Research Of Preparation Of Silica From Rice Husk Ash

China is a major rice producing country, the rice husk yield is about more than a third of that of the world, and less than 10% as a primary fuel use. This is a tremendous waste of resources, and has caused great environmental pollution. As to improve economic benefit, utilize resources and protect environment, the preparation of silica from rice husk ash in this research is of great importance for the utilizing of rice husk ash.Firstly, the study determined the method of detection method of silica purity, and then the optimum conditions of preparation of silica from Rice Husk Ash were researched, and also did the main factors that effected the quality of product, and the washing conditions by ultra sonic were also studied. Lastly, product was analyzed and characterized by Whiteness Meter, IR, SEM and XRD methods.During the process of the determination of detection method of silica purity, the optimum conditions of chromogenic of silicomolybclenum yellow method and silcomolybclenum blue method were determined, and the detection methods were established, and the silicomolybclenum yellow method was chosen to determine the purity of silica by comparing the results of repetition experiment, recovery experiment and the evaluation of the accuracy.During the research of the processes of preparing silica from Rice Husk Ash, the module of water glass and the dissolution rate of silica were taken for indexes, The reasonable conditions of preparation of the water glass were determined on the basis of the single factor experiments and the actual needs of modulus: the stirring speed was 250r/min, reaction time was 2.5h, solid-liquid ratio was 15g:100mL, alkali concentration was 1.5mol/L. Then the process of preparation of silica from water glass was researched, the module and concentration of water glass , terminal pH of reaction, reaction temperature, the concentration and the addition speed of sulphuric acid , the amount of chelating agent, aging time were found to have effects to the quality of silica, the purity of silica was taken for index , the reasonable conditions of preparation of silica were determined On the basis of the single factor experiments and analysised by RSM: the module of water glass was 2.3, the concentration of water glass was 9.7%, reaction temperature was 80℃, terminal pH of reaction was 9.5, the amount of chelating agent was 0.8%, the concentration of sulphuric acid was 10%, the addition speed of sulphuric acid was 0.214 mL/(min?100g), aging time was 1.5h. Then the washing condition by ultra sonic was researched, The pulse cycle of ultra sonic, the concentration of silica particle, ultrasonic power and the treating time were studied, the reasonable conditions of washing by ultrasonic were determined on the basis of the single factor experiments and analysised by orthogonal test: the pulse cycle of ultra sonic was 4s, the concentration of silica particle was 0.05g/mL, ultrasonic power was 900w, the treating time was 15min, and the purity of silica prepared under the optimum conditions was 98.4%. The prepared silica is completely consistent with the national standard, the IR analysis shows that the presence of adsorbed water, silanol hydroxyl groups and silica, the analysis of XRD shows that prepared silica is amorphous substance ,under SEM, the silica powder is consist of aggregates, and the particle size of the particle is 250nm.