本實驗選用PVDF作為奈米過濾膜的基材膜，PVDF本身抗化性佳，所以不易在PVDF膜上進行界面聚合反應製備奈米過濾分離層。故本研究利用臭氧活化PVDF膜表面，在其表面進行自由基聚合反應接枝上丙烯胺，丙烯胺分子結構上具有一級胺基，再利用此胺基和diethylenetriamine(DETA)或polyethylenimine(PEI)與Trimesoyl chloride(TMC)及Cyanuric chloride(CC)進行界面聚合反應。 本實驗製膜程序，丙烯胺接枝膜、聚醯胺分離層及三聚氰胺分離層則分別可由傅立葉紅外線光譜儀鑑定其結構，藉由掃瞄式電子顯微鏡可觀測橫截面結構型態，進而估算出膜厚，可得知PEI型薄膜膜厚約為1.25μm，DETA型薄膜膜厚約為1.05μm。另外從MWCO測試，因PEI型薄膜高分子特性，其膜孔較大，從單鹽溶液的過濾表現可發現，DETA型薄膜對於R(MgCl2)的截留率為94.8%，PEI型薄膜對於R(MgCl2)的截留率為83.2%，兩者的鹽類截留率順序則都為R(MgCl2)>R(MgSO4)>R(NaCl)>R(Na2SO4)，另外從聚醯胺類薄膜的鹽類截留表現，本實驗以改質疏水性PVDF作為基材膜是可行的。 CC型薄膜所製備出的奈米過濾膜分離層膜孔較緻密，膜厚則與TMC型相差不大，其因為膜孔小，硫酸根易因為靜電吸引力而造成膜表面靜電遮蔽，故鹽類截留率順序為R(MgCl2)>R(NaCl)>R(MgSO4)>R(Na2SO4)。從抗氯及耐鹼測試中可發現，CC型薄膜從其通透量的下降量可發現，其對於氯的耐受性可保持在200ppm 的NaClO溶液中長達96小時，而對於鹼的耐受性則只有24小時。 One of the critical steps in fabricating a nanofiltration membrane is to firmly attach the separating layer on a ultrafiltration membrane. We suggest here a strategy to attach the hydrophilic separating layer on a hydrophobic support. Allylamine was first grafted onto the polyvinyldifluoride support through ozone surface activation and the following free radical polymerization. Primary amines in polyallylamine layer provided hinges to firmly grasp the interfacially polymerized layer. Positively charged nanofiltration membranes were fabricated by interfacial polymerization. Trimesoyl chloride (TMC) and cyanuric chloride (CC) were selected to be the monomer in the organic phase. Polyethylenimine(PEI) and diethylenetriamine (DETA) was adopted to be the monomer in the aqueous phase. Interfacial polymerization occurs at the interface between organic and aqueous phase to form a thin layer. In this study, Fourier transformed infrared attenuated total reflection spectroscopy (FTIR-ATR) was employed to characterize the nanofiltration layer. Scanning electron microscopy (SEM) was applied to determine the thickness of the nanofltration layer. PEI type membrane, 1.25μm, was thicker than DETA type membrane, 1.05μm. PEI type membrane also has bigger pore size than DETA type membrane from MWCO test. Flux and salt rejection performance were determined by dead-end filtration. The salt rejection order for polyamide type nanofiltration membrane in this study were R(MgCl2)>R(MgSO4)>R(NaCl)>R(Na2SO4) which was dominated by Donnan exclusion. In this study, I have successfully fabricated a nanofiltration layer on allylamine grafted PVDF membrane from the salt rejection performance. The salt rejection order for CC type membrane was R(MgCl2)>R(NaCl)>R(MgSO4)>R(Na2SO4). CC type membrane also shows good chlorine tolerance for 96hrs chlorine exposure. But it only can tolerate alkaline exposure for 24hrs.
