Modified Rice Husk Ash And Its Application In Organic Wastewater Treatment

Rice husk is one of by-products of rice processing. After being incinerated by power plant, it generates rice husk ash(RHA). Rice husk ash possesses high specific surface areas and pole with high silicon content. The objective of this work was to research the application of modified rice husk ash used in the adsorption of organic wastewater. Meanwhile, the sodium silicate generated during rice husk ash modification was used to prepare mesoporous silicas materials. Waste multi-using was achieved in the whole processes, and treating waste with waste got good effects.The structures of RHA, RHA by hydrofluoric acid treatment(RHA/HF) and RHA by sodium hydroxide treatment(RHA/NaOH) were characterized, and their constituents were analyzed. The results demonstrated that peak of silicon dioxide disappeared after the RHA was treated by hydrofluoric acid, and peak of silicon dioxide became weaker after the RHA was treated by sodium hydroxide, but peak of carbon was no obvious changes. Both of specific surface area and pore volume of RHA increased, and RHA/HF had largest specific surface area and pore volume. When RHA was used as absorbent to adsorb methylene blue, in order to achieve best adsorption, the initial concentration of methylene blue was 80mg/L, pH was adjusted as 8, temperature was set as 15℃, rotating speed was 110r/min, the dosage of RHA was 15g/L, adsorption time was 85 min. When modified RHA was used as absorbent to adsorb methylene blue, in order to achieve best adsorption, the initial concentration of methylene blue was 130mg/L, pH was adjusted as 8, temperature was set as 15℃, rotating speed was 90r/min, the dosage of RHA was 15g/L, adsorption time was 120 min. The adsorption isotherm was discussed by changing the initial concentration of methylene blue. The result demonstrated that adsorption of methylene blue in both of RHA and RHA/HF followed the Langmuir isothermal adsorption equation, and the adsorption belonged to monolayer adsorption. Meanwhile, adsorption kinetics of methylene blue adsorption was discussed by changing adsorption time. And adsorption of methylene blue followed the pseudo-first order kinetic equation. By comparing methylene blue adsorption results of three materials, RHA/HF was proved to be easier to adsorpt methylene blue with best adsorption results, and the specific surface area of RHA/HF was largest.Meanwhile, adsorptions of phenol in water by mesoporous RHMCM-41 and CH3-MCM-41 were also researched in our work. The effect of adsorption time, temperature and other factors had been investigated when mesoporous silicas materials were used to adsorb phenol. Adsorption kinetics, adsorption isotherm and adsorption thermodynamics were researched. And adsorption mechanism was preliminary discussed. In equilibrium adsorption capacity, the phenol adsorption capability of CH3-MCM-41 was improved compared with RHMCM-41. Adsorption stability of modified materials was highly improved. And adsorptions of phenol by RHMCM-41 and CH3-MCM-41 followed pseudo-second-order kinetics. Freundlich isotherm can be well applied to fit the adsorptions of phenol by these two materials.