Pervaporative Separation Of Benzene And Cyclohexane Mixtures Through Modified Poly (Vinyl Alcohol) Membranes

Pervaporation, as a novel liquid mixture separation technology, has outstandingtechnical advantages and promising application prospects in the separation oforganic-organic mixtures. Separation performance of pervaporation process mainlydepends on the property of membrane. Selecting the appropriate material withexcellent separation performance is an important issue in pervaporation research.In our work, poly (vinyl alcohol) (PVA) was chosen out as the bulk membranematerial considering the solution parameters, chemical structures, propertiesdifference of benzene and cyclohexane. A series of PVA membranes filled with carbonnanotubes (CNTs), carbon graphite (CG) and carbon molecular sieve (CMS) wereprepared to pervaporative separateion of benzene/cyclohexane (Bz/Chx) mixtures.Theeffects of filler type, filler content in membranes and filler particle size on swellingbehavior and pervaporation performance of the filled membranes were investigated.Moreover, effects of operating conditions (weight fraction of benzene in feed, feedtemperature and feed flow rate) on swelling behavior and pervaporation performancewere studied. The filled PVA membranes showed much better separation performancethan unfilled PVA membrane. Among the three types filled PVA membranes, theperformance of CG-PVA membrane was the best. The separation factor was 100.1 andtotal permeation flux was 90.7g/(m~2h), when the CG-PVA membrane contained6.0wt% CG pervaporative separation of 50wt% Bz/Chx mixtures at 323K, keepingfeed flow rate 60L/h, downstream pressure below 0.1kPa.The structure morphology, the physical and chemical characteristics of the filledPVA membranes were obtained by FT-IR, XRD, SEM, TG/DTG and DMA. Therelationships between properties of filled membrane material and separationperformance of the membranes were discussed.In addition, poly (vinyl alcohol)/chitosan (PVA/CS) blend membranes wereprepared by mixing the two polymeric homogeneous solutions. The properties ofblend membranes and interaction between PVA and chitosan were studied by intrinsicviscosity determination. Then effects of chitosan content in membrane and operatingconditions on swelling behavior and pervaporation performance of PVA/CSmembranes were investigated. The separation factor and total permeation flux of theblend membrane containing 50wt% chitosan were 49.9 and 51.4g/ (m~2h), respectively,at 323K, keeping feed flow rate 60L/h anddownstream pressure below 0.1kPa.