Novel modification method to prevent tailing behaviors within synthetic resin adsorbents

Abstract

Synthetic resin adsorbents comprising styrene-divinylbenzene copolymers are widely used in different fields such as pharmaceutical and food industries. Especially phenolic compounds are commonly adsorbed by resin adsorbents. However, resin adsorbents show a tailing behavior in fixed-bed operation, a phenomenon caused by slow mass transfer in the particles, and as a result, the adsorbed molecules cannot be desorbed completely (irreversible adsorption). Earlier studies revealed that reversible and irreversible adsorption of resin adsorbents were caused by macro- and micropores, respectively and proposed modification techniques to reduce the irreversible adsorption by use of styrene molecules. Intraparticle diffusivity of adsorbate molecules in adsorbents is necessary for design of industrial separation/recovery process. The earlier study, however, did not discuss the effect of styrene modification on the intraparticle diffusivity. From a point of practical view, not only reducing irreversible adsorption but also increasing or remaining intraparticle diffusivity after modification is required. As a result, the effect of intraparticle diffusivity of phenol molecules in the synthetic resin FPX-66 before/after modification was investigated in this study. Based on the result of previous modification technique, styrene molecules were adsorbed only in micropores by long-term adsroption and short-term desorption process and polymerized in micropores to block adsorbed molecules. The intraparticle diffusivity was determined by circulating-type fixed-bed adsorber (CFBA) technique, which is the application technique of completely mixed batch reacter (CMBR) method. The result indicated that modified FPX-66 with styrene showed no tailing behavior, and doubled intraparticle diffusivity. Therefore the modification technique is useful for increasing the efficiency of industrial separation/recovery process.