Sulfonation of pyropolymeric fibers derived from phenol-formaldehyde resins Original Research Article

This research demonstrates that pyropolymeric fibers derived from phenol-formaldehyde resins can be successfully sulfonated providing advantages that are not currently available with traditional polymeric ion-exchangers. Benefits of this system include higher thermal stability, elimination of osmotic shock associated with beads, and enhanced ion-exchange capability. In this study, a series of thermally and chemically activated fibers were prepared by heating a phenolic precursor under inert atmosphere at temperatures between 350 and 600 °C. Subsequent sulfonation of the fibers in concentrated sulfuric acid incorporated sulfonic acid units as well as various oxygen-containing groups. The identification of functional groups and their thermal stability was carried out using elemental analysis (EA), diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), and thermal gravimetric analysis (TGA). The effect of sulfonation on pore volume and surface area is discussed. Functional groups added during the sulfonation process serve as either strong acid or weak acid cationic exchangers.