Abstract

Rice husk ash is one of the most silica rich raw materials containing about 90 – 98% silica after complete combustion among the family of other agro wastes. Ash samples from rice husks of five different origins were prepared at two different temperatures, 500 and 1000^oC, respectively and the ash content was evaluated at each temperature. The interestingly high percentage of silica (taking up from the soil during paddy growth) in rice husk ash which has various industrial and domestic applications necessitated the process of determining the presence and amount of impurities or trace elements in ash taking up from the soil during paddy growth. Small quantities of impurities present at concentrations below one part per billion can have a significant effect on the quality of devices constructed form the silica obtained from the ash. The X – Ray Fluorescence (XRF) technique was used to analyze each sample heated to a temperature of 1000⁰C at which excellent chemical activity could be exhibited to characterize the ash in terms of the purity of the silica level by the determination of the trace (impurity) elements present that has a nature that can determine their removal method to get the pure silica. The result of the XRF showed that rice husk ash (RHA) had a very low impurity concentration of 1.1 (sample 1) to 5.58% (sample 4) corresponding to 98.9% (sample 1) and 94.42% (sample 4) purity level of silica indicating that rice husk which is an agricultural waste is a potential source of silica with a high purity level of 94 - 98.9%.

Key words: Rice husk, ash composition, fluorescence, impurity, silica.