正渗透复合膜的制备及表征

通过在聚砜铸膜液中加入混合添加剂氯化锂和聚乙烯吡咯烷酮（PVP），用相转移法制备出多孔支撑层，然后通过界面聚合制备聚酰胺正渗透复合膜，重点研究了添加剂和聚砜浓度对膜结构和性能的影响。结果表明，氯化锂使得膜支撑层指状孔更加均一，提高孔隙率，并降低海绵层的厚度，提高了水通量；PVP增强了膜的亲水性，并易于成膜，在保持截盐率的同时提高了水通量；随着聚砜浓度增大，支撑层孔隙率变小，海绵状孔层变厚，生成的聚酰胺层更加致密，加重过程内浓差极化，水通量降低。采用质量分数为9%聚砜同时添加氯化锂和PVP的膜支撑层结构均一，孔隙率较大（68.0%），表面亲水性较强（接触角48.5°），优于2种商用三醋酸纤维素正渗透膜的孔隙率（32.6%和25.4%）和接触角（76.5°和73.5°）；在正渗透过程中的自制膜水通量为21.9 L/（m2·h），均高于2种商用三醋酸纤维素正渗透膜（9.5和14.4 L/（m2·h））和文献报道的正渗透复合膜通量水平，并维持了一定的截盐率（盐通量为19.9 g/（m2·h）），表现出优异的正渗透性能。

Fabrication and characterization of thin-film composite membrane for forward osmosis

Thin-film composite membranes for forward osmosis(TFC-FO) were synthesized by interfacial polymerization on top of the porous polysulfone(PSf) supporting layer films,which were prepared via phase inversion with addition of polyvinyl pyrrolidone(PVP) and lithium chloride(LiCl).The effects of PSf concentration and additives on the structure characteristics and forward osmosis performance were investigated thoroughly.The results indicate that the addition of LiCl makes the finger-like pore more uniform,reduces the thickness of sponge-like pore layer,and also promotes the porosity of supporting layer,resulting in high water flux in forward osmosis process.PVP increases the hydrophilicity of TFC-FO membrane and improves the property of membrane-formation.TFC-FO membranes with addition of PVP exhibit high water flux and low reverse salt flux.With PSf concentration increasing,the porosity of supporting layer decreases,the sponge-like pore layer thickens and polyamide active layer becomes dense,which can lead to more serious internal concentration polarization and lower water flux in FO process.The TFC-FO membrane with 9% PSf concentration and addition of PVP and LiCl exhibits more uniform,porous and hydrophilic characteristics(porosity 68.0%,contact angle 48.5°) than two commercial FO membranes(porosity 32.6% and 25.4%,contact angle 76.5° and 73.5°).Additionally,the fabricated membrane shows a high performance in FO process with low reverse salt-flux of 19.9 g/(m2·h) as well as high water-flux of 21.9 L/(m2·h),which is better than that of two commercial FO membranes(9.5 and 14.4 L/(m2·h)) and some reported TFC-FO membranes under similar testing conditions.