1 in 4.0 M(H, Na)ClO4 at 25 °C by means of these equations: −d[Fe3+]⁄dt=KHA[Fe3+][HA] (where [HA] is the total concentration of both enol and keto forms of uncharged TTA in the aqueous phase) and −d[Fe3+]⁄dt=KA[Fe3+]·[A−]. The FeCl2+ species reacts with both HA and A− more rapidly than does the Fe3+ species, and the rate constants of the reactions of the former are in both cases higher than those of the latter by a factor of 28.

Influence of Salting-Out Effects, Temperature and the Chemical Structure of the Extractant on the Rate of Copper(ii) Extraction From Chloride Media With Dialkyl Pyridine Dicarboxylates

“…[20] is theoretically less rigorous than Eq. [19], but practically it was found that the theoretical curves derived from these two equations are very close within the field of experimental conditions investigated in the present work.…”

“…The ionic strength was chosen as an experimental parameter in the present kinetic study because of the known sensitivity of the investigated system to salting-out effects, but also because various authors have shown that the addition of electrolytes such as NaCI, LiCI, NaCI0 4 , NaN0 3 , ctc., to a given extraction system, may significantly influence the rate of mass transfer (18)(19)(20)(21)(22)(23)(24)(25)(26)(27). It is of interest that there is no general tendency.…”

Synergistic extraction of iron(III) at higher concentrations in D2EHPA-TBP mixed solvent systems

“…Sekine et al [34] studied the rate of iron(III) extraction with 2-thenoyl-trifluoroacetone (TTA) in carbon tetrachloride under various conditions. They found that in the presence of chloride ion, the extraction rate was accelerated due to the formation of FeCl 2+ species which react more rapidly with TTA than do the Fe 3+ species, and the reactions in the former case were higher than those of the latter by a factor of 28.…”

Extraction kinetics of tantalum by MIBK from pulp using Lewis cell

“…Although many researchers worked on tantalum extraction using a variety of extractants, information regarding the kinetics of tantalum extraction has rarely been reported. In previous work on metal ion extraction kinetics Biswas, 1979, 1980;Sekine et al, 1973), the rate constants and reaction orders were evaluated by the pseudo rate-constant (q) method which is based on the concentration change in the aqueous phase. In contrast, the recent work on metal ion extraction kinetics have used the flux (F) method by the single drop, RDC, and Lewis cell techniques (Biswas and Mondal, 2003a;Biswas et al, 2005;Javanshir et al, 2011).…”