Synthesis of porous silica from wasted SiO₂-containing molding compounds

Materials: In this study, we provided a simple method to extract the silicate species from the waste silica-containing molding compounds from the semiconducting industry. Methods: Recycled sodium silicate solution was obtained from alkaline extraction of the silica fillers in the waste molding compounds and dried and redissolved in appropriate amount of water. Results: Porous silica of high surface area (>500 m²g⁻¹) and tunable pore size (1.5–5.0 nm) could be feasibly synthesized by using the recycled sodium silicate as silica source and nature-friendly homopolymer polyethylene glycol (PEG) as an organic template. The pore size of the PEG-templating silicas was made tunable by hydrothermal treatment at different pH. Conclusion: To reduce the emission of CO₂ gas from the removal of the PEG template, porous silica with a large surface area has been prepared at a low PEG/sodium silicate weight ratio of 1/20.