| Through study the characters of organic membrane material, a kind of nanofiltration membrane with good performance was obtained, and then a new kind of hybrid nanofiltration membrane with the merits of organic material and inorganic materials. On the basis of further study, a kind of nanofiltration membrane having good separation performance was prepared. With chitosan as the membrane-forming material, and through investigations into the effects of main factors influencing the performance of chitosan nanofiltration membrane during the processes of making membrane, the most rational conditions of making membrane was confirmed. These main factors are solvent, concentration of chitosan, content of cross-lining agent, temperature, heating mode, time, species and content of addition agent, coagulation mode and etc. For improving the separation performance of nanofiltration membrane, with chitosan as the material of organic membrane, this thesis prepared chitosan/SiO2 hybrid membrane by phase inversion process and then systematically analyzed the main structure and performance influencing factors, such as solvent, concentration of chitosan, content of cross-linking agent, temperature, heating mode, time, content of addition agent, content of SiO2 and etc. Final productions were characterized in terms of thermal stability, chemical stability, intensity and etc, and microcosmic structure was observed with stereoscan; water flux determined with Quadi-Dynamic instrument, interception rates of monmvalent ion and divalent ion were studied.The study indicated that the tensile strength of chitosan membrane is better than chitosan/glutaric dialdehyde mixed membrane, but water flux of chitosan membrane is too small to have a promising future. Although the tensile strength of chitosan/glutaric dialdehyde mixed membrane felled down, the water flux had a big improvement. When mixed with nano-scale SiO2, the mechanical character and tensile strength of chitosan/glutaric dialdehyde mixed membrane were intensified greatly, and its degree of swelling was obviously improved and water-percolation rate was advanced to a certain extent. When glutaric dialdehyde was mixed into the SiO2/chitosan mixed membrane, a excellent nanofiltration membrane can be obtained with some good characters, such as water-percolation rate, thermal stability, chemical stability, mechanical intensity and etc.The results of experiments indicated that the nanofiltration membrane with excellent performances could be obtained when volume fraction of acetic acid was 4%, concentration of chitosan was 28 g·L(-1), content of glutaric dialdehyde was 0.2%, content of SiO2 was 3.4%, content of polyethylene was 8% and desiccation temperature was 40°C, of which water flux was 40L·m-2·h(-1), interception rate to divalent ion reached to 60%. This kind of membrane has good thermal stability, chemical stability and mechanical intensity.Use the SiO2 and the chitosan to make Nanofiltration membrane. |
