Design of high efficiency polymeric cation exchange fibers

In this study we have been exploring a new ion exchange material in the form of a fiber that could 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 a polystyrene/divinylbenzene oligomer, 2) curing, and 3) sulfonating. The sulfonation process and effects of varying degrees of crosslinking were characterized through diffuse reflectance infrared spectroscopy and acid-base neutralization titrations. Capacities of 4.7 meq/g (on a per resin basis) were easily obtained. Kinetics experiments showed the contact efficiencies of the new systems were greatly improved over the traditional beads due to greater surface associated with the pm morphology and shorter diffusion lengths. This translated into an order of magnitude increase in ion exchange rate. As a result of the thin coatings, the use of solvents prior to functionalization, and preswelling of the finished product prior to end-use were eliminated. Scanning electron microscopy was used to image the fibers and track their mechanical integrity through various stages of the process. Finally, repetitive regenerations proved the long-term stability of the spent fibers. Copyright (C) 2001 John Wiley & Sons, Ltd.