MECHANOCHEMICAL METHOD OF PROCESSING SILICA-CONTAINING PLANT MATTER

Abstract

The possibility of complex processing of silica-containing plant biomass with the selection of a line of target products is investigated. The method includes the mechanochemical treatment of biomass in a solution of sodium hydroxide in a rotary pulsation apparatus at a temperature of self-heating not lower than 80 °C. The resulting suspension is separated on a solid residue and an extract. The solid residue is washed and dried to obtain pulp powder. The bio-filled silica gel with an SiO2 content of 49.4 wt.% to 62.6 wt.% is isolated from the extract after separation of the solid residue. By ashing the silicon-containing product at a temperature of 600 °C, amorphous silica is obtained. The content of SiO2 (as the target component) in the ash is 85.5–92.0%. The SiO2 diffraction pattern is characterized by the presence of a diffuse halo with a maximum at 2q=22.75 ° and the absence of diffraction peaks. Preliminary acid leaching can increase the purity of the resulting silica to 99.0%. The specific surface area of the obtained silica was determined by the BET method for nitrogen sorption at 260 m2/g.
 The effect of the concentration of the extractant on the yield of alkali-soluble substances and the degree of leaching of silicon was studied. It was shown that even at a 1% concentration of the extractant (NaOH), almost complete leaching of silicon from the plant matrix occurs. Depending on the increase in the concentration of NaOH, the degree of delignification of the biomass increases to 13–18–22%, respectively, with an increase in the concentration of NaOH 1–5–10%. Powdered cellulose was obtained with a content (%): silicon – 1.12, lignin – 34.8, alpha cellulose – 86.0, with a yield of 33.0% and a particle distribution of 80–300 μm. The amount of biomass loss is 17.6 wt.%.