Development of tri-modal-pore architecture of silica monolith via extrusion-based 3D printing and employing rice husk ash

The ability to lightweight micro-macroscopically shape porous silica monolith while concurrently tailoring the porous structure as desired by environmentally and facile processes is essential in advanced ceramics. In this study, we present a sustainable strategy to fabricate amorphous silica toward deliberately three different sizes of organized pores utilizing waste rice husk ash (RHA) and extrusion-based 3D printing. First, organic template-impregnated silica particles were synthesized from RHA by the alkali-extraction method, and the surface morphology and size of the extracted particles were comprehensively analyzed. Second, a viscoelastic ink was designed using an ether solvent with dispersant, and direct ink writing log-pile structures were heated at 600 °C. Finally, the fired specimen achieved a porosity of ∼89% with different shapes of pores (2 nm-450 μm), which are generated by 3D printing and burning of organic solvent and template. This lightweight biogenic-silica foam with tailorable pore formation feasibility has potential applications in separation, adsorption, catalysis, and controlled drug release.