| Rice husk has been used for preparation of chemically
pure and amorphous silica. When husk is heated in air, the
resulting silica ash varies in colour from grey to black and
contains inorganic impurities along with unburnt carbon.
The ash, if further heated, resulted in formation of crystalline
forms of silica. However, by treating the husk with
nitric acid followed by heating in air, pure white amorphous
silica was obtained. A possible explanation for the
ready removal of carbonaceous matter through this route
has been advanced. |
