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. 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. Finally, these systems were shown to remove heavy metal contaminants effectively to well below part per billion concentrations.