Process for preparing high-purity nano silicon dioxide from rice husk

Abstract

The method for preparing nano silicon dioxide by utilizing rice husk includes the following steps: firstly, preparing inorganic acid treatment agent whose concentration is 1-20 wt%, according to the weight ratio of 2-50:1 adding rice husk, boiling for 0.5-3 hr., washing with water, drying, combusting rice husk for 15-180 min, at 600-900 deg.C, pulverizing combusted product to obtain the invented nano silicon dioxide whose grain size is 30-80 nm and purity is 98-99.9%. The used treatment agent is HCl or H2SO4, etc. The combustion heat or the rice husk can be recovered, and can be used as heat source for drying treated rice husk and also can be used as heat source for other application including heating and bathing pool.

Description

technical field [0001] The invention relates to a method for preparing nano silicon dioxide, in particular to a method for preparing nano silicon dioxide from agricultural by-product rice husks. Background technique [0002] my country produces about 200 million tons of rice per year, which is converted into about 40 million tons of rice husks, accounting for more than 30% of the world's total output, ranking first in the world. According to theoretical calculations, my country can extract about 800 tons of rice from rice husks every year. 10,000 tons of high-purity SiO 2 . It is a pity that rice husk resources are not fully utilized at present and are wasted as agricultural waste. Chinese patent ZL 86107192 is to use rice husk as raw material, under the condition of no external energy, slowly heat up in the roasting furnace, roast at low temperature, so that the organic matter in the rice husk is fully decomposed and gasified, so as to achieve whitening and combustion to p...

AI Technical Summary

Problems solved by technology

It is a pity that the current rice husk resources are not fully utilized and are wasted as agricultural waste

Chinese patent ZL 86107192 is to use rice husk as raw material, under the condition of no external energy, slowly heat up in the roasting furnace, roast at low temperature, so that the organic matter in the rice husk is fully decomposed and gasified, so as to achieve whitening and combustion to prepare silicon dioxide. In the method described in the invention, there are conditions that are unfavorable for industrialization such as large product particle size and high impurity content

Chinese patent ZL 95114827.3 introduces a production process for extracting silica with rice husk ash and boiler ash as raw materials, at a temperature of 140-170°C, a reaction pressure of 5-7MPa, and a reaction time of 4-5 hours Under the same conditions, chemical reaction with soda ash solution in a stirred reactor, the obtained product also has the disadvantages of large particle size and high impurity content

However, due to the change of the spatial structure of carbon and silicon dioxide during carbonization, the carbon cannot be completely burned during combustion, and the whiteness of silicon dioxide is not enough.

In order to completely burn the residual carbon, a higher combustion temperature is required, which makes the treatment process complicated, high energy consumption and high cost

Therefore, on the basis of our previous work, the present invention adopts chemical treatment of rice husk first, and then temperature-controlled combustion to prepare high-purity nano-silicon dioxide. This method has not yet been patented.