The Comprehensive Utilization Of Rice Husk

Husk of rice is the main by-product, accounting for about20%of rice weight. Majorcomponents of post-combustion of rice husk are silica, and few other mineral impuritiescontent. It is the production of fine chemical products ideal silica materials. According tostatistics, more than30million tons annual output of rice husk, are still increasing. Rice huskas the main by-products are mostly processed as waste, inadequate as a primary fuel use, thisis not only a waste of resources, the environment, causing major pollution and thecomprehensive utilization of rice husk has been the subject of one of the people to study. Thiscan not only make full use of rice husk that agricultural waste, reduce environmentalpollution, but also have an important value of development, become a new renewableresource. This thesis focuses on the reuse of rice husk to do the following research:1.The silica and activated carbon was prepared by the carbonization-alkali dissolvingmethod using the rice husk as the raw material, and discussed the effect of preparationcondition on the product in this paper. The results indicated that the temperature and time ofcarbonization are600℃and30min, the time of alkalization is4h, the concentration ofsodium hydroxide is2.5mol/L. The silica dioxide extracted from the rice husk was amorphous.The yield, purity and whiteness of silica are90,93.5and95%, respectively. The methyleneblue adsorption capacity of activated carbon is24ml/0.1g.2.The project researched a method of silica preparation from Rice Husk directly withoutproducing water glass as intermediate product，by pretreatment of acid activation.Researchthe conditions of silica preparation （including the activation of type of acid,acid activationtime and temperature, calcinations’ temperature and time）:3%sulfuric acid, boiling time of4h, calcinations’ temperature of600℃, calcined3hours. Under these conditions the productobtained in the brightness above95%.3. P-type zeolite was synthesized by carbonization, alkali-dissolving and hydrothermalmethod，using the rice husk and aluminum hydroxide as the starting materials. It was foundthat the optimal zeolitization condition is: temperature85; time8h; SiO₂/Al₂O₃molar ratio of 4.0; Na₂O/SiO₂molar ratio of1.43and H₂O/Na₂O weight ratio of18.3.The prepared productshows that the calcium ionic exchange capacity of330mgCaCO₃/g. XRD and SEM of theproducts show that pure form, single phase and high crystalline zeolite P samples weresynthesized under optimum condition.4.Zeolite P was synthesized by carbonization, alkali-dissolving and hydrothermal methodusing the rice husk and aluminum hydroxide as the starting materials. The composition andprocess parameters for the synthesis of zeolite P have been optimized. It is found thatSiO₂/Al₂O₃molar ratio of5.6, Na₂O/SiO₂molar ratio of1.43, and H₂O/Na₂O molar ratio of18.3give maximum calcium ionic exchange capacity of320mgCaCO₃/g at the crystallizationtemperature of85℃and reaction time of24h. XRD and SEM of the products show that pureform, single phase and high crystalline zeolite P samples were synthesized under optimumcondition.The result show that: high purity and activity silica activated carbon and high crystallinezeolite were prepared from rice husk. Expecially the Products P zeolite showed much betterProperties than those reported referenees（the calcium ionic exchange capacity of280mgCaCO₃/g）. This study provides a new method for the comprehensive utilization of ricehusk.