The Research On The Fabrication And Modification Of Polyvinyl Chloride/Chlorinated Polyvinyl Chloride Porous Membrane

Polyvinyl chloride (PVC) is one of the most widely used raw materials in plasticproduction with the virtues of many advantages and economical efficiency. In order toprepare membranes used in water treatment, PVC should be modified because of itsweakness such as hydrophobility and weak pressure resistance. Chlorinated polyvinylchloride (CPVC) resin is a thermoplastic produced by chlorination of PVC resin.Compared with PVC, the thermal tolerance and mechanical properties was improvedobviously. This study investigated the compatibility of the two material andhydrophilic modification method, based on which, the charged membrane, anti-fouling membrane and structural stable nanofiltration membrane was developed.The details in this paper were summarized as follows:Firstly, the compatibility of PVC and CPVC in organic solvent was studied, andPVC was blended with CPVC to fabricate ultrafiltration membrane. PEG2000andPluronic F127were chosed as surface modifier and pore forming agent to constructhydrophilic surface by surface segregation. As the CPVC proportion increased, thewater flux of PVC/CPVC blend membranes would improve while the BSA rejectionchange slightly. The F127enhanced the anti-fouling ability of PVC/CPVC membraneefficiently.Secondly, a combined technique based on ultrafiltration and adsorption isdeveloped for dye wastewater treatment. The further amination of CPVC introduceelectric charge on membrane surface which plays an important role in dye adsorption.Ethylenediamine was chose as amination agent and Orange G as probe to verify theadsorption capacity of aminated membrane which was affected by surround pH.During ultrafiltration, the rejection ratio of Orange G can reach100%in the initialoperation stage and lasted for70min at pH4due to adsorption of Orange G on thesurface and pores of membrane. The final recovery of Orange G was easily achievedby increasing the solution pH to desorb Orange G in20min.Thirdly, based on anminated membrane, fluorination treatment was achievedthrough chemical reaction between redundant amino groups on the membrane surfaceand pentadecafluorooctanoica acid (PFOA).because of the fabrication of super-hydrophilic and hydrophobic surface, the fluorinated membranes can be fully wettedby water in short time according to water contact angle measurement. In the ultralow pressure ultrafiltraion of oil/water emulsion, the oil drop was resistant by PFOAperssad, and low flux decrease (22.9%) and high flux recovery (95%) was achievedcompared with PVC/CPVC membrane.Forth, inspired by aminated membrane and interfacial polymerization, PAcomposite nanofiltration membrane was fabricated with aminated membrane as basemembrane. In this experiment, triethylene tetramine (TETA) was chosed as aminationagent and Tetraethylene pentamine (TEPA) was chosed as contrast. Apparently, theredundant amino groups on the membrane surface take part in the interfacialpolymerization, and powerful covalent bond was constructed between base aminatedmembrane and PA film which result in the stable composite membrane. Moreover, themembrane surface static water contact angle decreased to about12°, which indicates ahydrophilic surface was formed. After the24hour immersion in alcohol, thepermeation and salt rejection changed slightly. Meanwhile, the permeation of PA-PVC/CPVC increased from10.21L/m2h to14.49L/m2h and PA-TEPA-PVC/CPVCfrom8.78L/m2h to9.18L/m2h, the salt rejection decreased from86%to70%andPA-TEPA-PVC/CPVC from88.84%to85.93%.