Carbonation of Alkali-Fused Ash from Biomass Power Plants: A Novel Approach for High Extraction Yield of Nano-Silica

This study produces high-purity nano-silica from corn straw ash (biomass power plants) using an alkaline fusion-derived sodium silicate solution. CO2 replaces traditional acids in the carbonation reaction, enabling high extraction yield (93.11%). The process addresses the gap in directly utilizing combustion ash for such high-purity silica. Key optimal conditions identified were 5 M aq. HCl concentration, NaOH fusion reagent, 1:1.2 mixing ratio, 3 M aq. NaOH solvent, and 12 h ripening. The resulting nano-silica achieved 92.73% purity, 10–50 nm particle size, 270 × 10−5 m3/kg dibutyl phthalate (DBP) absorption, 55.9916 m2/g specific surface area, 6.38% loss on drying (LOD), and 6.69% loss on ignition (LOI). These properties meet national standards for premium, loosely structured nano-silica. This method provides an economical and effective silicon source, reducing costs and offering economic-environmental benefits.