Effect of silica and lignocellulosic additives on the formation and the distribution of meso and macropores in foam metakaolin-based geopolymer filters for dyes and wastewater filtration

This work investigates how silica and lignocellulose additives affect the production of metakaolin based-geopolymer foam filters. Lignocellulosic material from wood powder sawdust (S), silica from rice husk ash (RHA), calcined (Sa) and uncalcined (Sab) sand were separately used together with high amorphous silica fume (FS) (foaming agent) and integrated into the matrix (metakaolin and solution). The different geopolymer pastes were cured at 70 °C to enhance the pore formation. Results presented the geopolymer foams filter as sponge-like composites having 58-68 % of porosity with 1-4 MPa of compressive strength. RHA and Sa lead to materials with more meso and macropores. Sawdust based-geopolymer (the hardest foam) containing channel pores predominated by coarse pores exhibited a flow rate of 4 mL/min. The absence of the bands of MB from FT-IR spectra and UV spectra (663 nm) of MB filtrate (totally blue discoloured) indicated that, geopolymers foams filters designed are suitable for dyes and wastewater filtration.