Molecular imprinting of organofunctionalized sol-gel materials for metal ion separations

Author

Mark Charles Burleigh

Date of Award

8-2000

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

Ziling Ben Xue

Committee Members

Sheng Dai, Mark Dadmun, Paul Bienkowski

Abstract

This dissertation describes the synthesis and characterization of new metalion sorbent materials. These materials exhibit many favorable properties such as high metal ion capacities, metal ion selectivity, fest kinetics, and easy regeneration. Sorbents have been developed to selectively adsorb Cu(II),Zn(II),and Ni(II) cations.

A combination of four primary synthetic techniques were used to create mesoporous sorbents with specific adsorption characteristics. The hydrolysis and condensation of silicon alkoxide precursors via sol-gel reactions leads to the formation of a solid matrix. Bifunctionalreagents were used to graft amine moeities to the solid support and give the sorbent a high affinity for metal ions. Molecular imprinting techniques were used to create metal ion binding sites that are designed to bind to a specific metalion. The surfactant template approach was used to engineer the porosity of the sorbents.

Four new methodologies have been developed and described herein: imprint double imprinting, and organic-inorganic polymer imprinting. The imprint coating technique involves grafting of metal ion complexes of bifunctional reagents to the surface of mesoporous silica. Acid leaching of the metal ion template results in the formation of selective binding sites in which the ligands are arranged in a conformation well suited to rebind the template. In stepwise assembly. the bifimctional reagent is first grafted to mesoporous silica, followed by metalion complex formation and the addition of more bifimctional reagent. In the double imprinting methodology, metal ion complexes of bifunctional reagents undergo copolymerization with silicon alkoxide precusors in the presence of supramolecular assemblies of surfectant molecules in a single step synthesis. Surfectant extraction gives a porous matrix with alarge surfece area. Hybrid organic-inorganic sorbents were synthesized using a protocolsimilar to double imprinting, except that the sol-gel precursor used was a bridged silicon alkoxide containing an ethylene group.

These sorbent materials have been characterized bya variety of techniques Including: ^29Si solid-state nuclear magnetic resonance spectroscopy, N2 adsorption. powder X-ray dffiaction, UV/visible spectroscopy, and batch testing with subsequent ICP/OES analysis. These organofimctionalized sol-gel materials exhibit a number of fevorable properties mcluding: enhanced capacities for the target metal ion, selective adsorption oft he target metalion from mixed solutions containing competitor species, fast metalion uptake kinetics, and easy regeneration.

Recommended Citation

Burleigh, Mark Charles, "Molecular imprinting of organofunctionalized sol-gel materials for metal ion separations. " PhD diss., University of Tennessee, 2000.
https://trace.tennessee.edu/utk_graddiss/8234