NANO-STRUCTURED SILICA FROM RICE HUSK

The potential and limits of rice husk to become a competitive source of nano-structured silica were investigated. Husk samples were submitted to a chemical pre-treatment using celluclase enzyme, NaOH, HCI, or H2SO4 solution. Subsequently, samples were incinerated at 600-degrees-C under static and flowing atmospheres (air, oxygen, or steam). The product was characterized in terms of silica content, particle size distributions at different levels of agglomeration, and specific surface area (BET, N2). A product with properties intermediate to those of fumed silica and xerogel was 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-mu-m. The specific surface area for the primary particles reaches values of 250 m2/g. Purity is better than 99.8% silica.