Abstract: Nano-sized silica (nano-SiO²) was prepared by improved chemical precipitation method including the processes of acidification,aging,washing,filtering and so on from rice husk ash.Technological process of preparing rice husk ash used rice husk as raw material and contained the pretreatment and energy recovery by the combustion.Experiment can recycle the burning heat and maximize the use of rice husk.Effects of several reaction factors,such as pH of the reaction system,concentration of sodium metasilicate,concentration of sulfuric acid,and reaction time,on the process of reaction were investigated and optimum conditions were confirmed as follows:pH of the reaction system was 8,concentration of sodium metasilicate was 0.30 mol/L,concentration of sulfuric acid was 0.5 mol/L,and reaction time was 45 min.Under the optimum conditions,the products were characterized for many times and results showed: the product was amorphous silica,distribution of particle size was at 50~100 nm,average particle size D50 was 72 nm,specific surface area was 191.86 m²/g,white content was 94.6%,and silica purity was 98.6％. 

Key words: rice husk, nano-SiO², improved chemical precipitation