Langmuir 1999, 15, 8300-8308
Anion-Exchange Properties of a Mesoporous Aluminophosphate
Dean A. Kron, Brian T. Holland, Robert Wipson, Caroline Maleke, and Andreas Stein*
Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
<>A mesoporous aluminophosphate support, meso-AlPO,
was synthesized by phosphate treatment of an AlO4Al12(OH)24(H2O)7+
cluster/dodecylsulfate salt, followed by extraction of the surfactant
with an acetate/methanol solution. The meso-AlPO product was shown to
be an effective anion-exchange material. Anion-exchange capacities for
chromate and several monoanionic and dianionic organic dyes fell in the
range from approximately 1.3 - 1.6 meq/g. Control experiments with the
neutral support MCM-41 and a nonionic dye indicated that anion
adsorption in meso-AlPO was caused predominantly by electrostatic
interactions rather than pure physisorption. Multiple exchanges were
possible if the support was regenerated by acid treatment at pH 4.3.
While the material exhibited size-selectivity for anionic dyes, the
average pore sizes increased during anion-exchanges in aqueous
solutions. The mesopore structure of meso-AlPO was thermally stable up
to 200 deg. C, and anion-exchanges at 100 deg. C under aqueous reflux
resulted in similar exchange capacities as room temperature exchanges.