The Preparation And Performance Of Microporous Alumina Membranes

Due to their excellent advantages in thermal, chemical stability, the research and development on inorganic membranes have been an important part of novel membrane separations since they were successfully used in diary and beverage industry in France in the early 1980s.The aim of this research is to prepare microporous asymmetric ceramic membranes. The preparation process of diatomite substrate membranes by sintering method and asymmetric alumina membranes by the Sol-Gel technology as well as characterization methods about pore structure and gas permeability through membranes were mainly studied.The influences of particle size, the additives and their content in the slurry on the stability of diatomite slurry and formation of green supports were studied. The slurry with suitable viscosity, mobility, stability and good formation property and green supports with equal thickness and suitable strength was obtained. Under certain drying and sintering conditions, diatomite substrate membranes with porosity of 45% and average pore size of 0.16~0.42um were manufactured.The asymmetric A12O3 membranes were prepared by Sol-Gel technology with boehmite precipitation produced by the reaction of NaA102 and CO2 in Higee. The influence of the content and kind of peptizator on the transparent sol was investigated and the sols with suitable viscosity and good casting property were obtained. Binder was added to the sol before coating which was performed by casting. Non-crack asymmetric alumina membrane with several nanometers and porosity of 40% was obtained.The main parameters of ceramic membranes were determined. The porosity was measured by national standard (GB1966-80). The average pore size and pore size distribution of diatomite substrate membranes were determined by using a widelyemployed liquid displacement technique that is adopted from the ASTM F316-80. The average pore size of alumina membranes was determined by fluid hydrokinetic method.The permeation flux of different gases through different membranes was measured by experiments. The parameters of membrane tubes in dusty gas model were determined by fitting the permeation results of nitrogen. The theoretical values calculated through dusty gas model were coincided with the experimental results of oxygen and it was not the same case for carbon dioxide due to the possible surface diffusion.