| Water shortage is one of the most important issues all over the word. The portable water just constitutes less than1%of the whole water resource while seawater constitutes more than97%. Therefore, desalination, which can convert the seawater to the portable water, has become one of the most widely used and effective strategy to deal with the problem of the water shortage. Various techniques have been explored to be used in desalination. However, membrane based methods have overwhelmingly become the dominant desalination technique because of their stability, easy operation properties and high separation efficiency. Among all the desalination membranes, the polyamide thin film composite (PA-TFC) reverse osmosis (RO) membranes have been mostly widely used in recent decades due to their excellent properties. However, one of the problems is that the operation pressure of the PA-TFC desalination membranes is very high, which is not favor for the cost-effectiveness. Therefore, it is of great importance to secure strategies to explore novel PA-TFC desalination membranes with more cost-effectiveness properties.Many unique properties, such as small and tunable fiber diameters, large surface area and pores ratios, have make electrospun nanofibrous membranes (ENMs) exhibit promising properties in many areas, such as catalysis, sensors, and biotechnology. ENMs have also shown many applications in the filtration areas. ENMs can be directly used as microfiltration membranes and can be used as supporting layers to prepare ultrafiltration and nanofiltration composite membranes. Besides, ENMs supported PA-TFC membranes have also shown sodium chloride separation properties, indicating their promising desalination applications. Moreover, the ENMs supported filtration membranes show higher permeations and retained high separation properties compared with conventional ones. In addition, the operation pressures are always lower. Thus, the ENMs supported filtration membranes are more cost-effective and can be good candidate for preparing novel desalination membranes.In this study, a novel ENMs supported PA-TFC RO membranes by interfacial polymerization of m-Phenylenediamine (MPD) trimesoyl chloride (TMC) on the surface of chitosan coated ENMs. The effects of various factors, including the polymers, chitosan concentrations, cross-linker (glutaraldehyde, GA) concentrations, MPD and TMC concentrations, curing times, on the structures and properties of the obtained membranes were systematically investigated and the research can be divided into three parts as follows.Firstly, polyacrylonitrile (PAN) ENMs supported PA-TFC membranes were prepared by interfacial polymerization on the chitosan coated PAN ENMs. It was found that the successful preparation of the membranes is dependent on the addition of surfactant of sodium dodecyl sulfonate (SDS). Given the fact that the difference of the ENMs supported PA-TFC membranes and polysulfone (PS) casting membranes supported conventional ones is the composition of the supporting layer, two factors that influence the supporting layer (chitosan coated PAN ENMs) including chitosan and GA concentrations were systematically studied. Under the optimum conditions in this stage, the permeation can be as high as52.4L·m-2·h-1(operating pressure:0.8MPa) and the salt rejection is42.3%.Secondly, polyvinylidenefluoride (PVDF) ENMs supported PA-TFC membranes were prepared by the similar procedures mentioned above. The factors that influence the preparation of polyamide, such as MPD and TMC concentrations and curing times, were investigated. Under the optimized conditions at this stage, the permeation is16.5L·m-2·h-1(operating pressure:0.8MPa) and the salt rejection is94.4%. The separation properties of the obtained ENMs supported PA-TFC membrane are compared with that of conventional ones. Although the salt rejection is comparatively not high, the permeations are advantageous. Besides, the operating pressure of the ENMs supported PA-TFC membranes is as low as0.8MPa, which makes them very cost-effective.Thirdly, NaA zeolite particles were synthesized and incorporated into the obtained ENMs supported PA-TFC membranes. The addition of NaA zeolite particles could decrease the salt sepearation properties, but significantly increase the permeations of the obtained membranes. Meanwhile, it is found that the doping of NaA zeolite particles can effectively decrease the formation of pinholes in the obtained membranes.Overall, ENMs supported PA-TFC reverse osmosis membranes were successfully prepared by the interfacial polymerization of MPD and TMC on the surface of chitosan coated ENMs. Although the salt rejections are comparatively not high, the permeations are advantageous. Most importantly, the operating pressure of the obtained membranes is very low and makes them very cost-effective. The addition of NaA zeolite particles could decrease the salt sepearation properties, but significantly increase the permeations of the obtained membranes. Meanwhile, it is found that the doping of NaA zeolite particles can effectively decrease the formation of pinholes in the obtained membranes.The research here can provide fundamental and experimental information for the exploration of novel PA-TFC RO membranes. |
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