- 學位論文
界面聚合聚醯胺複合膜應用於正向滲透分離
Study on interfacially-polymerized polyamide composite membranes for forward osmosis processes
摘要
為了針對正向滲透程序，設計出高效能的聚醯胺複合薄膜，本研究係以不同結構之胺單體m-Phenylenediamine(MPD)、1,3-Diaminopropane (DAPE)、Triethylenetetramine (TETA)以及Nitrilotriethylamine(NTEA)與醯氯單體1,3,5-Benzenetricarbonyl trichloride(TMC)，在改質的聚碸非對稱基材膜表面進行界面聚合反應，製備出一系列聚醯胺/聚碸複合膜，應用於正向滲透程序分離測試。研究中利用原子力顯微鏡(AFM)、X射線光電子能譜儀(XPS)與掃描式電子顯微鏡(SEM)來鑑定聚醯胺聚合層的化學結構與型態，並且進一步利用新穎的分析技術-正子湮滅光譜技術分析不同化學結構之胺單體對於聚醯胺層結構的影響。接觸角試驗被用來量測聚醯胺聚合層與水的親和性。 研究中發現化學結構相異的胺單體其胺基數量以及所造成的立體障礙效應，將導致聚醯胺聚合層之結構型態與化學性質產生影響。由可變單一能量慢速正子束(Varible monoenergy slow positron beam，VMSPB)分析結果可以得知，化學結構相異的聚醯胺複合薄膜具有不同層間自由體積變化，且此變化與複合薄膜之正向滲透分離效能有良好的關聯性。 由正向滲透的實驗結果顯示，MPD-TMC/mPSf複合薄膜，因為所形成之芳香族聚醯胺選擇層，由於芳香聚醯胺具有僵硬的苯環結構，，而有較低的自由體積，使得食鹽不易逆擴散至汲取端，並且選擇層較薄，在 1.5M NaCl作為汲取液以及去離子水做為進料的情況下，能維持24.6LMH的水通量，而NTEA-TMC/mPSf複合薄膜，雖然有高達35.95LMH水通量，但因為其胺單體是屬於網狀的結構，具有較大的立體障礙，擁有四種聚醯胺選擇層當中最大的自由體積，進而造成大量的食鹽逆擴散至進料端。
並列摘要
To design high-performance polyamide composite films for forward osmosis, various amine monomers (i.e., m-phenylenediamine (MPD), 1,3-diaminopropane (DAPE), triethylenetetramine (TETA), and nitrilotriethylamine (NTEA)) and an acyl chloride monomer (i.e., 1,3,5-benzenetricarbonyl trichloride (TMC)) were used in this study for inducing interfacial polymerization on the surfaces of modified asymmetric polysulfone substrate film to fabricate a series of polyamide–polysulfone composite films, which were employed for testing forward osmosis separation. In this study, an atomic force microscope, X-ray photoelectron spectroscope, and scanning electron microscope were used to determine the chemical structure and morphology of polyamide polymers. In addition, a novel technique—positron annihilation spectroscopy—was applied to examine the effects of various amine monomers on the structure of polyamide polymers, and a contact angle test was performed to measure the water-affinity of polyamide polymers. This study found that the numbers of amines on amine monomers with distinct chemical structures and the resulting steric hindrance affected the structural morphology and chemical properties of polyamide polymers. By using a variable monoenergy slow positron beam (VMSPB), free volume between layers of a polyamide composite film was found to vary among various types of film. This variation was positively related to forward osmosis separation. According to the experiment results regarding forward osmosis, a selective layer composed of aromatic polyamide was formed on the MPD–TMC/mPSf composite film. Because aromatic polyamide possesses a rigid benzene structure that has long straight crystals with molecules arranged in the same direction, free volume in the composite film was low, thereby hindering the back diffusion of salts to the draw end. In addition, because the selective layer was thin, when 1.5 m NaCL was used as the draw solution and deionized water as the feed solution, a water flux of 24.6 liters per meter squared per hour (LMH) was maintained. Although an NTEA–TMC/mPSf composite film had a 35.95-LMH water flux, it caused a large amount of salts to back diffuse to the feed end because its amine monomer is a reticular structure with a large steric hindrance and the largest free volume among the four types of polyamide selective layers. An excellent forward-osmosis composite film must have high water flux and maintain a low back-diffusion rate for salts. If the back-diffusion rate for salts is high, the salt concentration at the draw end reduces, thereby increasing the costs for forward osmosis processes.