Sorption and Separation of Metallic Ions by a Macromolecular Resin Impregnated with 2-Ethylhexyl Hydrogen-2-ethylhexylphosphonate

Abstract

Studies have been conducted on the sorption equilibria of Zn(II), Mn(II), Cd(II), Cu(II), Co(II) and Sm(III) from aqueous media at low acidities by a macromolecular resin impregnated with 2-ethylhexyl hydrogen-2-ethylhexylphosphonate(2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester, EHPNA, HR). Sorption equilibria of these metallic ions(Mⁿ⁺) on the macromolecular resin impregnated with EHPNA(EHPNA-impregnated sorbent) can be expressed by a simple ion exchange reaction which is different from solvent extraction with EHPNA.

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Mn++nHR⇄MRn+nH+

The equilibrium constants Kex of Zn(II), Mn(II), Cd(II), Cu(II), Co(II) and Sm(III) were found to be 6.25×10^-3, 4.0×10^-5, 4.0×10^-5, 3.1×10^-5, 2.2×10^-6kg-sor dm^-3 and 7.69×10^-3(kg-sor)² dm^-6, respectively.
The separation factors defined by the ratios of the equilibrium constant of Zn(II)/ Cu(II), Zn(II)/ Mn(II) and Sm(III)/ Co(II) were 202, 156 and 3495, respectively.
The mutual separation from the binary metal solutions of Zn(II)/ Cu(II), Zn(II)/ Mn(II) and Sm(III)/ Co(II) using the EHPNA-impregnated sorbent has also been studied in a column operation. It was found that the selective separation is attained satisfactorily by use of the sorbent.