Metal ion selectivity influences in polymer-supported reagents

Author

Cheryl E. Duffey

Date of Award

12-1998

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

Spiro D. Alexandratos

Committee Members

David Baker, Mark Dadmun, Larry Wadsworth

Abstract

The synthesis and characterization of numerous mono- and bifunctional coordinating and ion exchange resins were accomplished. A series of ethyleneimine polymers was synthesized and their abilities to complex metal ions from dilute solutions evaluated. A selective removal of Cu²⁺ ions in the presence of Fe³⁺ was noted from solutions of pH 2. Several factors were shown to influence the resin's ability to complex metal ions. An increase in the percent Cu²⁺ complexed corresponding to an increase in ligand length was observed and was attributed to the nature of the ligand. It was also noted that resins eluted with HCI exhibited greater percent Cu²⁺ complexed values than the same resins eluted with HNO₃. Introduction of a second ligand onto the ethyleneimine polymers had a profound impact on the percent Mⁿ⁺ complexed that did not follow the trends set forth by the monofunctional resins containing the same ligands. A series of phosphorus acid/ester mono- and bifunctional resins were prepared and their ability to complex Cd²⁺, Cu²⁺, Pb²⁺, Eu³⁺, and ³⁺ was investigated. It was shown that as the DVB crosslinking level was increased in phosphonic acid resins, the Eu³⁺ uptake decreased. Increased accessibility was demonstrated by macroreticular (MR) resins when compared to microporous (gel) resins for the uptake of Eu³⁺ by the same resins. The polymer supports to which -P(O)(OH)₂ ligands were covalently bound were shown not to be inert matrices, but exhibited a marked influence on the ligand's ability to bind the above metal ions from dilute solutions. In 0.1 N HNO₃ solutions, resin binding ability increased in the order: Phos (VBC) < Phos (STY) < Phosphoric. In addition a series of resins was prepared in which amidoxime ligands were covalently bound to differing polymer supports. These polymer supports were shown not to be inert matrices, but exhibited a marked influence on the ligand's ability to bind Cu²⁺ and Fe³⁺ from dilute solutions. In single metal ion studies binding ability of unsulfonated resins in 0.01 N HNO₃ followed the order: AN > Benzo > AN/STY (50/50) ≈ AN/STY (75/25). A preferential complexation of Cu²⁺ over Fe³⁺ was observed with the AN resins which became more pronounced during competition studies. Sulfonation of the Benzo and AN/STY (50/50) resins increased complexation of both Cu²⁺ and Fe³⁺, and a preferential complexation of ³⁺ over Cu²⁺ was observed in the competition studies with the sulfonated Benzo resin. A series of interpenetrating polymer networks was prepared in which the microenvironment around the vinylimidazole (Vim) ligand was altered. This altering of the microenvironment was shown to have a marked influence on the ligand's ability to bind Co²⁺. In single metal ion studies K₁₁ values increased in the order: AA < Vim &ly; VIm/AA (50/50) < VIm/EA (50/50). When Cu²⁺ ions were put into competition with Co²⁺ ions the K,, values (for Cu²⁺ complexation) followed the order: AA < VIm/AA (50/50) < Vim < VIm/EA (50/50). Finally, an evaluation of the Irving-Williams series of metal ion stability was performed using polymer-supported phosphonic acid ligands. Metal ion complexation abilities of the four polymers examined were found to follow the order: Co²⁺ < Ni²⁺ < Zn²⁺ < Mn²⁺ < Cu²⁺ < Fe²⁺. This observed order is not in agreement with the Irving-Williams series of stability for small molecule complexing agents which follows the order: Mn²⁺ < Fe²⁺ < Co²⁺ < Ni²⁺ < Cu²⁺ > Zn²⁺. It was also noted that although the complexing ligand in each resin was phosphonic acid, the percent complexed values increased in the order: VBC/MMA < STY < VBC < Acetyl.

Recommended Citation

Duffey, Cheryl E., "Metal ion selectivity influences in polymer-supported reagents. " PhD diss., University of Tennessee, 1998.
https://trace.tennessee.edu/utk_graddiss/9237