Preparation Of Bio-based Silica Microsperes And Actived Carbons Directly Utilizing Rice Husks

China is the largest countries of rice growing in the world, generates one of the major wastes of the world, namely, rice husks (RHs). Approximately3.86×107of RH is produced in2008year, but most of it is not utilized because of its poor protein and high ash content. Rice husks are usually used as a low-value energy resource, burned in the field, or discarded, which are unfavorable to environment. Therefore, the rational utilization of rice hull is signality. In this paper, a simple method to the preparation of SiO2microspheres and high specific surface area activated carbon from rice husks (RH) was developed, and two materials were investigated by some methods.The main research work is as follow:1. The rice husks were extracted with2M NaOH solution to obtain a extract contained silica and lignin, and silica spheres were obtained after addition of distilled water, ethanol, H2SO4and PEG to the extract in a controllable sol-gel process and calcination at550℃. The SiO2microspheres produced under these conditions exhibited a relatively uniform particle size distribution as determined by LPSA and SEM, which indicated a cooperative function of added PEG and extracted lignin towards the formation of SiO2microspheres.2. Prepare activated carbons with mesoporosity using the residues of NaOH-pretreated RHs. The influences of activation temperature and activation time on the surface area, pore volume and pore radius of activated carbon were investigated based on nitrogen adsorption/desorption isotherms and transmission electron microscopy (TEM).3. The adsorptive behavior of mesostructured activated carbons obtained under optimum preparation conditions was evaluated using methylene blue (MB) as model adsorbate; kinetic character and adsorption isotherm were studied in details by pseudo first-order model and pseudo second-order model, Langmuir and Freundlich models, respectively. It was demonstrated that the pseudo second-order model and Langmuir isotherm well fitted to the adsorption characteristics of as-prepared activated carbons with mesoporosities. Moreover, thermodynamic data on the adsorption process were also outlined to illuminate the adsorption thermo-chemistry between activated carbons, produced from NaOH-pretreated RHs, and MB molecules.