Synthesis and Applications of Monolithic Ion Exchange Resin

Abstract

We have synthesized a new type monolithic porous ion exchange resin which has a co-continuous porous structure. The pore structure is obtained by a two-step polymerization process. In the first step, an open-celled porous styrene-divinylbenzene (St-DVB) copolymer is synthesized by preparation of waterin-oil (W/O) emulsion and polymerization. In the second step, the obtained copolymer is soaked and polymerized in a solution containing a polymeric initiator, styrene and DVB. In order to obtain the monolithic ion exchange resin, functional groups, such as sulfonic acid and trimethylammonium, were introduced into the copolymer. The ion exchange capacities of the monolithic cation and anion exchange resins that have co-continuous porous structures were both over 4 meq/g. The pressure drop of the new monolith was about 5 times lower than that of previously reported open-celled monoliths. The ion exchange band length of the new monolith was about 10 times shorter than that of conventional ion exchange resins. As one application of the new monolith, we have developed a palladium-loaded monolithic anion exchange resin (Pd-AEMR) to decompose hydrogen peroxide (H 2 O 2) in ultrapure water. TEM and EPMA data indicated that Pd particles of about 50 nm were loaded uniformly on the surface layer of Pd-AEMR. H 2 O 2 decomposition rate when using Pd-AEMR was about 10 times faster than that of Pd-loaded bead-type resin.