Preparation Of PES Hollow Fiber Membranes And Separation To Organic Pollutants From Water By Pervaporation

Pervaporation is an effective and economic membrane separation method for the separation of trace components in mixture.In recent years,the method of pervaporation membrane separation is paid more attention than other membrane techniques for the treatment of organic pollutants in contaminated water.The method has unique advantages in the treatment of low-concentration organic wastewater,especially for volatile organic compounds (VOCs),such as 1,2-dichloroethane,benzene,trichloroethylene,chlorobenzene,1,1,2,2-tetrachloroethane and toluene.In this dissertation,polyethersulfone(PES) was used as the main membrane material to prepare hollow fiber pervaporation membrane.In addition,polyethersulfone-Polyimide(PES-PI) and Polyethersulfone-Polyetherimide(PES-PEI) blend hollow fiber pervaporation membranes were also prepared.The pervaporation performances of the membranes were researched by separating VOCs from aqueous solutions.The effects of spinning condition for the preparation of hollow fibers(such as coagulation temperature and air gap distance) and operating conditions(such as temperature,concentration and velocity of feed liquids) on the PV performances of the hollow fiber membranes were investigated.The experimental results show that:for PES hollow fibers,the separation factor decreased but the flux increased with the increase of the VOCs concentration in the feeds;When the temperature of the feeds increased,the permeation flux increased but the separation factor decreased,and the influence of temperature on flux can be explained with Arrhenius equation; With the increase of the velocity of the feeds,both the separation factor and the permeation flux increased.For the PES-PI blend membranes,when the weight fraction of PI was 41 wt.%,the air gap was 7cm and the temperature of coagulation was 45℃,the PV performance of prepared membrane was the best.The effects of operating condition on the performances of PES-PI membrane were similar to those of PES membrane;for the PES-PEI blend membranes,when the weight fraction of PEI was 30 wt.%,the PV performance of PES-PEI membrane was the best.The effects of spinning condition and operating condition on the performance of PES-PEI membrane were similar to those of PES-PI membranes.The pervaporation performances of PES-PI and PES-PEI blend hollow fiber membranes were strongly related to the molecular size of the VOCs.The order of the selectivity was reverse to that of the molecular size of the VOCs.For the PES-PEI blend hollow fiber membrane prepared at the conditions when the air gap was 7cm and the temperature of coagulation bath was 45℃,it possessed high selectivity to the aqueous solutions containing 0.04 wt.%of VOCs at 20℃.The separation factors to 1,2-dichloroethane,benzene, trichloroethylene,chlorobenzene,1,1,2,2-tetrachloroethane and toluene were 7070,5923, 5759,3952,3511 and 3205,respectively,which were better than those reported in the literatures.The results show that PES-PEI blend hollow fiber membrane has prospect for industrialization in the treatment of organic pollutants in contaminated water.