Authors: PingYun Zhang Hu Yang ZhenLiang Xu YongMing Wei JunLian Guo DongGen Chen
Publish Date: 2013/01/16
Volume: 20, Issue: 2, Pages: 66-
Abstract
Polyvinylidene fluoride PVDF membranes possessing interconnected bicontinuous structures with superior mechanical properties and improved hydrophilicity were obtained from PVDF/NNdimethylacetamide DMAc/Tween 80/water systems via nonsolvent induced phase separation NIPS with 60 °C and ambient temperature casting solution Tween 80/H2O mixtures were adopted as dopant water/ethanol 5050 mass ratio and ethanol were chosen as coagulants The effects of process parameters in terms of variations in dopant contents casting solution temperatures and coagulant compositions on the phase inversion process and performance of the resultant membranes were investigated During the demixing process water diffused from the interior of Tween 80 reverse micelles resulting in an accelerated precipitation rate and surface segregation process of the polar head groups of Tween 80 The high temperature of the casting solution contributed to enhancing the diffusion rate of liquid–liquid demixing on crystallization The coagulant compositions changed the liquid–liquid and solid–liquid demixing dynamics of the casting solutions Ethanol coagulant contributed to crystallization of PVDF/DMAc/Tween 80/water systems prior to liquid–liquid demixing This delayed demixing process favored the formation of porous foliagetype top structures with fibril or lath bicontinuous fine structure of membrane bulk increasing flux and significant hydrophilicity improvement Casting solutions in water/ethanol coagulant exhibited a less delayed demixing process with both liquid–liquid demixing and crystallization resulting in formation of fine structure in the form of strings or stripes and limited hydrophilicity improvement The predominant typical α and βtype crystallinity in PVDF was attributed to the existence of dopants the high temperature of the casting solution and water/ethanol coagulant This was consistent with the superior mechanical properties of the corresponding PVDF membrane The newly developed hydrophilic PVDF membranes with superior mechanical properties and lowfouling of bovine serum albumin BSA are anticipated to be suitable not only for wastewater treatment but also for bioseparation
Keywords: