ABSRACT
Rice husk is a form of agricultural biomass that provides an abundant silicon source. Rice husks are widely burnt in agricultural fields in Nigeria especially in Abakilike, Nasarrawa, Gombe and Ekite state because it is difficult to find other uses for them. Farmer’s burn rice hulls usually under incomplete combustion conditions to avoid accidental fires. The objective of this study was to assess the extraction of silica from rice ash, to develop a process for production of low cost silica from rice hull (husk) and to identify the purity of the produced silica at the optimal condition. Alkaline, acid leaching was the method adopted for this research.
Initially received from Rice husk was properly washed with hot water to remove contaminants of water-soluble organic matters present. Next, it was mixed with hot 1.0M of Citric Acid solution .This was done to hydrolyze the carbonaceous materials; (such as cellulose, hemicelluloses, and lignin) and also to remove the elemental metals and the metallic oxide which influences the purity, structure and color of the silica. Next, The Pretreatment sample was then mixed in a 2.0M Hydrogen Peroxide solution which is used for purifying the husk. This was designated as pretested Rice Husks before it was further calcined at 5000C, 555.650C, 6900C and 824.350C for 3 hrs 15minutes to remove the volatiles in the sample and determine the amorphous structure of SiO2. Next, the thermally treated RHA was mixed with alkali solution to produce sodium silicate solution and precipitated silica was produced by the neutralization of sodium silicate solution.
Rice Husks soaked in nitric acid produced the maximum amount of the sodium silicate solution and precipitated silica. Sodium oxide (Na2O) content and silica (SiO2) content in the sodium silicate solution were also determined. Extracted precipitated silica particles were characterized with X-Ray fluorescence (XRF) Spectrometer. Which determine the atomic and molecular structure of the amorphous silica crystal by measuring the angles and intensities of diffracted beam of the rays .The purity of silica was analyzed in the following order, fit summary, the designed model ANOVA ,fit statistic, diagnostics, and model graph, which was basically shown by contours plots and Response Surface 3D plot, Normal plot of residuals and General summary of the report which comprises of run order, Actual value and predicted value using Respond surface methodology RSM package.
This economic technology as applied to waste material also provides many benefits to the local agro industry. Thus this Research may be providing a low cost and simple method to prepare functional materials.
