Professor James Economy's Group
Polymeric Ion-Exchange Fibers
This work explores the design of new ion-exchange materials in the form of fibers that yield a number of important advantages over conventional ion-exchange beads. In this approach, ion-exchange fibers are prepared by (1) coating low-cost glass fiber substrates with an appropriate oligomer, (2) cross-linking, and (3) functionalizing the coating to produce either anionic or cationic capability (see Figure 1 and Figure 2). As a result of the thin coatings, the use of solvents prior to both functionalization and preswelling of the finished product prior to end-use was eliminated, representing a significant simplification of current synthesis methods. Kinetic experiments showed that the contact efficiencies of these systems were greatly improved over the traditional beads because of the higher surface-to-volume ratio and shorter diffusion path lengths. This improvement translated into an order of magnitude increase in both ion-exchange and regeneration rates. Another advantage is the excellent resistance of the fibers to osmotic shock even after multiple regenerations (see Figure 3). Finally, these systems were shown to remove heavy metal contaminants ( Hg2+, Pb 2+ and arsenate ion )effectively to well below part per billion concentrations (see Figure 4-6).
Key Features as Compared to Beads:
(1/2 the steps)
Figure 1. Synthesis of cationic fibers on glass substrate
Figure 2. Synthesis of anionic fibers on glass substrate
Ion Exchange Fiber Selectivity
The primary research goals of this program are the tailoring and optimization of Ion Exchange Fiber (IEF) selectivity for monovalent over divalent species. This can be accomplished by incorporation of bulkier molecular architecture with the functional groups. Furthermore, by varying the size and functionality of the pendant molecules and inorganic groups respectively the degree and nature of the selectivity can be controlled. An immediate application of this technology is removal of nitrate and arsenate in the presence of sulfate. These ion exchange fibers are also being explored for removal of membrane foulants such as Humic acids other natural organic matter. Preliminary work has shown that selective ion exchange fibers can be produced as shown in the figure right comparing bulkier alkyl amine groups for selective anionic exchange.
1. Dominguez, L., J. Economy, K. Benak, C. Mangun, Anion exchange fibers for arsenate removal derived from a vinylbenzyl chloride precursor, Polym. Adv. Technol. 14, 632-637, 2003.
2. Dominguez, L., Z. Yue, J. Economy, C. Mangun, Design of polyvinyl alcohol mercaptyl fibers for arsenite chelation, Reactive and Functional Polymers 53(2-3), 205-215 2002.
3. Economy, J., L. Dominguez, C. Mangun, Polymeric ion exchange fibers, Industrial & Eng. Chemistry Research 41(25), 6436-6442, 2002.
4. Economy, J., C. Mangun, Novel fibrous systems for contaminant removal, In Sampling and Sample Preparation for Field and Laboratory, Ed. J. Pawliszyn, Elsevier Science, 2002.
5. Benak, K., L. Dominguez, J. Economy, C. Mangun, Sulfonation of pyropolymeric fibers derived from phenol-formaldehyde resins, Carbon 40(13), 2323-2332, 2002.
6. J. Economy. Now that's an interesting way to make a fiber! CHEMTECH 10(4), 240-7. 1980