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Abstract
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Extensive application of silica nanoparticles in various industrial products has led to that it considered as one of the strategic products. Rice husk is an agricultural waste with a high content of amorphous silica. However, existence of metal ion impurities and unburned carbon in the rice husk content could have an adverse effect on product color and purity. In a first stage, the purpose of the present study is optimization of silica extraction and improvement of its purity and eventually production of high quality silica nanoparticles. In this regard, nitric, sulfuric and hydrochloric acids applied for consideration of performance of three different rice husk pretreatments. Silica extraction process carried out by controllable calcination methods in an electric furnace by 600 ?C. The results of XRF analysis reviled that hydrochloric acid treatments have highest performance than the other treatments, and the purity of the obtained silica by this method was 95.55%. The major impurities of obtained silica were K2O, CaO and P2O5 that considerable portion of them removed by an acid treatment. In addition, the results of XRD analysis revealed that the extracted silica is amorphous. In the second stage of the present study, silica nanoparticles produced using chemical precipitation. The BET results show that the specific surface area was 409.69 m2/g. The result of SEM analysis shows that the average of the particle sizes is 200±20 nm.
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