Study On The Preparation And Properties Of Mesoporous Silica Membrane

At the present time, the preparation of porous SiO2 membrane is an experimental work. There are many influencing factors and lack of regularity during this process .By this reason, the preparation technology of mesoporous SiO2 membrane by sol-gel was researched and the optimized technology of the preparation of SiO2 sol was obtained. TEOS was used for the source of silicon, ammonia is used for catalyst. It was found that the concentration of catalyst NH3 is the critical factor among various factors which influence the quality of SiO2 membrane, pH value and concentration of sol, template agents are the critical factors. Under suitable conditions, such as proper pH, sol-gel-dry process is self-adaptive, and it can adjust the speed of gel was weakened mostly so much so that was avoided.The pore size and pore size distribution of optimized experimental conditions were characterized through Liquid-liquid displacement method. The result showed that SiO2 membrane obtained from our experimental conditions had the maximum pore size 14.4nm, and its pore size distribution is from 8.8nm to 14.4nm. Determination of water flux under a given pressure showed that calcinating temperature had no obvious influence on the pore size of SiO2 membrane. In this work, self-adaptive sol-gel-dry process was implemented through control of pH value. Membrane pore and its distribution were controlled effectively by using certain template agent and temperature programming.The retention property of porous SiO2 membrane with mesoporous structure for rhodamine B aqueous solution was studied. When input concentration, operating pressure and pH value were changed, decolouration rate of rhodamine B solution was all above 95%, but removal rate of COD changed obviously. When the concentration was raised, removal rate of COD increased correspondingly; when the operating pressure was enlarged, removal rate of COD also increased correspondingly; pH value increase, removal rate of COD was below 20%.The preparation of mixed Al2O3-SiO2 membranes was researched preliminarily. A sol with a 1:1 molar ratio of Al2O3 to SiO2 has the shortest gelling time,it was about 15h.Higher mixing ratios produced longer gelling time. When pressure is 0.5MPa, and pH value is about 6.7, with mixed Al2O3-SiO2 membrane, the retention of Ca+ is 64.3%.