ABSTRACT
Rice is one of the major crops grown throughout the world, it covers 1% of the earth's surface and is a primary source of food for billions of people Globally, approximately 600 million tons of rice paddy is produced each year. On average 20% of the rice paddy is husk, giving an annual total production of 120 million tons. In Egypt, the annual rice production is about 5,700,000 tons, equivalent to 200,000 tons of rice husk ash .After the separation of the rice from the paddy, one - third of the mass remains as a waste material ..Many workers have tried to use this agricultural waste to produce useful materials such as silica, zeolite, silica gel silicon carbide, activated carbon and sodium silicate notation coagulant aid. Rice husk ash is one of the most silica rich raw materials containing about 90-98% silica (this quantity depends on the soil type, plant variety and climatic conditions, geological factor, type of ground, near of harvest, sample preparation and analysis method..etc.The chemical process discussed below not only provides a solution for waste disposal but also recovers a valuable silica product, together with certain useful associate recoveries The activated silica or sodium silicate is one of the four basic types of coagulants aids beside pH adjusters, clay and polymers which increase a stability of coagulant and can unite with the positively charged aluminum or with iron flocs, resulting in a larger, denser lamellar floc that settles faster and enhances enmeshment.
The objectives of this study were to :produce rice husk ash (RHA) from rice husk, produce sodium silicate, and characterizations of new materials obtained by FTIR, XRD, and SEM. Under the study condition it was found that selected sample (optimum condition),of RHA which is designated as RHA5 obtained by calcination of untreated RH at 650 º C in semi closed system. FTIR shows signals at 1098 and 800 cm-1 for Si-O and O-Si-O respectively; XRD shows a sharp signal (amorphous silica ) at 2θ =22º and SEM examination indicate that rectangular particles should be distinguished. whereas RHA5 used in manufacturing of sodium silicate which is designated as Ssi5 and identified by XRD with its characteristic peak at 2θ about 28º, FTIR shows signals at (1443,994) for Si-O-Si, NFTIR shows signal at 7326 for overtone OH stretching Si-OH.