Calorific value of the raw material was found by ASTM D5868-10a. The kaolin clay used in this experiment is procured commercially from Chemtex Corporation, Kolkata, India. The modification of kaolin using nitric acid of 3 M concentration was carried out by adding 50 g of the kaolin clay to 500 ml of nitric acid solution of 3 M concentration and refluxing at 110 C under the atmospheric pressure in a round bottomed flask equipped with a reflux condenser for 4 h.