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1 Ars Separatoria Acta

1 2007

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Selective removal of Cu(II), Co(II), Zn(II), and Ni(II) with ionizable dibenzo-16-crown-5 and dibenzo-19-crown-6 lariat ethers as ion carriers in polymer inclusion membrane transport

Kozłowski C. A., Walkowiak W.

Ars Separatoria Acta

2007

No. 5

19-26

A selective removal of transition metal cations, i.e. Cu(II), Co(II), Zn(II), and Ni(II), with ionizable dibenzo-16-crown-5 and dibenzo-19-crown-6 lariat ethers as ionic carriers in transport across polymer inclusion membrane has been presented. The competitive transport from aqueous nitrate solutions containing metal ions at concentrations of 0.0010 M at pH 4.0 and 7.0 through the cellulose triacetate membrane with 0.5 M lariat ether 1 and 2 (based on a plasticizer) as the ion carrier and o-nitrophenyl pentyl ether (ONPPE) as the plasticizer into 0.5 M hydrochloric solution was performed. For pH = 4.0 and 7.0 of source aqueous phases the selectivity orders were as follows: Cu(II) > Co(II) > Zn(II) > Ni(II), and Cu(II) > Zn(II), Ni(II), Co(II), respectively. The semi-empirical equation was used for calculations of enthalpy formation for complexes of lariat ethers studied with transition metal cations. The two possibilities of metal cation-lariat ether coordination were assumed, i.e. via the crown ether cavity or ionizable carboxylic group. We found that for the both lariat ethers studied at pH 4.0 of source phase the transport rate linearly decreases with the enthalpy of formation increase. This correlation confirms that the observed behavior is connected with the stability of complexes formed by interaction of the lariat ether ring and the transition metal cations studied.