层层组装界面聚合制备聚酰胺复合正渗透膜研究

发布时间：2018-04-03 00:12

  本文选题：聚丙烯腈　切入点：层层组装　出处：《东华大学》2017年硕士论文

【摘要】：正渗透(Forward osmosis,FO)技术作为一种新型膜分离技术,在污水深度处理领域具有很大的应用潜力,正渗透膜的制备是正渗透技术研究的热点。本研究通过相转化法制备出粗糙度较低、渗透通量较高的聚丙烯腈(PAN)支撑层,在支撑层表面考察界面聚合的次数和碳纳米管浓度对所制备复合正渗透膜性能的影响,以提高正渗透膜的分离性能,并采用复合正渗透膜对二沉池出水的深度处理效果进行了探讨,论文结果可为城市污水的深度处理提供技术参考。首先,利用相转化法制备聚丙烯腈(PAN)基膜,对其碱性水解后,分别置于聚乙烯亚胺(PEI)、聚丙烯酸(PAA)溶液中,进行接枝反应制得PAN-PEI/PAA支撑层。分别采用扫描电镜、原子力显微镜进行表面形貌分析,傅里叶红外光谱、Zeta电位、接触角和拉伸强度对支撑层结构进行分析,并测的支撑层纯水通量为175.2 L/m2·h。其次,采用层层组装技术对界面聚合法进行优化,考察界面聚合次数对聚酰胺复合膜结构性能的影响。分析可知:随着界面聚合次数的增加,活性分离层致密性逐渐增加,粗糙度逐渐增大;接触角、Zeta电位逐渐降低,机械性能逐渐增强;分离性能测试可知,随着界面聚合次数的增加,反渗透水通量逐渐减小,盐截留率(R)逐渐增大,FO水通量(Jw)和盐逆向通量(Js)均逐渐降低,但盐逆向通量与水通量比(Js/Jw)呈现先减小后增大的趋势。结果表明二次界面聚合所制备的复合膜的正渗透性能最好,Jw达到16.97L/m2·h,Js为6.02g/m2·h,Js/Jw为0.35 g/L。再次,为改善正渗透膜的性能,将碳纳米管(CNTs)添加至复合膜活性分离层中,考察正渗透膜性能的变化。研究可知:随着CNTs浓度的增加,活性分离层出现絮状物质且逐渐增多,粗糙度逐渐增大;红外分析和XPS分析表明CNTs成功嵌入正渗透膜活性分离层中;亲水性能随着CNTs含量的增加而增大。采用正渗透测试装置对复合正渗透膜的分离性能进行分析可知,随着CNTs浓度的增大,水通量值随之增大。当CNTs的浓度为0.2 wt%时,制备正渗透膜的分离性能较好,Js可以达到25.14 L/m2·h,Jw为8.64 g/m2·h,Js/Jw值为0.37 g/L,CNTs添加量为0.2 wt%条件下制备的正渗透膜与三种商业膜(CTA-ES、TFC-ES、CTA-NW)进行对比,可知制备的正渗透膜在短时间运行条件下,水通量和正渗透分离性能均优于三种商业膜。最后,考察二次界面聚合制备的正渗透膜(TFC)、加入碳纳米管后正渗透膜(TFN)对二沉池出水中污染物的截留效果以及正渗透性能变化。结果表明TFN的水通量大于TFC的水通量,但TFC正渗透膜对污染物的截留效果好于TFN正渗透膜,两者对于TOC、TP和TN的截留效果达到60%之上,对于氨氮的截留率在50%左右。
[Abstract]:As a new membrane separation technology, forward osmosis FOO (forward osmosis) technology has great application potential in the field of advanced wastewater treatment. The preparation of forward osmotic membrane is a hot topic in the research of forward osmotic technology.The polyacrylonitrile (pan) support layer with low roughness and high permeation flux was prepared by phase inversion method. The effects of interfacial polymerization times and carbon nanotube concentration on the properties of the composite membrane were investigated on the surface of the support layer.In order to improve the separation performance of normal-osmotic membrane, the effect of advanced treatment of secondary sedimentation tank effluent was discussed by using composite normal-osmotic membrane. The results of this paper can provide technical reference for advanced treatment of municipal sewage.Firstly, the polyacrylonitrile (pan) base film was prepared by phase inversion method. After alkaline hydrolysis, the polyacrylonitrile (pan) substrate was prepared by grafting reaction in the solution of polyimide (PEI) and polyacrylic acid (PAA) respectively.The surface morphology was analyzed by scanning electron microscope (SEM) and atomic force microscope (AFM). The structure of the support layer was analyzed by Fourier transform infrared spectroscopy (FTIR) potential, contact angle and tensile strength. The pure water flux of the support layer was measured to be 175.2 L/m2 / h.Secondly, the interfacial polymerization method was optimized by layer-by-layer assembly technique, and the influence of interfacial polymerization times on the structure and properties of polyamide composite membrane was investigated.The results show that with the increase of interfacial polymerization times, the densification and roughness of the active separation layer increase gradually, the Zeta potential of contact angle decreases and the mechanical properties increase.With the increase of interfacial polymerization times, the reverse osmosis water flux decreases, the salt rejection ratio (R) increases, the water flux of FO and the reverse flux of salt decrease gradually, but the ratio of reverse flux of salt to water flux decreases first and then increases.The results show that the composite membranes prepared by the secondary interfacial polymerization have the best forward osmotic properties (J w = 16.97L/m2 HN / J s = 6.02g/m2 HS / J w = 0.35 g / L).Thirdly, in order to improve the performance of the membrane, CNTswas added to the active separation layer of the composite membrane, and the change of the performance of the membrane was investigated.The results showed that with the increase of CNTs concentration, flocculants appeared in the active separation layer, and the roughness increased gradually, and the IR and XPS analysis showed that CNTs was successfully embedded in the active separation layer of the normal osmotic membrane.The hydrophilic energy increases with the increase of CNTs content.The separation performance of composite normal osmotic membrane was analyzed by using the normal osmotic test device. The water flux increased with the increase of CNTs concentration.褰揅NTs鐨勬祿搴︿负0.2 wt%鏃，

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