Doctoral Dissertations

Date of Award

8-2000

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

Spiro Alexandratos

Committee Members

Mark Dadmun, Ben Xue, Gajanan Bhat

Abstract

The focus of this research has been the design and development of polymeric reagents with enhanced ionic accessibility for application to separation science. Ion-complexing ligands were then coupled with polymeric foams, polystyrene beads, and high stability solvent impregnated resins (SIRs). The polymers were evaluated for their metal ion affinity.

Four ligands were supported onto the polymeric foams prepared with 8% and 15% crosslinking. The ligands studied were monophosphonic acid, diphosphonic acid, a-ketophosphonic acid, and p-ketophosphonic acid. The functionalized foams were studied for their ability to complex Cu(n), Fe(in), and Eu(III) in batch studies followed by column studies. The highly crosslinked foams were able to be functionalized as one solid piece. The foams demonstrated uniform functionalization throughout the polymer, making them applicable for a wide range of studies. Functionalized foams performed much better than beads in columns with the same type of ligands. This showed the increased porosity does increase the accessibility of the metal ion into the polymer matrix. Further research is needed to better understand reproducibility and regeneration of the functionalized foams.

Increased accessibility of metal ions into polymer beads was evaluated by three methods. The first method was to increase the surface area by studying the complexation of the metal ions at two different bead sizes. This did not increase the accessibility. Complexation of the four metals studied [Cu(n), Pb(n), Cd(n), and Eu(in)], was comparable. The second method was to increase the porosity by comparing microporous beads to macroporous beads. The change in polymer support also did not increase the percent complexed of the metal ions for the ligands studied. The final method was the idea of dual-mechanism bifunctional polymers. The addition of a recognition ligand to the resins increased the percent complexed dramatically to >90% for all the metals studied.

High stability SIRs were synthesized and studied to evaluate the effect of complexation time and porosity of the polymer support on the percent complex. SIRs were found to have rapid rates of complexation since decreasing the contact time from 24 hours to 15 min did not affect the percent complexed. Encapsulated SIRs complexed >90% over six contact/regeneration cycle. The SIR maintained a higher percent complexed at 15 min for longer contact periods in comparison to the 24 h study. Decreasing the porosity of the support matrix did not significantly affect the percent complexed for the encapsulated SIR.

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