Sorption of heavy metal ions by silica gel-immobilized, proton-ionizable calix[4]arenes.

Silica gel-immobilized, di-ionizable calix[4]arenes are employed as stationary phases in ion-exchange chromatography for selected heavy metal ions. Sorption efficiencies for Pb(2+) are dependent on the structure of the calix[4]arene ligand and the linker that joins the ligand to the silica gel, as well as the acidity of the sample solution. Although the resins exhibit only poor sorption of Cd(2+), they are found to be scavengers for Hg(2+). Competitive sorption studies are conducted with selected resins.