Research On Coupled Field Pervaporation Process

Pervaporation technology is a new type of membrane separation technology.Because of the advantages of high efficiency,energy saving,simple process and easy operation,it is widely used in the organic dewatering,organic matter-organic separation and so on.The traditional pervaporation process follows the dissolution and diffusion mechanism,and the mass transfer rate of the permeate is controlled only by the different vapor pressure across the membrane.In this paper,the coupling field pervaporation model is established by introducing an asymmetric electrostatic field in the traditional mode Process,so that mass transfer process has been greatly improved.In this paper,we discussed the effect of asymmetric electrostatic field on the mass transfer of permeate with different polarity,the effect of different directions of gradient field on mass transfer and the effect of electric field on membrane structure parameters is also discussed.In this paper,a commercial PVA membrane was used as a pervaporation membrane for the coupling field pervaporation of water,ethanol,propanol,isopropanol,butanol,isobutanol,ethyl acetate,m-xylene and p-xylene.The effects of electric field on different substances were discussed from the perspectives of ethnol-water.organic matter of different systems,homologues and isomers.The results show that,Under the forward gradient field,the flux and the increasing rate of the polar matter are proportional to the gradient of the electric field,and the extent of the change is related to the species of the permeate.The flux of the non-polar substance is not affected by the electric field;for the water and the organic matter,The effect of the electric field on the water is greater than that of the ester,and the effect of the electric field is larger when the molecular weight is smaller in the homologues.At the same time,It is also possible to improve the separation performance by increasing the flux of some isomers by introducing an electric field.The influence of the gradient field on the direction of the electric field is also discussed.It is concluded that the forward gradient field has a positive effect on the mass transfer process of the polar substance,while the reverse gradient field has a diversion effect,but in both cases,The degree of impact is the same.The elements and micro structures of the membrane surface were characterized in these paper.The results show that there are no changes in surface structure and cross-sectional morphology of the membrane after appiying electric filed.The water contact angle and chemical bond of the membrane surface,as well as the element and element contents of the membrane surface have no changes too.