Perspectives of the Silicon Dioxide Production from Rice Husk in Kazakhstan: an Overview

Abstract

Rice husks (RHs) are the hard-protecting coverings of grains of rice. Considering the fact that this agricultural waste accumulates over the years, the need for prompt resolve for RH waste is readily apparent. As claimed by the Food and Agriculture Organization of the United Nations (FAO), the production of the global paddy rice in 2016 is considered to be 748.0 million tons. Based on this, the amount of RHs makes up about ~20% of paddy rice production by weight. Much of this production is treated as waste and either thrown into rivers or tossed on landfills, often causing pollution problems when it decays or simply returned to the fields where it can become airborne. This work presents synthesis routes for the production of SiO₂ from RH sourced in Kazakhstan. RH, chosen from Almaty, Kyzylorda and Turkystan regions, was utilized as the major silica source. The results shown verified that the highest purity (98.2–99.7%) amorphous silica with a certain surface area between 120–980 m² g^-1 could be extracted during acid treatment and controlled calcination. The structure is amorphous, porosity diameter reduced from 26.4 nm to 0.9 nm, certain pore volume raised from 0.5 to 1.2 cm³ g^-1.