Study On Preparation And Properties Of Pervaporation Membrane

Pervaporation technology is a green and novel liquid separation technology which appeared after the traditional separation techniques like distillation, absorption and extraction. It has many advantages such as energy saving, moderate cost, and environmentally friendly. It has a wide range of uses in recovery or removal small quantities of organics in water and solvent dehydration. Since it is not confined by the vapor-liquid equilibrium, it has significant advantages in the separation of azeotrope mixtures and close boiling-point mixtures. The key of pervaporation is the pervaporation membrane, so the key research of pervaporation technology is how to develop a high permeation flux membrane with a high separation factor.In this dissertation, we select the ethanol-water mixture as a separation system; prepare an ethanol permselective membrane to separate the low concentration ethanol aqueous solution and a water permselective membrane to separate the high concentration ethanol aqueous solution, respectively. The morphology and pervaporation performance of obtained membranes was investigated by FT-IR, SEM, contact angle measurement, and pervaporation equipment.We choose commercial polysulfone (PSF) ultrafiltration membrane which has good physicochemical properties and thermal stability as the basement membrane, and coat PDMS on the surface of the PSF membrane as an active layer to prepare the PDMS/PSF composite membrane for the separation of low concentration ethanol aqueous solution, then polyvinyl alcohol (PVA) aqueous solution added with graphene oxide (GO) was cross-linked on the surface of the PSF membrane employed an interfacial reaction technique to fabricate GO-PVA/PSF composite membrane for dehydration of ethanol. The preparation conditions of membrane formation and operation conditions (feed concentration, feed temperature, flow rate) that influenced on the pervaporation performance were investigated.The results are listed as follow:(1) The best concentration of casting solution to prepare PDMS/PSF composite membrane is 10 wt%. The permeation flux increased with increase of feed concentration, feed temperature, and flow rate; the separation factor increased at first and then decreased with increase of feed temperature, and reached maximum at 40℃; The separation factor increased slightly with increase of flow rate.(2) The addition of graphen oxide can improve the permselective of GO-PVA/PSF membrane to water, the preferred crosslinking agent concentration is 0.25 wt%, graphen oxide addition is 2% of PVA solid content, the concentration of PVA is 2 wt%; the permeation flux decreased and separation factor increased at first and then decreased with increase of feed concentration, and the latter reached maximum at 90 wt%, the permeation flux increased with increase of feed temperature, but the change of separation factor is special, it decreased when the feed concentration is 70 wt% and 80 wt%, but it increased at first then decreased when the feed concentration is 90 wt% and 95 wt%, and reached maximum at 50℃; the permeation flux increased but the separation factor did not change significantly with increase of flow rate.