105 Physical Properties and Content of Silica in Different Varieties of Rice Husk Found.... Physical Properties and Content of Silica in Different Varieties of Rice Husk Found in Sri Lanka RMS Virajini, VPS Perera and JCN Rajendra * Department of Physics, The Open University of Sri Lanka, Nawala, Nugegoda, Sri Lanka jcraj@ou.ac.lk * ABSTRACT Rice Husk (RH) is one of the main agricultural wastes available abundantly in Sri Lanka. Physical properties such as moisture content, average bulk density and porosity of seven varieties of RH found commonly in the western province of Sri Lanka were studied in this research. Moisture content varies between 10.38% -12.80%, the average bulk density varies between 372.90 kg m -3 - 523.94 kg m -3 and the porosity varies between 46% - 68% of these samples. The highest amount of silica was estimated as 98.2% for BG300 variety of RH and the lowest amount of silica was estimated as 78.3% for Suwandal variety of RH. A typical SEM image and XRD analysis was done to characterize the extracted silica from Rice Husk Ash (RHA). Considerable reduction in particle size of silicain RHA from 10.1 Å to 8.10 Å was observed after the synthesis process. 1.0 INTRDUCTION Rice is the staple food of the inhabitants of Sri Lanka. The total land devoted for paddy is estimated to be about 708,000 Hectares at present. On average 2 – 3 million metric tons of paddy is produced annually in Sri Lanka 1 . Percentages of husk in paddy vary widely between 14 % - 27 % according to the geographical location and variety, but 20% can be taken as a fair average. An analysis in Sri Lanka showed about 22 % of paddy mass is Rice Husk (RH) 2 . RH is commonly used as a fuel for household, operating rice mills and as an animal feed. Considerably large amount of RH is burnt to ash creating a great environmental threat that causes damage to the land and the environment in which it is dumped. Disposal of this Rice Husk Ash (RHA) is a great challenge. Lots of ways are being studied by the researchers to transform this RHA into a viable commercial product. Over the years, several studies have showed that when RH is burnt, it generates between 17 – 20 % ashes, made up of about 87 – 93 % of silica 2-5 . Very few investigations have been conducted in Sri Lanka to extract silica from post-harvest residues 6,7 . Recent studies in Sri Lanka 8 on extraction of silica from post-harvest residues such as RH, Coconut husk and Rice straw have revealed that RH is more suitable than the other post-harvest residues to obtain industrial standard silica having particle size possibly in the range of nano scale. The objective of this study is to investigate the physical properties of extracted silica obtained from different varieties of RH found commonly in the western province of Sri Lanka. Proceedings of the Technical Sessions, 30 (2014) 105 -110 Institute of Physics – Sri Lanka