Grantee Research Project Results
Investigation of Ion Transport and Selectivity Achieved With Crown Ether Fixed-Site Carrier MembranesEPA Grant Number: U914986
Title: Investigation of Ion Transport and Selectivity Achieved With Crown Ether Fixed-Site Carrier Membranes
Investigators: Thunhorst, Kristin L.
Institution: University of Colorado at Boulder
EPA Project Officer: Jones, Brandon
Project Period: January 1, 1996 through January 1, 2000
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1996)
Research Category: Academic Fellowships , Engineering and Environmental Chemistry , Fellowship - Chemical Engineering
The objectives of this research project are to: (1) address how ion transport through crown-ether-containing membranes is affected by the membrane and carrier properties; and (2) analyze the role of the structural and material properties.Approach:
This study has focused on fixed-site carrier membranes-solid polymeric membranes with crown ether functionalities polymerized into the polymer backbone. The solid membranes were mounted in a transport cell, and experiments with varying aqueous solutions have been conducted. The ion transport of potassium, sodium, rubidium, and cesium through membranes of varying composition has been investigated to date with some single-component and some multicomponent experiments. The effect of the anion, which accompanies potassium also has been investigated. In our studies, we have seen that the flux of the potassium cation is affected by the anion accompanying its transport through the solid membranes, but in a completely contrary trend to that observed with the liquid membrane systems. The experiments have been conducted using membranes with 73.1-73.6 percent VB18C6 and 2.0-2.1 percent hexamethylene diacrylate in the monomer mixture. Experiments have been completed that investigate the transport (through the fixed-site membranes) of potassium and sodium ions with the following counter ions: nitrate, perchlorate, triflate, and chloride. We have seen that the transport rate of potassium is greatest when nitrate or chloride is the counter anion than when perchlorate or triflate salts were employed. This is completely counter to the observations that have been made with liquid membrane systems (increasing flux with increasing -GA).Supplemental Keywords:
fellowship, ion transport, fixed-site carrier membranes, potassium ions, sodium ions, ion selectivity.