Study On The Preparation And Separation Properties Of Novel PDMS Pervaporation Membranes

Pervaporation, as a novel liquid mixture separation technology, has outstandingtechnical advantages and promising application prospects in the removal of tracevolatile organic compounds (VOCs) from water. Preparation of membranes with bothhigh perm-selectivity and high permeation flux is vital to improve separationperformance of pervaporation process. For this purpose, it is necessary to investigatethe mass transfer behavior of the pervaporation process, to analyze the intrinsicrelationship between material characteristics and separation performance, and toestablish systemic theory for the selection and development of membranes.In this paper, a series of PDMS membranes filled with Calix[4]arene (CA),Calix[4]arene derivate (CAD) and Carbon Nanotube (CNT) respectively are prepared.The effects of filler type and filler content on the separation performance for thepervaporative removal of benzene from dilute aqueous solution are investigated. It isobserved that the addition of both CA and CAD can increase the separation factorsignificantly, but CNT can not serve this purpose. When 3wt% CA is added in PDMSmembrane, the separation factor is promoted from 3275 to 5604 and benzenepermeation flux decreases slightly.The structure morphology, the physical and chemical parameters of themembranes are obtained by FT-IR, DSC, XRD, DMA, PALS, PM, SEM, contactangle, swelling experiment. It is found that benzene flux is in inverse ratio withdegree of crystallization and in direct ratio with degree of swelling in feed solution.Bases on these results, a mathematical model is established to describe therelationship between benzene flux, degree of crystallization and degree of swelling.By the combination of the filling technology and composite membranepreparation methods, a novel composite membrane using CA filled PDMS as the thinactive layer and non-woven fabric as the support layer is developed. The separationfactor is promoted from 3275 to 5702 and benzene flux is promoted from 129 g/(m2·h)to 407 g/(m2·h).The effect of operation condition on the separation performance of thepervaporation is also investigated. There exists Arrhenius relationship betweencomponent flux and temperature and as the temperature increases component fluxincrease monotonously but separation factor decrease monotonously. Benzene fluxincreases linearly with the increase of benzene concentration and decreases linearlywith the increase of downstream pressure. Resistance-in-series is adopted to analyzethe variation of mass transfer resistance in boundary layer and in membrane with Re.The increase of Re can increase benzene flux of composite membranes but has littleeffect on benzene flux of homogenous membranes.