Studies on the formation of black particles in rice husk silica ash

The formation of black (carbon fixed) particles in rice husk silica ash has been studied in detail. The formation of black particles in the silica obtained by calcination of raw untreated rice husks, is higher than that in acid treated rice husks. The tendency to form black particles increases with increase in the heating rate and the temperature of calcination of the untreated rice husks. Potassium has been shown to cause the formation of black particles in rice husk silica. By treating with 3.0 N HCl acid the formation of black particles can be avoided. There is no effect of heating rate on the formation of black particles in silica from acid treated rice husks. Treatment with HCl acid was found to decrease the oxidation (burning) of carbon at lower temperature (400 degreesC). (C) 2000 Elsevier Science Ltd. All rights reserved.