Study On Modification Of Polyimide Nanofiltration Membrane

As a new membrane separation process, nanofiltration has achieved rapid development in the last 20 years. With the applications of nanofiltration membranes broad increasingly, the objects handled by nanofiltration become more and more complex. A single membrane material has been unable to meet the request of practical application of different molecular weight cut-off (MWCO), chemical stability, mechanical strength and resistance to pollution, and the need for comprehensive performance. Therefore people have made a lot of research work about modification of membrane materials and membrane surface modification, so that the performance of nanofiltration membranes could be improved to meet the needs of practical application better.The conditions of UV-modification are mild, and the equipment is simple, so that UV-modification is more suitable for surface modification of polymer membrane. Polymer membrane surface may occur grafting reaction by the UV-irradiation, so that the properties of membrane surface could change a lot. In this paper, butyl acrylate was selected as the grafting modification monomer of polyimide nanofiltration membrane among methyl acrylate, methyl methacrylate and butyl acrylate, which was the best lipophilic monomer. The impact of UV irradiation time, graft monomer concentration, and ultraviolet irradiation distance on the grafted effect of polyimide nanofiltration membranes were investigated by single factor experiment. The results showed that the grafting yield increased with the UV-illumination time increasing, and decreased with the increasing ultraviolet irradiation distance, and increased first and then decreased with the increasing of the concentration of grafted monomer, the grafting yield reached the maximum when the monomer concentration was 15%. The modified polyimide nanofiltration membranes for lubricant retention rate significantly increased than non-modified polyimide nanofiltration membranes. The retention rate could be increased from 66.5% to 93.1% corresponding with the retention rate increasing, the membrane flux decreased.By ATR-FTIR analysis and SEM analysis before and after modification of polyimide nanofiltration membranes, the results proved that butyl acrylate was grafted onto polyimide nanofiltration membrane really.