Preparation Of Sulfonation Cardo Polyetherketone-based Forward Osmosis Membranes And Study On Their Forward Osmosis Performance

Forward Osmosis（FO）,as a new water treatment technology developed in recent decades,has the advantages of low energy consumption,small membrane pollution and environmental friendliness compared with traditional water treatment technology.And FO shows great potential in wastewater treatment,seawater desalination,osmotic power generation,food concentration,drug release and so on.The key of this new water treatment technology is the appropriate FO membrane and draw solution,yet the concentration polarization in FO process leads to smaller water flux,and no effective way to economic recovery draw liquid limit its commercial application.In this paper,several kinds of FO membranes were prepared by using sulfonation cardo polyetherketone as membrane-forming material,and the FO permeability of the membranes was investigated.The magnetic particles coated by carbon dots as draw solute were prepared,and its driving performance in FO process was also investigated.The main researches are listed as follows:（1）The SPEK-C FO flat sheet membrane was fabricated by cast spin coating method using sulfonation cardo polyetherketone（SPEK-C）as membrane-forming material,polyvinylpyrrolidone K30（PVP）as additive,and N-methyl pyrrolidone（NMP）as solvent.SPEK-C FO membrane was characterized by contact angle（CA）,scanning electron microscopy（SEM）,atomic force microscopy（AFM）,infrared spectroscopy（FT-IR）,and its performances were also investigated.The experimental results show that the SPEK-C FO membrane present the best FO performance,when the degree of sulfonation of SPEK-C is 2.14,the content of SPEK-C is 14 wt%,the content of PVP is 3 wt%.Accordingly,with deionized water as feed solution,2 mol/L Na Cl solution as draw solution,and liquid flow rate on the both sides of membrane of250 ml/min,the water flux and salt flux is 31.23 L.m^-2.h^-1and 12.32 g.m^-2.h^-1,respectively.（2）With SPEK-C/PVP/NMP as casting membrane solution and nylon cloth as support layer,the SPEK-C composite membrane was prepared by coating method,and it was characterized by CA,SEM,AFM and FT-IR methods.Meanwhile,the performance of the SPEK-C composite membrane was also test.The experimental results show that the SPEK-C composite membrane has the best permeate performance when the mesh of nylon cloth is 300,and the casting solution is prepared of 14 wt%SPEK-C,3 wt%PVP and 83 wt%NMP.The water flux and the salt flux of the SPEK-C composite membrane is 77.75 L.m^-2.h^-1and 29.57 g.m^-2.h^-1,respectively,when deionized water is used as feed solution,2 mol/L Na Cl solution as draw solution,and the liquid flow rate on the both sides of membrane is 250 ml/min.（3）Using 14 wt%SPEK-C,3 wt%acetone and 83 wt%NMP as casting membrane solution and nylon cloth of 300 mesh as support layer to fabricated the basement membrane,the polyamide/SPEK-C FO composite membrane was prepared by interfacial polymerization,and it was characterized by CA,SEM and AFM methods.The effects of interfacial polymerization time,concentration of draw solution and the liquid flow rate on both sides of the membrane on the FO permeability of membrane were investigated.The experimental results show that the polyamide/SPEK-C FO composite membrane prepared with the interface polymerization time of 2 min presents the best permeate performance.Using deionized water as feed solution,2 mol/L Na Cl as draw solution,and liquid flow rate on both sides of the membrane of 250 ml/min,the water flux of the composite membrane is 71.01 L.m^-2.h^-1,and salt flux is 8.23 g.m^-2.h^-1.（4）The magnetic Fe₃O₄particles were prepared by hydrothermal method,and carbon quantum dots（CDs）were prepared by pyrolysis metold.CDs@Fe₃O₄magnetic particles were prepared by loaded CDs on the surface of magnetic Fe₃O₄particles,and characterized by transmission electron microscopy（TEM）,nanometer particle size analyzer（Zetasizer）,FT-IR and magnetic property measurement system（MPMS）.The effects of draw solution concentration and feed concentration on the FO process with magnetic CDs@Fe₃O₄particles as draw solution and PEG-400 solution as feed were investigated.The experimental results show that a lower feed solution concentration or a larger draw solution concentration can improve the FO performance.When the feed solution is PEG-400 aqueous solution with a volume fraction of 2%,the draw solution is 2.0 g/L magnetic CDs@Fe₃O₄particles,and liquid flow rate on both sides of membrane is 250 ml/min,the water flux of SPEK-C composite membrane is 58.43 L.m^-2.h^-1.After five times usage,the water flux of SPEK-C composite membrane is only reduced to 55.31 L.m^-2.h^-1,indicating good reusability of the prepared CDs@Fe₃O₄particles.