界面聚合聚醯胺複合膜應用於滲透蒸發分離程序之研究

Study on interfacial polymerized polyamide composite membranes for pervaporation separation processes

黃書賢(Shu-Hsien Huang)

指導教授 ： 李魁然 ； 賴君義

中原大學/工學院/化學工程學系/博士(2008年)

https://doi.org/10.6840/CYCU.2008.00403

摘要

利用不同結構之水溶性胺類單體與1,3,5-苯三醯氯(trimesoyl chloride, TMC)，於改質的聚丙烯腈(polyacrylonitrile, mPAN)非對稱膜表面上進行界面聚合反應(interfacial polymerization)，製備一系列聚醯胺複合膜，應用於滲透蒸發程序分離具共沸組成的醇類水溶液。利用傅利葉變換衰減全反射紅外光譜技術(ATR-FTIR)、掃瞄式電子顯微鏡(SEM)與原子力顯微鏡(AFM)來鑑定聚醯胺聚合層的化學結構與型態。接觸角試驗被用來量測聚醯胺聚合層的親水性與對進料溶液的親和性。本研究探討界面聚合方法與製備條件，如水相溶液溫度、熱處理條件、膨潤劑、四級胺化與單體化學結構等效應對滲透蒸發分離效能的影響，亦探討滲透蒸發操作條件，如進料溶液的濃度、溫度與種類等效應對滲透蒸發分離效能的影響。為進一步了解聚醯胺複合膜物理結構的變化，利用正子湮滅光譜技術結合可變化單一能量慢速正子束來偵測整個聚醯胺複合膜自由體積與多層結構的深度輪廓，並期望與滲透蒸發分離效能有良好的關聯性。研究結果發現，與接觸-浸漬界面聚合法(IP method I)製備的複合膜比較，浸漬-接觸界面聚合法(IP method II)所製備複合膜有較低的o-Ps生命週期τ3 (自由體積尺寸)、較高o-Ps強度I3 (自由體積數量)與較薄的聚醯胺聚合層厚度，因此，應用於滲透蒸發分離70 wt%異丙醇水溶液有較高的選擇比(αwater/IPA)與透過率。利用浸漬-接觸界面聚合法(IP method II)將溼潤的改質聚丙烯腈非對稱膜整個浸入0.1 wt%的TETA水溶液中5秒鐘，然後表面再接觸0.05 wt%的TMC有機溶液10秒鐘製成TETA-TMC/mPAN複合膜。以上述界面聚合製備程序所製得之聚醯胺複合膜應用於70 oC長時間滲透蒸發操作分離70 wt%異丙醇水溶液，經過336天的測試，透過率約2400 g/m2 h，且仍保持高透過水濃度。利用電腦程式VEPFIT四層模式來分析由都卜勒展寬能量所得之正子湮滅數據，如S參數，獲得聚醯胺複合膜的多層結構，此多層結構被分為四層: 聚醯胺聚合層(0.22 μm)、聚丙烯腈非對稱膜之緻密皮層(0.42 μm)、聚丙烯腈非對稱膜中從緻密到多孔隙的過渡層與聚丙烯腈非對稱膜之多孔隙層。對於90 wt%乙醇水溶液與70 wt%異丙醇水溶液兩系統而言，水相溶液溫度、熱處理條件、膨潤劑與四級胺化等效應可有效提升聚醯胺複合膜的透過率，且透過物水濃度幾乎不變。而對於70 wt%四氟丙醇水溶液之系統來說，上述的效應能提升聚醯胺複合膜的透過物水濃度。單體化學結構對滲透蒸發分離效能的影響是隨聚醯胺聚合層的厚度與親水性的變化而變化。

關鍵字

複合膜 ； 聚醯胺 ； 正子湮滅光譜技術 ； 滲透蒸發 ； 界面聚合

並列摘要

To improve the permeation rate of the polyamide, a series of the polyamide thin-film composite membranes are prepared by the interfacial polymerization of various water-soluble amines and trimesoyl chloride (TMC) on the surfaces of the modified polyacrylonitrile (mPAN) membranes to be applied to the pervaporation separation of the aqueous alcohol solutions. Attenuated total reflection infrared spectroscopy (ATR-FTIR), scanning electron microscope (SEM) and atomic force microscope (AFM) are used to characterize the chemical structures, morphologies and roughness of the polyamide active layers of the composite membranes. The hydrophilicity and affinity between the membrane and the feed solution are studied by the contact angle measurement. The effects of the thin film composite membrane preparation procedures and conditions during the interfacial polymerization, such as the temperature of the aqueous amine solution, the annealing condition, the swelling agent concentration, the quaternization conditions and the chemical structures of the monomers etc., on the pervaporation performance are investigated. The effects of the operation conditions of the pervaporation process such as the concentration, temperature and kinds of the feed solutions on the pervaporation performance are also studied. In order to further realize the physical structure variation of the polyamide thin-film composite membrane, the positron annihilation spectroscopy (PAS) coupled with a variable monoenergy slow positron beam is utilized to detect the depth profile of the free volume and multilayer structure through the polyamide composite membrane to correlate with the pervaporation performance. It is found that the polyamide composite membrane prepared by the IP method II − immersion-contact method has lower o-Ps lifetime τ3 (free volume size), higher o-Ps intensity I3 (free volume amount) and thinner layer thickness than that of the membrane prepared by the IP method I − contact-immersion method. Thus, the polyamide composite membrane prepared by the IP method II has both higher separation factor (αwater/IPA) and permeation rate than that of the membrane prepared by the IP method I for the pervaporation separation of 70 wt% aqueous isopropanol solutions at 25 oC. The polyamide composite membranes TETA-TMC/mPAN prepared by the IP method II (wet mPAN is entirely immersed into 0.1 wt% aqueous TETA solution for 5 sec and then the surface of that is contacted with 0.05 wt% organic TMC solution for 10 sec) are utilized for the long-term test of 70 wt% aqueous isopropanol solution at 70 oC. It exhibits that the permeation rate is about 2400 g/m2 h and maintain high water concentration in permeate during 336 days operation. The positron annihilation data, such as S parameter, from Doppler broadening energy spectra (DBES) are analyzed by VEPFIT program in four-layer model to obtain the multilayer structure of the polyamide composite membrane prepared by the IP method II. The multilayer structure divided into four layers is as follows: the polyamide active layer (0.22 μm), the skin layer of mPAN (0.42 μm), a transition layer from skin layer to porous support layer of mPAN, and the porous support layer of mPAN. The effects of the aqueous amine solution temperature, annealing condition, swelling agent and quaternization can improve the permeation rate with maintaining the water concentration in permeate for the 90 wt% ethanol/water and 70 wt% isopropanol/water solutions. The above-mentioned effects for 70 wt% tetrafluoropropanol can improve the water concentration in permeate. The pervaporation performance affected by the chemical structures of the monomers is dependent on the thickness and hydrophilicity of the polyamide active layer.

並列關鍵字

interfacial polymerization ； composite membrane ； pervaporation ； polyamide ； positron annihilation spectroscopy

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