【作者】 董倩；

【导师】 张卫东； 谢化允；

【作者基本信息】 北京化工大学 ， 化学工程（专业学位）， 2020， 硕士

【摘要】 反渗透技术是一项高效成熟的膜分离技术,其核心是性能优良的反渗透膜。反渗透过程中为了抑制膜的生物污染,常向进料液中添加活性氯进行杀菌预处理。目前通用的聚酰胺反渗透膜由于分子链的化学结构,极易受到活性氯攻击而导致膜性能劣化,缩短了膜的使用寿命,严重限制了反渗透技术的应用和发展。因此,开发高耐氯性反渗透膜具有十分重要的意义。本文在深入研究芳香聚酰胺反渗透膜氯化机理的基础上,认为氨基邻位存在甲基(-CH3)的芳香族二胺化合物可以增大氯化反应的空间位阻,提高聚酰胺的耐氯性,由此选择了一种新的功能单体甲基间苯二胺(MMPD),通过界面聚合法与多元酰氯TMC反应制备得到MMPD-TMC反渗透膜。借助通量和脱盐率两个指标的变化情况,探索聚合反应的条件对膜性能的直观影响。考察了单体浓度、水相溶液pH值、界面聚合时间、热处理温度、热处理时间等制膜工艺条件对复合膜分离性能的影响。确定了最优的制膜条件:水相单体(MMPD)浓度为2.0 wt.%,有机相单体(TMC)浓度0.20 wt.%,水相溶液pH值为9.0,界面聚合时间60 s,热处理温度为80℃,热处理时间10 min。分离实验表明,优化后的反渗透膜在进料液浓度2 g·L-1、操作压力1.2 MPa的条件下,纯水通量为36.3 L·m-2·h-1·MPa-1,脱盐率为95.1%,性能与商业反渗透膜相差不大。采用扫描电镜(SEM)、接触角测试(CA)、X射线衍射(XRD)以及热重分析(TGA)等手段对所制备的反渗透膜进行了表征。最后,采用活性氯浸泡法测试了所制备的MMPD-TMC反渗透膜的耐氯性能。经过20000 ppm·h的活性氯处理后,MMPD-TMC膜未发生明显的氯化,纯水通量和脱盐率仍能保持稳定;而商业反渗透膜发生了明显的氯化,纯水通量急剧增加,脱盐率大大下降。MMPD-TMC反渗透膜与商业反渗透膜相比,耐氯性能提高。更多还原

【Abstract】 Reverse osmosis(RO)technology is an efficient and mature membrane separation technology,and its core is the high functional RO membrane.However,in order to prevent the bio-fouling of the membrane,researchers of reverse osmosis usually adopt preliminary sterilization by adding active chlorine into the feed liquid.The conventional polyamide RO membrane is susceptible to free chlorine due to the chemical structure.The free chlorine in RO feed stream can cause deterioration of membrane performance,which shortens membrane life and greatly limits the development and application of RO technology.Therefore,it is of great significance to develop RO membrane with high chlorine resistance.In this work,the chlorination mechanism of polyamide RO membrane was clarified and monomer methyl-m-phenylenediamine(MMPD)was selected to prepare the composite RO membrane via interfacial polymerization and reaction with polyacyl chloride TMC.It was considerated that the aromatic diamine compound MMPD with a CH3 substituent at the ortho position of the amino would produce the polyamide possessing an improved chlorine resistance.The effects of monomer concentration,pH of aqueous solution,interfacial polymerization time,curing temperature and curing time on membrane separation performance were investigated.The optimal preparation conditions were determined:the aqueous phase monomer(MMPD)concentration is 2.0 wt.%,the organic phase monomer(TMC)concentration is 0.20 wt.%,aqueous solution pH value is 9.0,interfacial polymerization time is 60 s,curing temperature is 80℃,curing time is 10 min.The optimal conditions for preparing the RO membrane in the feed concentration of 2 g·L-1 and the pressure under the condition of 1.2 MPa,the retention rate of NaCl is 95.1%,reverse osmosis membrane flux is 36.3 L·m-2·h-1MPa-1.The RO performance of MMPD-TMC membrane was comparable to that of MPD-TMC membrane.The MMPD-TMC membrane was characterized by SEM,CA,XRD and TGA.In addition,the chlorine resistance of MMPD-TMC membrane was analyzed by adjusting the concentration of sodium hypochlorite.After the MMPD-TMC membranes were treated with 20000 ppm·h chlorine,the chlorination of crosslinked aromatic polyamides can be neglected as compared with the chlorination of MPD-TMC membranes,and the water flux and salt rejection remained stable.That is to say,compared with commercial RO membrane,MMPD-TMC membrane possessed relatively high chlorine resistance.更多还原