Preparation,Purification And Modification Of Rice Husk Ash With High Activity

This paper reviews the current domestic and international conditions of the preparation,purification and modification of rice husk ash.The rice husk ash was an ideal renewable resource that account for 20?30%weight of the rice husk,which was cheap and easy collection.Rice husk ashes were prepared by burning rice husk which have pozzolanic doping material with high activity and high specific surface area,and contains about 90%amorphous silica.Silica was an silica particles with ultra-fine and activity,and have excellent properties of porosity,high dispersity,light weight,chemical stability,high temperature,not burn and good electrical insulation,commonly known as "industrial gourmet powder".This paper were systrmatically studied from three aspects which containted the preparation of high activity rice husk ash,purification of white carbon black from rice husk ash and modification of rice-husk-silica.Rice husk ash which made from rice husk were prepared by pretreatment,burn,calcination,grinding.The effects of the preparation conditions on the performance of rice husk ash were main studied.The performances of the samples were characterized by XRD,BET method,laser particle size analyzer.The results showed that the preparation of activity rice husk ash should be carried with the temperature of 500 ?,calcination time was 4 h,the speed at 222 r/min star mill grinding 40 min,the specific surface area was 124.03 m2·g-1,the median particle size of the agglomerated particles was 9.30 ?m,and particle diameter of electron microscopy dispersed was 50 nm.The white carbon blacks and silicium gels were prepared by acid-alkali reaction method from rice husk ash.The effects of the pH values,reaction time,reaction temperature of the reaction system on the properties of white carbon blacks were main studied.The performances of the samples were characterized by the light color colorimeter,XRF and the volumetric method.The results showed that the purity of white carbon black reached 97.2%when the concentration of the sulfuric acid solution was 10%,the system pH value of 5-6,the reaction temperature was 85 ?,the reaction time was 2 h.Methyl triethoxysilane,hydroxyl silicone oil,amino silicone oil,n-octanol were used as modification agents.The super-hydrophobic silica film was prepared with sol-gel Synthesis,The modification mechanism was analyzed by infrared spectroscopy,SEM,static contact angle measuring instrument.The results showed that the four modifier all can be prepared super-hydrophobic silica film,the best experimental conditions were that:the amount of Methyl triethoxysilane was 5 ml,reaction temperature was 90 ? the reaction time was 8 h,the aging time was 36 h;the amount of hydroxyl silicone oil was 5 ml,reaction temperature was 90 ?,reaction time was 6 h,aging time was 36 h;the amount of silicone oil was 3 ml,reaction temperature was 90 ?,the reaction time was 8 h,aging time 36 h;the amount of n-octanol was 5 ml,reaction temperature was 50 ?,reaction time 6 h,the aging time of 24 h.The contact angle of SiO2 films was more than 150°.The mechanism of the modifier on SiO2 surfaces is a graft copolymerization,the hydrophobic groups in the modifier replace the hydroxy groups on SiO2 surfaces and make SiO2 surfaces present super-hydrophobicity.