| Pervaporation is a kind of green and high efficient membrane separation technology and its application field is more and more wide. It has a good application prospect in the field of dehydration of organic solvents, recovery of valuable organic compound and separation of organic compound. However, the well-known permeability/selectivity trade-off of polymeric membranes usually leads to a separation upper-bound with current generation of membranes. Therefore, to develop membrane systems with improved separation performance has become a subject of study with extensive efforts in the field of pervaporation.In this paper,a commercial polyvinyl alcohol membrane was employed to separate binary mixtures by pervaporation,an asymmetic electric field was placed across the membrane to make the electric field intensity in the permeate side is greater than the feed side,establishing an asymmetric electrostatic field coupled pervaporation process.Migration of polar molecules under the electric gradient force, leading to the increase of permeation flux and separation factor which was associated with the polar difference of the binary components.89.4 mol% ethanol/water azeotrope was used as feed solution, voltage gradient and temperature were investigated to envaluate the separation performance of pervaporation process. Mass transfer model of the coupling field were established. Results show that under the same experimental conditions, addition of an asymmetric electric field increased permeation flux and separation factor. Permeation flux was increased by 37.7% at 4kV where vacuum pressure is 90 kPa, electrode distance is 23.5 mm, needle electrode is positive, plate electrodes connecting the ground.The asymmetry electric field coupling pervaporation process were used in the dehydration of isopiopyl alcohol, ethylene glycol and ethyl acetate.The results show that the asymmetric electric field can improve the permea-tion flux and separation performance at the same time.
|
PDF Full Text Request