以雙重電性表面改質方式製作抗生物吸附之超過濾與奈米過濾膜; Low fouling ultrafiltration and nanofiltration membranes fabricated by zwitterionic surface modification

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題名:	以雙重電性表面改質方式製作抗生物吸附之超過濾與奈米過濾膜;Low fouling ultrafiltration and nanofiltration membranes fabricated by zwitterionic surface modification
作者:	江衍徹;Yen-che Chiang
貢獻者:	化學工程與材料工程研究所
關鍵詞:	奈米過濾膜;生物結垢;雙離子聚合物;nanofiltration;biofouling;zwitterionic
日期:	2009-06-18
上傳時間:	2009-09-21 12:25:44 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	對於一個理想的蛋白質超過濾薄膜而言，薄膜本身需要具有良好機械性質及很低的生物結垢特性。疏水性PVDF薄膜本身擁有良好抗化、抗熱性及機械強度，因此常被使用在各式薄膜過濾材料選擇，可是對於運用在食品或製藥程序上，薄膜表面之生物結垢(biofouling)往往是個嚴重且麻煩的問題。有鑑於此，本研究嘗試以臭氧處理活化PVDF薄膜，然後以原子自由基轉移聚合方法控制薄膜表面雙離子聚合物(polySBMA)之接枝度，藉以增加疏水薄膜的親水性並降低其生物結垢性質。實驗中，我們選擇牛血清蛋白(Bovine Serum Albumin, BSA )及較為黏滯性的γ-globulin當作標的蛋白，以靜態吸附以及三次循環過濾測試證實PVDF-g-PSBMA薄膜具有優越之抗蛋白吸附性質。另外對於高通透量之奈米過濾膜製備，本實驗利用樹枝狀(hyperbranch)構造之水相高分子polyethyleneimine(PEI)與油相單體trimesoyl chloride(TMC)、terephthaloyl chloride(TPC)進行界面聚合反應，其水相分子的胺基(-NH2)與油相單體的醯氯基(O=C-Cl)所形成高緻密的醯胺鍵網狀結構，將可阻擋一些分子量大於100的小分子，因此水相PEI分子量、濃度、與界面聚合反應時間都將會影響選擇層的性質，所以這些變因將是探討重點，另外對於經四級胺化改質後薄膜表面帶電量與環境pH值變化造成薄膜電性轉換，我們也做進一步分析。最後PEI系列薄膜與另外兩種ethylenediamine(EDA)/TMC、diethylenetriamine(DETA)/TMC奈米過濾膜將互相比較單鹽截留行為，結果發現PEI/TPC具有與EDA/TMC薄膜相似大小孔徑，但鹽類截留率與純水permeability卻都高於EDA/TMC薄膜；另外PEI/TMC薄膜約為1.5nm，此孔洞遠大於EDA/TMC (rp = 0.43nm)薄膜，但卻仍有比較高的NaCl截留率。此現象有可能是PEI特殊的樹枝狀結構造成奈米過濾膜具有高截留性與高通透量主要原因。最後若是奈米過濾膜應用於廢水處理或生物反應器系統，其薄膜因微生物生物堵塞(biofouling)往往是一個嚴重的問題，為了解決降低biofouling問題，本研究嘗試創造正負電性相當之雙離子性薄膜，並以蛋白質吸附實驗及革蘭氏陰、陽細菌貼附實驗證明biofouling現象已大幅降低。實驗中選用自製的DETA/TMC奈米過濾膜並利用iodopropionic acid (IPA)進行表面N-alkylation反應，其薄膜結構中三級胺官能基部分，隨後再以iodomethane進行四級胺化改質，並調控薄膜表面正負電荷比例，最後以元素分析儀(XPS)與界達電位量測證明膜面改質成功。在蛋白質吸附實驗部分，我們選擇BSA( pI =4.9 )與Lysozyme( pI=10.5 )對薄膜進行吸附測試，結果只有表面接近電中性的QDETA-IPA25%薄膜對兩種蛋白都具有抗吸附效果，而在革蘭氏陰、陽細菌貼附實驗中，除了負電性薄膜DETA-IPA5%與DETA-IPA25%具有良好抗吸附外，電中性薄膜QDETA-IPA25%同樣也有降低細菌吸附表現，我們認為雙離子QDETA-IPA25%薄膜將來有機會可以運用於生物反應器系統。 In addition to sharp molecular weight cut and high flux an ideal ultrafiltration (UF) membrane requires high mechanical strength, good chemical resistance as well as anti-fouling characteristics. Poly(vinylidene fluroride) (PVDF) is often chosen to prepare UF membranes owing to its good mechanical properties and excellent chemical resistance. To retain the merits of PVDF UF membrane properties, we try to graft antifouling poly sulfobetaine onto the surface of the PVDF UF membrane. The zwitterionic sulfobetaine methacrylate (SBMA) was grafted on the surface of PVDF membrane via ozone surface activation and surface-initiated atom transfer radical polymerization (ATRP). The steady adsorption of bovine serum albumin (BSA) and γ-globulin were performed to test the antifouling character after SBMA grafting. Hardly any albumin adsorption was found as the grafting density exceeded 0.4 mg/cm2 of polySBMA. The adsorption of?γ-globulin was also greatly reduced. To investigate whether the method, ozone surface activation plus ATRP, was able to graft SBMA inside the pores of the membrane cyclic filtration tests were performed and the UF membrane of wider pore size was used. The cyclic filtration test for BSA yielded an extremely low irreversible membrane fouling ratio (Rir) of 13% in the first cycle and apparently no irreversible fouling was found in the second cycle. A more stringent test is carried out by passing the γ-globulin solution. It was found that the virgin PVDF membrane was continuously fouled by γ-globulin after 3 cyclic operations, but the polySBMA modified membrane had a Rir value as low as 4.7% in the third cycle. The results indicated that the surface modification via ozone surface activation and ATRP could actually penetrate into the pores of an ultrafiltration membrane. The polySBMA grafted PVDF membrane could effectively resist plasma protein adsorption and exhibited an extremely low biofouling characteristic during filtration. Four nanofiltration membranes, two negatively and two positively charged, were fabricated by interfacial polymerization. Three different amines, ethylendiamine (EDA), diethylentriamine (DETA), and hyperbranched polyethylenimine (PEI) were selected to react with two acyl chlorides, trimesoyl chloride (TMC) and terephthaloyl chloride. The two membranes containing hyperbranched PEI, PEI/TPC and PEI/TMC, are positively charged at the operational pH. But the other two membranes, EDA/TMC and DETA/TMC, are negatively charged. It is found that the two PEI membranes own special rejection characters during nanofiltration. The PEI/TPC membrane has a similar pore size to the EDA/TMC membrane but owns simultaneously the higher salt rejection and permeation flux. The PEI/TMC has a pore size as big as 1.5 nm and still has a higher NaCl rejection than the EDA/TMC membrane of which the pore size is as small as 0.43 nm. We consider that the special rejection characters are derived from the special structure of PEI. The hyperbranched structure allows some of the charged amine groups drifting inside the pores and interacting with the ions in the pathway. The drifting amines increase salt rejection but have little effect on water permeation. It imply that a high flux and high rejection membrane for desalting can be obtained by attaching freely rotating charged groups. Membrane fouling is a fatal problem in membrane filtration operation. Biofouling is especially notorious. In order to reduce the biofouling on a nanofiltration membrane, we tried to create a hydrophilic surface fixed with balanced positive and negative charges. Nanofiltration membranes were fabricated by interfacial polymerization of Trimesic acid Trichloride (TMC) and Diethylenetriamine (DETA). The surfaces were then modified via N-alkylation of the secondary amine with iodopropionic acid (IPA). The resulting tertiary amines were further quaternized by iodomethane. Negatively charged Bovine Serum Albumin (BSA) and positively charged lysozyme (LYS) were used to test the protein fouling probability. The membranes of various degree of N-alkylation or quarternation exhibited different levels of protein adsorption. The DETA/TMC nanofiltration membrane adsorbed moderate amount of both BSA and LYS. After reacting with iodopropionic acid the BSA adsorption greatly decreased but the adsorption of LYS raised. After quarternization the membrane moderately modified by iodopropionic acid adsorbed little LYS but large amount of BSA. Only the membrane highly modified by IPA and moderately quarternized by iodomethane exhibits excellent resistant against both positively and negatively charged proteins. The protein resistant neutral membrane(QDETA-IPA25%) also showed reduced adsorption of E. coli and S. epidermidis. The results indicated the importance of charge balance on the membrane surface in view of protein fouling and bacteria adhesion.
顯示於類別:	[化學工程與材料工程研究所] 博碩士論文

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