| 摘要: | 本研究以界面聚合的方式製造出帶有陰電性的奈米過濾膜。先選用常見之高分子製膜材料PAN (polyacrylonitrile)與造孔劑PVP (polyvinylpyrrolidone)，以濕式相轉換法製備微過濾膜作為薄膜支撐層。主要分離層選用兩種不同胺基水相溶液：乙二胺 (ethylenediamine、EDA)、二乙基三胺(diethylenetriamine、DETA)與有機相單體溶液1,3,5-均三氯甲苯 (1,3,5-benzenetricarbonyl trichloride、TMC)，於支撐層上進行界面聚合反應製造出薄膜的選擇層。這兩種胺基單體將造成孔洞大小不同的兩種陰離子奈米過濾膜，製成後薄膜以不同分子量的PEG (poly(ethylene glycol))測試可知薄膜的MWCO，再經由計算可得知EDA薄膜孔洞大小約為0.43nm，而DETA薄膜孔洞大小約為0.66nm。膜表面的流線電位也証實EDA型薄膜與DETA型薄膜在進料溶液為pH6左右時，表面略帶有負電性。 在單一鹽類過濾測試方面，我們分別選用MgSO4、Na2SO4、MgCl2、NaCl四種鹽類分別對EDA型與DETA型薄膜進行過濾，兩種薄膜對於這四種鹽類截留率 (R)的排列順序皆為R（MgSO4）>R（Na2SO4）>R（MgCl2）>R（NaCl），顯示此兩種薄膜均屬於Peeters等人所敘述的第二類奈米過濾膜。 我們利用兩種混合鹽系統(MgSO4-MgCl2、MgSO4-Na2SO4)來探討不同孔洞尺寸薄膜對於混合鹽的過濾性質，改變的變數包括：鹽類混合比例、溶液離子強度。隨著混合鹽總離子強度的增加，我們會看到DETA型薄膜對於各離子截留率下降幅度較EDA型薄膜明顯。在MgSO4-MgCl2系統中，隨著進料的SO42-/Cl-的比例增加，EDA型薄膜對Cl 離子的截留率改變不大而DETA型薄膜對於Cl 離子的截留率都呈現明顯的下降； EDA型薄膜對Mg2+離子的截留率影響不大而DETA型薄膜對於Mg2+離子的截留率則上升。 對於MgSO4-Na2SO4系統而言，隨著進料的Mg2+/Na+的比例增加，由於Mg2+較強的電荷遮蔽，將使得counter-ion(Mg2+與Na+)較易通過而截留率降低，但因較大的counter-ion(Mg2+) 造成較嚴重的孔道縮減，在DETA型薄膜上發現Mg2+的截留率不降反略微上升。反之在孔洞小的EDA型薄膜上，Mg2+的截留率並沒有太大變化。 混合鹽系統的實驗使我們將Peeters等人所敘述的第二類奈米過濾膜又分為兩個子類，第IIa類如EDA型薄膜，其截留率以大小排斥為主，較不受鹽濃度或其他離子的存在而改變，第IIb類如DETA型薄膜，其截留率同時受大小排斥與靜電排斥的影響，較易受鹽濃度或其他離子的存在而改變。 In this study, we manufacture negative charge nanofiltration membranes by interfacial polymerization. At first, we use PAN (poly- acrylonitrile) and PVP (polyvinylpyrrolidone) to manufacture an ultra- filtration membrane as the support layer by wet processing phase inversion. Subsequently, we use two categories water phase solution containing amine group, ethylenediamine (EDA) and diethylenetriamine (DETA), and 1,3,5-benzenetricarbonyl trichloride(TMC) as organic phase solution to manufacture the selective layer of nanofiltration membranes by interfacial polymerization. We proceed filtration of different molecular weight of PEG to know the pore size of two categories nanofiltration membranes. From filtration of PEGs, we get that the pore size is 0.43nm for EDA type membrane and 0.6574nm for DETA type membrane from calculating. We use streaming potential method to detect the charge of the membrane surface. we can find that EDA type and DETA type membranes which are operated at pH5~7 of solution are negative charge membranes. We also use SEM image to know the surface structure of EDA type and DETA type membranes. For the filtration of single salt, we use MgSO4、Na2SO4、MgCl2、and NaCl to proceed filtration irrespectively for EDA type and DETA type membranes. We can find that EDA type and DETA type membranes showed the same salt rejection sequence：R（MgSO4）>R（Na2SO4）>R（MgCl2）>R（NaCl）. And EDA type membrane for each salt has a higher rejection than DETA type membrane. DETA type membrane for each salt has a higher permeability than EDA type membrane. We also discuss the performance of filtration of multi-salt solution from two multi-salts systems, MgSO4-MgCl2 system and MgSO4-Na2SO4 system. The variables are the mixing ratio of salts and the ionic strength of multi-salts solution. We can find that the rejection of each ion decreases with increasing the ionic strength of mixing salts solution for two multi-salts systems. The decrease of rejection for each ion from DETA type membrane is clearer than from EDA type membrane. In MgSO4-Na2SO4 multi-salts system, with increasing the ratio of SO42-/Cl- in feed solution, the rejection of chloride ion decreases clearly, the rejection of sulfate ion decreases slightly, and the rejection of magnesium ion increases clearly for EDA type and DETA type membranes. In MgSO4-MgCl2 multi-salts system, the counter ions (Mg2+ and Na+) will pass through membranes more easily because of a stronger charge hindrance of magnesium ion with increasing the ratio of Mg2+/Na+ in feed solution. But the rejection of magnesium ion has an increase tendency because magnesium ion will make clear decrease on pore size for DETA type membrane, whereas the rejection of magnesium ion has no clear change on a small pore size of EDA type membrane. In our multi-salts experiments, we can divide membrane which was the second type nanofiltration membrane advanced by Peeters and Mulder into two categories. The rejection of II-a type membrane as EDA type is controlled by size repulsion and isn’t changed easily by salt concentration or existence of other ions. The rejection of II-b type membrane as DETA type is controlled by size repulsion and charge repulsion and changed more easily by salt concentration or existence of other ions. |
