A study on the consecutive preparation of d-xylose and pure superfine silica from rice husk

Rice husk is an abundant agricultural byproduct. In the present paper, research on consecutive preparation of d-xylose and superfine silica from rice husk is carried out. The optimum hydrolysis conditions of xylan in rice husk to d-xylose are as follows: the concentration of H2SO4 is 4% (wt.%), the temperature is 130 °C, the ratio of rice husk mass (g) to H2SO4 solution volume (ml) is 1:4 and the time is 2 h. The hydrolysis degree of xylan reaches 96.22% (wt.%). High purity (98.5%, wt.%) d-xylose is obtained from acid hydrolysis solution with the purification yield of 71.63% (wt.%). At the same time, the metal oxides in rice husk are efficiently dissolved by H2SO4. Residuals from H2SO4 pre-treatment are incinerated under 750 °C in stationary air for 15 min. Silica is obtained with the purity of 99.87% (wt.%). The superfine silica powder is obtained after ground and ultrasonic dispersion, with the diameter of 30–200 nm and specific surface 287.86 m2/g.