Fabrication of interconnected macroporosity in geopolymers via inverse suspension polymerization

Abstract

AbstractA new approach to fabricate geopolymer monoliths with interconnected macroporosity and a permeable structure is presented. This was achieved using an unconventional route of inverse suspension polymerization in which the aqueous geopolymer slurry consisting of potassium hydroxide, fumed silica, and natural metakaolin was dispersed in a continuous phase of soybean oil. The geopolymer monolith was synthesized by taking advantage of the so‐called “sticky period” that occurs during inverse suspension polymerization. During this period, individual droplets can coalesce but cannot re‐divide because of the partially polymerized matrix. We deliberately brought the partially polymerized geopolymer particles in proximity during the sticky period to fuse the particles. Hence this method, termed as “sticky period particle fusion,” helped to form a monolithic structure with inter‐particle spacing as macropores which resulted in high permeability. The sticky period was observed to depend on synthesis conditions such as stirring speed, temperature, and viscosity of continuous phase which in turn helped to tune the surface and pore properties of geopolymer monoliths. The BET surface area up to 67 m2/g and total pore volumes of 0.4 cm3/g from pycnometry were obtained.