Study On Fabrication Of Homoporous Composite Membranes By Breath Figure And Thermal Adhesion Method

Homoporous membranes can be used for high high-resolution separation without reducing permeation,therefore are important in membrane separation process.Among the studies about the preparation of homoporous membranes,the breath figure method(BFM)attracts more and more attention because of convenience,cheap and wide choices for membrane materials.However,the homoporous membranes prepared by BFM usually are lack of mechanical strength for separation.It's worth noting that although some methods have been reported to solve the problem,they often have much restriction in membrane materials.This is why the homoporous membrane can't be used widely in separation process.All in all,how to easily and cheaply improve their mechanical strength is very important.This work aims at combining BFM and thermal adhesion method to improve mechanical strength.Four usually used membrane materials i.e.,PSF,PES,PPO and PEI,were proposed to fabricate the reinforced homoporous membranes and the relevant membrane separation process i.e.,size-sieving filtration and membrane distillation were analyzed and studied.First,the PSF homoporous membrane was prepared by BFM and the influence factors i.e.,casting solutions with various acetone concentrations,casting solutions concentration and substrates were researched thoroughly.The optical and SEM images indicated that the PSF homoporous membrane has sharp pore size distribution when the casting solutions concentration was 2.0 wt.%and acetone concentrations was 3.0 wt.%.The EDX analysis showed the homoporous layer is tightly adhered on substrate.The novel method for fabricating the reinforced homoporous membranes was introduced successfully.The particle sieving experiment indicated that it can separate particles precisely.The water permeation and regeneration tests indicate that its performance is better than commercial microfiltration membranes.Based on the novel method,PES,PPO and PEI reinforced homoporous membranes were also fabricated successfully.This means that the novel method has good upscalability.Then,the reinforced PPO homoporous membrane was applied to membrane distillation process.The work also studied influence factors i.e.,casting solutions amount and moist nitrogen with various flow rate were carried.Finally,the SEM images manifested that the pore size of the homoporous membrane can be reduced from 2.73?m to 1.55?m when casting solutions amount was 1500?L and the moist nitrogen flow rate was 3.5 L/min.At the meantime,PDMS solution was coated onto the membrane in order to optimize its performance for membrane distillation.The SEM images and EDX analysis showed that the membrane pore size was reduced into 0.8?m and the water contact angle was enchanced from 115.4 ~o to130.0 ~o when the PDMS solution concentration is 5.0 wt.%.Based on analysis about membrane distillation,we found that the reinforced PPO homoporous membrane with PDMS layer exhibited lower thermal conductivity,better ability to mass transfer and antifouling than the commercial membrane.