Solvent extraction of zinc by 2-hexylpyridine in benzene from aqueous mineral acid — Thiocyanate media |
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Authors: | M S Bhatti Shamasud-Zuha |
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Institution: | (1) Nuclear Chemistry Division, Pakistan Institute of Nuclear Science and Technology, P.O. Nilore, Rawalpindi, (Pakistan) |
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Abstract: | Solvent extraction of Zn(II) by 2-hexylpyridine (HPy) in benzene has been studied from aqueous mineral acid—thiocyanate media.
The extraction, though dependent on the acidity of the aqueous phase, is poor from mineral acids (HCl, HNO3 or H2SO4). Addition of 0.02M KSCN to the aqueous phase enhances the distribution ratio by a factor of almost one thousand. The stoichiometry
of the extracted complex established by the usual slope analysis method indicates that an ionic type complex, e.g. Zn(SCN)4·(HPyH)2, is responsible for extraction. Complexing anions like acetate, oxalate or citrate at 1 M concentration mask the extraction
of Zn(II) almost completely. Separation factors determined at optimal conditions (0.1M HPy in benzene −0.05M H2SO4+0.2M SCN−) indicate that Zn(II), along with Hg(II), can be separated in a single extraction from a number of metals, e.g. Cs(I), Sr(II),
Ln(III), Y(III), Cr(III) and (VI). Other metals of interest like Cu(II), Co(II), Fe(III), Mo(VI), U(VI) and Tc(VII) are coextracted
but the separation factors are large enough to allow separation in a multistage extraction process. |
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