Ceramic Microbeads as Adsorbents for Purification Technologies with High Specific Surface Area, Adjustable Pore Size, and Morphology Obtained by Ionotropic Gelation

In this study, we present an ionotropic gelation route for obtaining porous alumina/silica microbeads ( MB s) with tailorable morphology, specific surface area ( S BET ), and pore size, which can directly be sintered into porous, monolithic adsorbents ( MAd s). After sintering, S BETs from 20 m 2 /g up to 70 m 2 /g with open porosities up to 90% could be achieved depending on the silica nanoparticle addition. Due to the significantly increased S BET , a more than 100‐fold faster uptake of model dye molecules was obtained. Pore sizes ranged between 13 and 184 nm with adjustable mono‐ and bimodal size distributions. Depending on silica content and sintering temperature, the MB s were also found to be chemically stable in technologically relevant solvents such as water, acetone, acetonitrile, hydrochloric acid, and methanol for at least 1 week except for sodium hydroxide. By adjusting the processing parameters, spherical, fibrous or irregular microbead morphologies could be obtained. The same route was also successfully applied for obtaining calcium phosphate, titania, and zirconia microbeads. The presented straight‐forward ionotropic gelation route is basically applicable to any other ceramic material and therefore extremely versatile. The obtained MB s and MA ds can be further adapted to any type of environmental or biotechnological purification process by additional functionalization steps.