Both iron(II) and (III) form complexes in aqueous thiocyanate solutions 1,2 , and solvent extraction of these metal ions from the solutions is possible with different types of extractants.3 The solvent extraction of iron(III) has been studied with neutral extractants, such as ethers, ketones, alcohols and tributylphosphate, and also with cationic extractants, such as quaternary ammonium ions.3-8 However, the solvent extraction of iron(II) from thiocyanate solutions has not been studied very much. In the present work, the solvent extraction of iron(II) and (III) as anionic thiocyanate complexes with tetrabutylammonium ions into chloroform was studied and the equilibria among the chemical species were estimated by a statistical analysis of the data. The difference in the formation and extraction behaviors of the thiocyanate complexes in these oxidation states was considered by comparing the stability and extractability of the complexes in aqueous solutions.
The solvent extraction of copper(I) and copper(II) from 1 mol dm−3 Na(X, NO3), where X−is Cl−, Br−, or I−, as ion-pairs of anionic halide complexes with tetrabutylammonium ions (tba+) into chloroform was studied in the absence and presence of a reducing agent, ascorbic acid. The extraction of copper(II) with 2-thenoyltrifluoroacetone (Htta) in chloroform from these aqueous solutions was also studied. In the absence of ascorbic acid, the extraction of copper which was added as Cu2+ with tba+ was negligible from chloride and bromide solutions but tba+CuIII3− and (tba+)2CuIII42− were extracted from iodide solutions. In the presence of ascorbic acid, the extraction of tba+CuIX2− was found from all of these halide solutions. Only copper(II) was extracted with Htta from these solutions. The distribution ratio was lower when the halide concentration was higher due to formation of copper(II) complexes in the absence of ascorbic acid and it was much lower in the presence of this reducing agent due to formation of copper(I) complexes, which were stabler than the copper(II) complexes. From the extraction data with tba+ and with Htta, the formation constants of copper(I) and copper(II) halide complexes from Cu2+ in the aqueous phase as well as the extraction constants of certain complexes into the organic phase were determined. It was concluded that the dominant metal species in the aqueous phase was Cu2+ when the halide concentration was low even in the presence of the reducing agent and thus copper(I) anionic complexes were extracted into the organic phase and the molar ratio of copper(I) complex species to Cu2+ in the aqueous phase was higher at higher halide concentrations.
The effect of the picrate (pic-) ion on Eu(III) extraction with a diamide (da) from aqueous nitric acid (0.001—0.1 mol dm-3) solutions into benzene was clarified on the basis of the stoichiometry of ion-pair extractions by analyzing the distribution data of Eu(III) and picric acid (Hpic). The extraction of Eu(III) with da was extremely enhanced by adding a hydrophobic anion of pic- to the liquid-liquid system. From analyses of the distribution data of Eu(III) and Hpic, it was concluded that the effect of the hydrophobic anion was caused by the extraction of a single ion-pair of [Eu(da)2](pic)3. The nitrate ion had no relation with the cooperative effect of da and pic-, i.e., the extraction of [Eu(da)2](NO3)3, [Eu(da)2](pic)(NO3)2, and [Eu(da)2](pic)2(NO3) was practically negligible as against the [Eu(da)2](pic)3 extraction. The cooperative effect was reduced by an increase in the aqueous HNO3 concentration, which was induced by a decrease in the pic- concentration in the aqueous phase; the dissociation of Hpic into pic- ion was suppressed by an increase in the H+ concentration, and a part of molecular Hpic was extracted into the organic phase. Furthermore, the extraction of Hpic was also enhanced by an increase in the da concentration in the organic phase, which also induced a decrease in the aqueous pic- concentration. This was found to be due to the formation of a 1 : 1 complex between da and Hpic. However, the extraction of the complexes between da and HNO3 was negligible in the acid concentration range in the present study.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.