界面聚合反应有机溶剂对聚酰胺复合纳滤膜结构及性能的影响

聚酰胺复合纳滤膜的分离性能主要由聚酰胺分离层决定。在界面聚合反应过程中,有机相溶剂的物理性质影响两相单体在界面的溶解及扩散行为,使聚酰胺分离层微观形貌结构发生变化,从而改变膜性能。以异构烷烃混合型溶剂Isopar G,Isopar H,Isopar L和Isopar M为有机相溶剂采用界面聚合法制备聚酰胺复合纳滤膜,考察上述有机相溶剂对复合纳滤膜聚酰胺交联度、分离层微观结构和聚酰胺高分子链堆积程度的影响,通过分析有机相溶剂物理性质与纳滤膜分离性能、聚酰胺层结构参数之间的相关性,探究有机相溶剂对纳滤膜分离性能的影响机制。结果表明,有机相溶剂的表面张力与聚酰胺高分子团簇的分形维数(D_(m))呈强相关性,相关性系数为-0.98;D_(m)与复合纳滤膜的水透过系数(A)呈强相关性,相关性系数为0.95,即通过选取表面张力较低的有机相溶剂,有利于提高聚酰胺高分子的分形维数,使聚酰胺具有更高的链密度,短分子链结构堆积更加疏松,从而制备具有更高水通量的聚酰胺复合纳滤膜。有机相溶剂的表面张力与A的相关性系数为-0.97,进一步印证了上述结论。

Surface modification of mesoporous silica nanoparticle with 4-triethoxysilylaniline to enhance seawater desalination properties of thin-film nanocomposite reverse osmosis membranes

Mesoporous silica nanoparticles(MSN),with higher water permeability than NaA zeolite,were used to fabricate thin-film nanocomposite(TFN)reverse osmosis(RO)membranes.However,only aminoalkyl-modified MSN and low-pressure(less than 2.1 MPa)RO membrane were investigated.In this study,aminophenyl-modified MSN(AMSN)were synthesized and used to fabricate high-pressure(5.52 MPa)RO membranes.With the increasing of AMSN dosage,the crosslinking degree of the aromatic polyamide decreased,while the hydrophilicity of the membranes increased.The membrane morphology was maintained to show a ridge-and-valley structure,with only a slight increase in membrane surface roughness.At the optimum conditions(AMSN dosage of 0.25 g/L),when compared with the pure polyamide RO membrane,the water flux of the TFN RO membrane(55.67 L/m^2/h)was increased by about 21.6%,while NaCl rejection(98.97%)was slightly decreased by only 0.29%.However,the water flux of the membranes was much lower than expected.We considered that the enhancement of RO membrane permeability is attributed to the reduction of the effective thickness of the PA layer.

Preparation of reverse osmosis membrane with high permselectivity and anti-biofouling properties for desalination

High performance is essential for the polyamide(PA)reverse osmosis(RO)membranes during the desalination process.Herein,RO membranes with high permselectivity and anti-biofouling properties were fabricated by nanoparticles incorporation and anti-biofouling grafting.Hydrotalcite(HT)incorporation was performed with a dual role,enhancing water flux and acting as grafting sites.The HT incorporation increased the water flux without sacrificing the salt rejection,compensating for the loss caused by the following grafting reaction.The exposed surface of HT acted as grafting sites for anti-biofouling agent dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride(DMOTPAC).The combination of HT incorporation and DMOTPAC grafting endowed RO membranes with high permselectivity and anti-biofouling properties.The water flux of the modified membrane PA-HT-0.06 was 49.8 L/m^(2)·h,which was 16.4%higher than that of the pristine membrane.The salt rejection of PA-HT-0.06 was 99.1%,which was comparable to that of the pristine membrane.As to the fouling of negatively charged lysozyme,the modified membrane’s water flux recovery was superior to that of the pristine membrane(e.g.86.8%of PA-HT-0.06 compared to 78.2%of PA-pristine).The sterilization rates of PA-HT-0.06 for E.coli and B.subtilis were 97.3%and 98.7%,much higher than those of the pristine membrane(24.0%for E.coli and 26.7%for B.subtilis).