稻壳制备纳米二氧化硅新工艺研究

New technology for preparation of nano-sized silica from rice husk

研究以稻壳为原料,经过预处理、燃烧回收能量后获得稻壳灰,再以稻壳灰为原料,采用改良化学沉淀法,经酸化、陈化、洗涤、过滤等过程制得纳米二氧化硅。实验过程中可以回收稻壳燃烧的热能,并对废弃稻壳最大化利用。实验考察了沉淀反应体系pH、偏硅酸钠浓度、硫酸浓度、反应时间等因素对反应过程的影响,获得了较适宜的工艺条件：反应体系pH为8,偏硅酸钠浓度为0.30 mol/L,硫酸浓度为0.5 mol/L,反应时间为45 min。并对此条件下制备的产物进行多方面表征,表征结果为：所得产物为无定形二氧化硅,粒子粒径分布在50-100 nm,平均粒径D50为72 nm,比表面积为191.86 m^2/g,白度为94.6%,二氧化硅纯度为98.6%。

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%.