Funtionalized 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.