PNP-16-crown-6 derivatives as ion carriers for Zn(II), Cd(II) and Pb(II) transport across polymer inclusion membranes

Transport rate of metal cations can be explained by the size of substituents, namely larger substituents such as 7 and 8 prefer Pb(II) cations. The bis-PNP-lariat ethers remove Zn(II), Cd(II) and Pb(II) more efficiently than simple PNP-lariat ethers. The increase of linker length in the bis-PNP-lariat ether molecules lowers the metal cations’ transport rate. In addition, the synergetic effect for lead(II) transport across polymer inclusion membrane (PIM) with PNP-lariat ether 9 and DNNS was using PNP-lariat ethers—carriers 1 and 2 in a PIM system, Zn(II) and Cd(II) were transported with low selectivity from acidic aqueous source phase solutions. The ether 3 used to transport Zn(II) and Cd(II) cations from aqueous phase at pH 5.0 into hydrochloric aqueous solution shows high selectivity of Cd/Zn, but small efficiency of process.