Functionalized sol-gels for selective copper(II) separation

Inorganic-organic hybrid SiO2 sol-gels anchored with amino (NH2-CH2CH2-NH-, TMSen, and -NH-CH2CH2NH- Bis-TMSen) and mercapto (HS-) ligands have been studied as new sorbents for Cu2+ separation. The TMSen-anchored gels were found to be selective for Cu2+ removal in the presence of Cd2+ and Zn2+. In comparison, mercapto-anchored gels remove both Cu2+ and Cd2+ from a mixture of Cu2+, Cd2+, and Zn2+. These ligand-anchored materials, which were easily prepared from off-the-shelf chemicals in ca. 1 h, were hydrophilic and thus may give potentially fast kinetics of metal upload and removal (from the gels) in aqueous solutions. The ligand-anchored sol gels loaded with Cu2+ ions were regenerated with acid, and the materials could then be used in subsequent metal removal cycles. The effect of the reaction conditions [catalysts, ligand/Si(OMe)(4) ratios, and curing temperatures] on sol-gel properties and performance were investigated. In addition, the kinetics of Cu2+ upload and removal by these ligand-anchored sol-gel materials were studied. The work here shows that these hydrophilic ligand-anchored sol-gels are a good alternative to ligand-anchored organic polymers for toxic metal separation.