Abstract

Macroporous cation-exchange resins can be synthesized by sulfonation of poly(styrene-co-divinylbenzene) microparticles. The degree of sulfonation attained, and hence their cation-exchange capacity, depends on factors related to the polymerization process, such as the percentage divinylbenzene (%DVB) and of the monomeric fraction added to the polymerization mixture (Fm), as well as on variables related to the sulfonation process itself, such as temperature and time of sulfonation. Mass transfer of the sulfonation agent by diffusion inside the microparticles is governed by different diffusion mechanisms due to the existence of gel-type nanoparticles and pores of very different sizes inside them. Detailed modeling of these processes is difficult, but the use of simplified models addressing the diffusion of a liquid into a spherical solid seems to be suitable for the process to be described. Thus, in the present work experiments aimed at determining the sulfonation kinetics of polymeric microparticles were performed. After attempting to fit some of the most widely used models to our experimental results, it was found that a polynomial model used to study the kinetics of ion-exchange processes is also useful to explain the kinetics of the sulfonation process.