Preparation of low surface area SiO2 microsphere from wheat husk ash with a facile precipitation process

• Preparation of mesoporous SiO2 microspheres with low surface area from wheat husk ash.
• Volume ratio of extract, water and ethanol affects SiO2 microsphere size distribution.
• The specific surface area of silica microspheres controlled by addition rate of HCl solution.

Low surface area SiO2 microspheres with narrow size distribution are prepared from wheat husk ash with a facile precipitation process, in which four steps including the extraction of sodium silicate, the dilution of sodium silicate extract with distilled water and ethanol, the precipitation of silica with HCl solution and calcination process are involved orderly. The particle size distribution and the specific surface area of the resulted silica microspheres are affected predominantly by the volume ratio of extract, water and ethanol and the dripping rate of HCl solution. The synthesized SiO2 microspheres with internal mesopores have an amorphous structure with diameters of approximately 227 nm and a specific surface area of 8.23 m2/g under the optimized synthesis conditions with a volume ratio of 1:1.5:0.5 for extract/water /ethanol and HCl solution dripping rate of 3 mL/min.