Preparation and characterization of organofunctional sol-gel materials and their application in toxic metal separation

Inorganic-organic hybrid SiOz sol-gels anchored with amino (NHz-CHzCHz-NH-, TMSen, and -NH-CH2CH2-NH-, Bis-TMSen) and mercapto (HS-) ligands have been studied as new sorbents for heavy metal (e. g., Cu2+, Hg”, Cd2+, Zn2+, and Ni2+) separation. The TMSen—anchored gels were found to be selective for Cu” removal in the presence of Cd2+ and Zn”. In comparison, mercapto-anchored gels remove both Cu2+ and Cd2+ from a mixture of Cu”, Cd2+ and Zn”. These ligand-anchored materials, which were easily prepared fi'om off-the-shelf chemicals in ca. 1 hr, were hydrophilic and thus showed fast kinetics of metal uptake and removal (from the gels) in aqueous solutions. The ligand-anchored sol gels loaded with metal 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, curing temperatures, and surfactant existence] on sol-gel properties and performance were investigated. In addition, the kinetics of Cu2+ uptake and removal by these ligand-anchored sol-gel materials were studied.