The Method of Obtaining Amorphous Nanosized Silicon Dioxide from Rice Production Waste

Abstract

The method of using rice husk, which is a rice production waste, as a raw material for the production of silicon dioxide as an alternative to synthetic silicon dioxide – aerosil is considered. A low-energy process for extracting silicon dioxide and cellulose from the husk by alkaline digestion in an NaOH solution was proposed, followed by treating the black liquor with an acid solution and calcining the precipitate at 575 °C during 5 hours. The yield of inorganic products from rice husk is determined based on the ash content of the pulp. It was shown that the product obtained mainly consists of silicon dioxide (SiO2) of amorphous structure, has an average particle size of less than 100 nm, which makes it possible to characterize it as nanosilica. At the same time, silicon dioxide consists of 51.7 % silicon and 48.3% oxygen against theoretical amounts of 30.4 % silicon and 69.6 % oxygen, respectively. The output of silicon dioxide is 8.8 % by weight of rice husk. At the same time, the process allows to obtain another valuable nanocellulose product.