Geopolymer is an emerging “green” cementitious material which has a potential to valorize waste such as rice hull ash (RHA). Geopolymer is a kind of alkali-activated material which forms from the reaction of alumino-silicates in an alkaline solution. This study uses RHA as the raw material for alkaline activator while metakaolin (MK) serves as a geopolymer precursor to synthesize the so-called geopolymer sphere. Then its capacity as a porous matrix was explored upon incorporation of TiO2 nanomaterial using horizontal vapor phase growth (HVPG) technique to enhance its photocatalytic property. Indication suggests that the synthesized MK-geopolymer spheres activated with RHA-based water glass solution (WGS) were comparable to that of commercial WGS. Furthermore, the geopolymer spheres were successfully coated with TiO2 in the form of nanocrystals. Its photocatalytic activity was evaluated in terms of methylene blue degradation. This material’s potential environmental application for water purification and wastewater treatment will be investigated for future works.

Geopolymer spheres made from metakaolin and rice hull ash have exceptional chemical and mechanical stability, making them promising catalyst support matrix for photoactive compounds. In this paper, titania was deposited on geopolymer sphere via horizontal vapor phase growth method, which produced nanotitania crystals embedded on the surface. The titania-coated geopolymer spheres resulted in 90% dye photodegradation activity that can be used repeatedly, thus qualifying the products as sustainable materials for wastewater treatment.