Preparation and characterization of high-grade silica from rice husk

Abstract

The potential and limits of rice husk to become a competitive source of nano-structured silica are investigated. Husk samples are submitted to a chemical pre-treatment using celluclase enzyme and different inorganic acids. Subsequently. samples are incinerated at 600°C, 6 h under static atmosphere. The product is characterized in terms of silica content, particle size distributions at the different levels of agglomeration, and specific surface area (BET, N2). With pre-treatment acids. (HCL (1:4) or H2 S04 (1:4)) a product with properties intermediate to those of fumed silica and xerogel is obtained. The size distribution for secondary particles follows a log-normal distribution with d50 = 26 nm and d84/d16 = 2. Tertiary agglomerates range from 0.3 to 30 um. The specific surface area is determined by the primary particle and reaches values of 250 m2/g. Purity is 99.4% silica.