Modified cyclodextrin polymers as selective ion carriers for Pb(II) separation across plasticized membranes

In the present work the hydrophobic β-cyclodextrin (β-CD) polymers have been used as macrocyclic ion carriers for separation of Pb(II), Zn(II), and Cu(II) ions from dilute aqueous solutions by transport across polymer inclusion membranes. The β-CD polymers were prepared by cross-linking of β-CD with 2-(1-docosenyl)-succinic anhydride derivatives in anhydrous N,N-dimethylformamide in the presence of NaH. The metal ions were transported from aqueous solutions containing heavy metal ions through plasticizer triacetate membranes with dimer and polymer β-CD derivatives into distilled water. The selectivity of lead(II) over other metal ions in the transport through polymer inclusion membrane was very high, especially for dimer cyclodextrin carrier. In the case of competitive transport of Pb(II), Cu(II), and Zn(II) ions through plasticized immobilized membranes the selectivity of process is controlled via formation of ion pairs of β-CD hydroxyl groups with metal cations. The polymer and dimer of β-CD linked by 2-(1-docosenyl)-derivative used as ionic carriers for competitive transport of metal ions show preferential selectivity order: Pb(II)  Cu(II) > Zn(II). Application of ion carriers mixtures (β-CD polymers and palmitic acid) causes the increase of Pb(II) maximal removal from dilute aqueous solution. The weight-average molecular weight (M_W) and the chemical structure of the β-CD polymers were determined using high-performance size exclusion chromatography with refractive index detector, and ¹H NMR spectroscopy.