| With the rapid development of global industrialization, the consumption of primary energy is increasing, which causes energy depletion and environmental pollution problems and the negative impact of these problems are increasing. For its own survival and development, the human is constantly looking for new energy sources to reduce or substitute one-time energy consumption. In a variety of renewable energy, biomass, which is the only renewable carbon source to store solar energy, is an important renewable energy component. The research of heat energy utilization of rice husk has become an important direction to develop new energy sources. In the current, biomass is mainly used for heating, power generation and synthetic chemical industry. Large-scale promotion of the use of rice husk to generate power is now a new technology, which is spread by our country. Besides of use of rice husk burning calories, the use of combustion ash and gases is also an important issue.Rice husk is a by-product after processing. According to statistics, China's annual output of more than 60 million tons of rice husk. The use of rice husk to generate power is not only solving the pollution problem, but also developing energy resources, which plays a huge role to develop our national economy. However, the burning of rice husk to generate power produces large amounts of rice husk ash, if not dealt in time, which remains an environment problem. Because rice hull ash contains large amounts of unburned carbon, it is an excellent raw material for preparation of activated carbon. Moreover, rice husk contains 16% -20%of amorphous hydrated silicon dioxide, and the main component is silicon dioxide after the combustion of rice husk, besides, small amounts of other mineral impurities, which indicates that it is an ideal raw material to produce fine chemical product-white silica. In this paper, silica was leached from RHA as sodium silicate by NaOH treatment and industrial waste gas CO2 was used as precipitator. The silica extraction yield reached 99 wt.% and the effect of parameters, which involved the concentration of NaOH, the extraction time and impregnation ratio, on the silica extraction yield was investigated in this study. The optimum extracted conditions of silica from rice husk ash are as follows:the concentration of NaOH is 4 wt.%, the extraction time is 2.5h and impregnation ratio is 9:1. The extracted yield of silica is up to 99 wt.%. Furthermore, the extraction reagent NaOH could be regenerated by the addition of calcium hydroxide (Ca(OH)2) slurry into the filtrate after carbonation, and calcium carbonate (CaCO3) by-product with high purity was obtained. The X-ray diffraction patterns (XRD) indicated the amorphous structure of the silica powders and Fourier transform-infrared spectroscopy (FTIR) indicated that the product is hydrated silica. The average diameter of silica particle is around 40nm and the silica product has a well dispersion and fine purity. At last, Preparation and carbonization mechanism of nano-silica was studied.Then, the traditional method of Na2CO3 fused silica sand was changed in the second chapter. Na2CO3 was used to extract silica from rice husk ash, the resulting filtrate was then reacted with CO2 to prepare good dispersant nano-silica. The parameter of affecting on the silica extracted yield, such as Na2CO3 concentration, extraction time, carbonization time, and the impregnation ratio were studied. Na2CO3 acts as a catalyst in the extraction process, and only a small amount if it was lost during the reaction, thus, the recycling of extractant Na2CO3 was achieved through the timely supplement of it, and the reaction mechanism was discussed. This method reduced the cost of industrial waste water and predigested the traditional craft, therefore, the above method is a green and sustainable technology. The remained carbon content in the ash residue has been greatly improved after alkali extraction, and some is even as high as 90% or more, and become porous and loosen, thus it is a good material for preparation of activated carbon. In the silica leaching process, due to alkali etching effect of rice husk ash, the resulting ash residue was generated a lot of gaps. If some further activation was done, active agent can enter the ash residue internal to the full etching of carbon, and further increase the number of holes, therefore, better activated effect was achieved. In this chapter, a strong base KOH was used as activated agent to react with ash residue, the effect of parameters, which involved activated temperature, impregnation ratio, and activated time on pore volume, BET surface area and iodine adsorption capacity of activated carbonwas discussed in this study. The activated carbons are found to be a mixture of micropore and mesopore pore structures. The maximum pore volume, BET surface area and iodine adsorption capacity of as-prepared active carbon can reach 1.22 cm3/g,1936.62 m2/g and 1259.06 mg/g, respectively. Field emission scanning electron microscopy (SEM) was used to characterize the morphological features of the ash after step by step treatment, and we found that high temperature is a necessary condition for making pore.Because of their high melting point, high stability, non-toxic, and other special properties, hollow silica microspheres have got the majority of public concern. Template method is a familiar method in the preparation of the application of special shape materials. With this method, a particular material was used as the morphology of aids-templates firstly, and then some materials were needed to be covered or filled in the template to get the required shape. Several researchers used a small number of acid-soluble inorganic salt or oxide as the core, but the majority used polymer template as the core, besides TEOS was usually used as a silica source. Silica source used in this paper was from the second chapter, which was filtrate obtained from dealing with rice husk ash by sodium hydroxide, and PVP and CTAB were used as the co-templates, besides, sulfuric acid was used as precipitng agent to synthesize hollow silica spheres. After calcination at high temperatures, a hollow silica microspheres structure was obtained. The formation mechanism of silica hollow microspheres was raised through the design of experiments and characterization of product. Moreover, we found the key parameter to get silica hollow spheres was the ratio of PVP and CTAB.Finally, the precipitated nano-silica product was modified by fatty alcohol. Different levels of silica surface modification were achieved through the use of different chain length of fatty alcohol. By contact angle test, we found that when a certain amount of alcohol was used, the contact angle of the final product increased with the growth of chain length of fatty alcohol increasing, and the mechanism of this phenomenon was discussed. Finally, the modified nano-silica product was added into the polymer, and we confirmed that after modification of the silica, a good compatibility with organic substrate was achieved through SEM cross section analysis. Thus a good dispersion of inorganic particles in the polymer material was got through this method.In summary, the silica was extracted from rice husk ash by alkali, and nano-silica powder was prepared by carbonation method. Besides, the ash residue after alkali extraction was activated by KOH to obtain the activated carbon with high specific surface area and strong adsorption. The method in this paper makes full use of the two components of rice husk ash, which provides a new solution for the comprehensive utilization of rice husk ash. It is not only fruitful in the basic fields, but also on the combined the practical application with the theoretical analysis, Which has the important social significance and economic significance.
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