Preparation And Utilization Of Rice Husk Based Inorganic Materials

The preparation and application of rice husk based high surface area porous carbon as well as the preparation and application of nanometer silica provides the comprehensive utilization of rice husk as a whole feasible course.This dissertation includes the following main contents:1) taking rice husk as raw material, carbonate as activating agent to activate rice husk to produce high surface area porous carbon; 2) using waste water produced in the course of the preparation of porous carbon to extract silicon in rice husk and manufacture average diameter and well dispersed nanometer silica particle; 3) in-situ modification of the silica gel's surface in the procedure, alkyl growing on the inarch on the surface of silica becomes silica with superhydrophobicity by self assembly; 4) adsorbability of the porous carbon made from rice husk activated by alkali to metabolin in human body---- Creatinine, comparison with the adsorbability of commercial carbon in market, studies of porous carbon surface modification as well as heat treatment's influence on its adsorbability and exploration of the porous carbon's medical application; 5) by electrospinning technology, combining special wettability surface's manufacturing technique to produce polystyrene/silica composite film reinforced by silica and has superhydrophobicity property, and studying influence of electrospinning's producing conditions on morphology and wettability of compositive nanometer material.Taking rice husk as raw material, carbonate as activating agent for the preparation of high surface area porous carbon, it proves that the activating effect of K2CO3 obviously is much better than that of Na2CO3. The procedure is as follows. The ratio of K2CO3/C was 3(g/g). In order to activate the materials, they were kept at 800℃for 4 h in N2 atmosphere, and porous carbon with developed porosity will be obtained with BET specific area 1860 m2/g, pore size 2-3 nm and mesopore volume 0.49 cm3/g. By altering dose of activating agent and various activating process conditions, effective control of porous carbon's specific surface area and pore distribution will be achieved, which paves the way for further development and utilization of rice husk. It becomes a tendency to prepare high surface area porous carbon with developed pore structure from activating rice husk by hydrate instead of carbonate. This essay, at the same time, has studied the activating agent's influence on porous carbon's BET surface, pore structure and pore diameter; and adopting TGA plot to monitor the change of substances'weight during reaction process. Meanwhile, it has proposed a more reasonable explanation of mechanism of activation. This essay has compared a series of rice husk based porous carbons'adsorbability of metabolin in human body---- Creatinine with that of commercial carbon. RHC's adsorption capacity of CR is much larger than commercial carbon's, thus the application prospect of porous carbon from rice husk activated by alkali is very promising in absorbing toxin in human body. RHC's adsorption capacity of Creatinine increases with temperature; as it rises from 25℃to 80℃, Creatinine will become two fold or more; porous carbon's adsorption capacity becomes strongest when adsorption system is neutral; when concentration of added NaCl is below 0.5 M, porous carbon's adsorption capacity decreases with increase in concentration of sodium chloride. As the concentration of NaCl exceeds 0.5 M, porous carbon's adsorption capacity of CR increases along with the increase of ion concentration. Under same conditions, porous carbon's adsorption capacity is influenced by pore structure and surface properties. The pore structure of porous carbon is one of the major factors that influence its adsorption capacity. Though commercial carbon has higher mesopore volume and larger pore diameter, its adsorption capacity is clearly lower than that of RHC's, because porous carbon's adsorption is micropore adsorption and the number of micropores determines porous carbon's adsorption capacity. The reaction of preparing porous carbon from rice husk activated by NaOH becomes acute with increase of time and temperature, forming a great deal of micropores. Surface modification enhanced porous carbon's adsorption capacity of CR, but heat treatment evidently decreases porous carbon's adsorption capacity of CR. The adsorption capacity of porous carbon after surface modification is stronger than that of porous carbon without any modification. Porous carbon modified by hydrochloric acid has the strongest adsorption capacity of CR. Porous carbon modified by strong oxidizability acid--- nitric acid has the weakest adsorption capacity of CR. Porous carbon modified by less strong oxidizability acid--- hydrogen peroxide has medium adsorption capacity of CR. Heat treatment obviously causes changes of porous carbon's pore structure, mesopore volume increased, average pore diameter enlarged and micropore volume decreased. The increase of mesopore volume and enlargement of average pore diameter are influenced by the removal of surface functional groups and collapse of micropore in high temperature. The decrease of micropore obviously makes the adsorption capacity of heat treatment sample much weaker than primary sample or surface modified porous carbon.Taking rice husk as raw material and using sol—gel method, it could successfully prepare mono-disperse silica particles in about 60 nm diameter at room temperature. This simple and economic method has widened rice husk's application range. At the same time, debasing reaction was carried out at lower temperature in a mild system to modify silica that is modified from rice husk by hexadecanol in situ and to prepare superhydrophobic silica particles. Surface wettability of inorgic materials can also be controlled by alkyl's length. This simple experimental method can be further extended to other inorganic material's surface modification. In this essay, a simple treatment has been made to fume silica, and prepare polystyrene/silica composite film by adopting electrostaticspinning method. The filling of silica enhance polystyrene's hardness; at the same time, through the change of polymer's concentration and silica addition, we could modulate the composite film's surface wettability and morphology, and to complete the controlling of film's wettability. This preparation method can be widely used in other addition of inorganic particle and polymer, and can make functionalization design of polymer's performance. This method is low cost and employed in mass production. It is a method with application prospects.In conclusion, through the preparation of high surface area porous carbon, the development of porous carbon performance and nanometer silica, this essay provides the comprehensive application with a brand new program. It has not only made achievement in basic fields but also provided the comprehensive application of rice husk through a new utilizing approach, with the theoretical analysis and practical application and important social and economic meaning.