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

Masahiro TAKAHASHI*, Yasuhiro YAMASHITA† and Satoru KOSAKA††

Department of Chemistry and Biochemistry, Suzuka National College of Technology;
Shiroko-cho, Suzuka-shi 510-0294 Japan
† Toyohashi University of Technology; 1-1 Hibarigaoka, Tenpaku-cho, Toyohasi-shi
441-8122 Japan
†† Toyota Central Research and Development Laboratories, Inc.; 41-1 Nagakute Yokomichi,
Nagakute-cho, Aichi-gun, Aichi 480-1131 Japan

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.
Mn++n•ª”n + 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, 2.2×10-6 kg-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.


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