N-(diethylthiophosphoryl)-aza[18]crown-6: synthesis and ability of solvent extraction toward lead(II), zinc(II) and cadmium(II) metal cations

This work presents the synthesis of a strongly hydrophobic, functionalized monaza crown ether, i.e., lariat ether, namely N-(diethylthiophosphoryl)-aza[18]crown-6 and its application as ion extractant in solvent extraction systems. The synthesis of thiophosphorylated aza[18]crown-6 was performed with good yield. Separation systems have been successfully developed to extract Pb(II), Cd(II) and Zn(II) into organic phase, i.e., chloroform with the crown ethers: aza[18]crown-6 and N-(diethylthiophosphoryl)-aza[18] crown-6 as extractants. The selectivity order in both crown ethers was Pb(II) >> Cd(II) > Zn(II). The obtained results suggest that N-(diethylthiophosphoryl)-aza[18]crown-6 can be used for the selective removal of Pb(II) at lower pH values than aza[18]crown-6.