Effect of nitric acid digestion on organic materials and silica in rice husk

Abstract

Studies on the digestion of rice husk by HNO 3 at 65 °C over 2–12 h have been carried out. Changes in the physical characteristics and morphology of rice husk due to the degradative effect of nitric acid were studied by using thermogravimetric analysis and scanning electron microscopy. It was observed that the residue obtained after 12 h digestion is a mixture of loose cellulose fibres and fragments of a cellulose–silica composite consisting mainly of cellulose (ca. 24%) and silica (ca. 76%), respectively.