聚醯胺/醋酸纖維酯複合膜應用於滲透蒸發分離之研究

Study on polyamide/cellulose acetate composite membrane for pervaporation separation

魏士偉(Shi-Wei Wei)

指導教授 ： ARRAY(0xc145ed8)

中原大學/工學院/化學工程研究所/碩士(2009年)

https://doi.org/10.6840/cycu200901070

摘要

為了改善聚醯胺(polyamide. PA)薄膜低透過量的缺點，本研究利用不同結構之胺單體(DMDPA、NTEA、DETA)與不同結構之醯氯單體(DEMDC、PC、TMC)，於親水的非對稱醋酸纖維酯(cellulose acetate, CA)薄膜表面進行界面聚合反應，製備一系列聚醯胺/醋酸纖維酯複合膜，應用於滲透蒸發程序分離醇類水溶液。研究中利用全反射式傅立葉轉換紅外線光譜儀(ATR-FTIR)、X射線光電子能譜儀(XPS)與掃瞄式電子顯微鏡(SEM)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與對進料溶液的親和性。
研究中探討單體結構與聚合條件，例如：水相與有機相單體溶液濃度、水相處理時間、聚合時間、有機相溶劑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，例如：操作壓力、進料溶液組成、溫度與種類等效應對滲透蒸發分離效能的影響。研究發現不同單體化學結構所造成反應性及立體障礙的差異，主導聚合層結構型態與交聯程度，而理想的單體組合為胺單體 DETA與醯氯單體 TMC。
在探討以不同有機相溶劑所製備聚醯胺層之結構變化與滲透蒸發分離效能的關聯性研究中發現，隨著有機相溶劑黏度下降，聚醯胺層厚度隨之增加，滲透蒸發效能呈現透過量下降而透過水濃度上升的趨勢。為進一步了解有機相溶劑對聚醯胺聚合層細微結構的影響，利用正子湮滅光譜分析技術(Positron annihilation spectroscopy, PAS)使用可變單一能量慢速正子束(Variable monoenergy slow positron beam, VMSPB)分析儀來偵測聚醯胺複合膜其聚合層之自由體積與結構變化，並期望與滲透蒸發分離效能有良好的關聯性。
研究結果顯示，CA基材膜浸泡於0.5 wt% DETA水溶液中10秒，然後表面接觸0.5 wt% TMC/iso-pentane有機溶液進行界面聚合反應10秒，所製得之複合薄膜於25 ℃下進行滲透蒸發分離90 wt%異丙醇水溶液有最佳之分離效能，其透過量約為780 g/m2h而透過水濃度高於99 wt%。

關鍵字

聚醯胺 ； 可變單一能量慢速正子束 ； 滲透蒸發 ； 界面聚合

並列摘要

To improve the permeation rate of polyamide (PA) membrane, a series of polyamide thin-film composite (TFC) membranes was prepared via interfacial polymerization of various water-soluble amines (DMDPA, NTEA, DETA) and various acyl chloride monomers (DEMDC, PC, TMC) on the surface of asymmetric cellulose acetate (CA) membranes. The PA/CA composite membranes were applied to the pervaporation separation of aqueous alcohol solutions. Attenuated total reflection infrared spectroscopy (ATR-FTIR), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were used to characterize the chemical structures and morphologies of the polyamide active layers of the composite membranes. The affinity between the membrane and the feed solution was studied through contact angle measurement.
The effects of the chemical structure of the monomers and the interfacial polymerization conditions, such as the monomer concentration of aqueous and organic solutions, the immersion time of aqueous solution, the polymerization time and organic solvents, on the pervaporation performance were investigated. In addition, the effects of the operation conditions of the pervaporation separation process, such as the operating pressure, the composition, the operating temperature, and the kind of the feed solution, on the pervaporation performance were also studied. It was found that the different chemical structures of the monomers, which caused different reactivities and sterical stabilizations, dominated the chemical structures and cross-linking degrees of the polyamide active layers of the composite membranes. The desirable monomers for interfacial polymerization were the amine monomer DETA and the acyl chloride TMC.
From this study on the correlation between the chemical structure of polyamide layer and the pervaporation, it was found that the thickness of the polyamide active layer increased, the permeation rate decreased, and the water concentration in the permeate increased with a decrease in the viscosity of the organic solvent. To further understand the variation in the fine-structure of polyamide active layer of the composite membrane prepared via interfacial polymerization using different organic solvents, positron annihilation spectroscopy (PAS) coupled with a variable monoenergy slow positron beam (VMSPB) was utilized to detect the depth profile of the free volume and multilayer structure in the PA/CA composite membrane. The data obtained from PAS experiments were expected to correlate well with the pervaporation performance.
It was found that the DETA-TMC/CA thin-film composite membranes prepared by immersing CA into 0.5 wt% aqueous DETA solution for 10s and then contacting it with 0.5 wt% TMC in iso-pentane organic solution for 5s had the best pervaporation performance of 90 wt% aqueous iso-propanol solution at 25 ℃, which was the permeation rate was about 780 g/m2h and the water concentration in the permeate was high than 99 wt%.

並列關鍵字

VMSPB ； pervaporation ； interfacial polymerization ； polyamide

參考文獻

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