PVDF-co-HFP管狀薄膜應用於乙酸乙酯水溶液濃縮之研究

Study on the concentration of ethyl acetate aqueous solution of PVDF-co-HFP tubular membrane

陳仕明(Shr-Ming Chen)

指導教授 ： 李魁然

中原大學/工學院/化學工程研究所/碩士(2013年)

https://doi.org/10.6840/cycu201300998

摘要

本研究不同於傳統方式製備一管狀薄膜，係將Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP)塗佈於聚酯管狀基材之上，並進行乙酸乙酯水溶液之脫乙酸乙酯滲透蒸發程序。研究中除了探討PVDF-co-HFP高分子濃度對滲透蒸發效能之變化，亦探討滲透蒸發操作條件對分離效能的影響。
實驗結果發現，當PVDF-co-HFP高分子濃度為20wt%時具有較佳的分離效能，於操作溫度30℃與進料5wt%以酸乙酯水溶液下，其透過量為1034 g/m2h、透過端乙酸乙酯濃度為84.9wt%。這是由於在此高分子濃度之下，PVDF-co-HFP管膜具有適當的機械強度以應用於滲透蒸發分離程序。此外，亦發現滲透蒸發分離效能會隨著進料端乙酸乙酯的濃度增加而有所提昇。由於在較高乙酸乙酯進料濃度之下，PVDF-co-HFP高分子的膨潤程度上升，因此透過量得以提昇；此外，由於PVDF-co-HFP與乙酸乙酯之間具有較好的親和性，因此在進行滲透蒸發分離程序時，PVDF-co-HFP當中的HFP基團易翻轉至管膜表面，進而提昇選擇性。
為了進一步提昇滲透蒸發效能，研究中採用雙凝聚劑的方式製備PVDF-co-HFP管膜，分別以正丁醇與水為凝聚劑。結果發現PVDF-co-HFP鑄膜液的相分離速率因此下降，使得PVDF-co-HFP管膜的表面粗糙度與孔隙度得以上升，因此透過量大幅提昇，且不喪失選擇性。以此方式所製備之PVDF-co-HFP管膜，在操作溫度為30℃、乙酸乙酯進料為5wt%之下，具有最佳之滲透蒸發效能，其透過量與透過端乙酸乙酯濃度分別為1548 g/m2h與93.3wt%。

關鍵字

濃縮 ； 滲透蒸發 ； 偏二氟乙烯- 共-六氟丙烯 ； 管狀薄膜 ； 乙酸乙酯

並列摘要

This study differs from the traditional preparation of tubular membranes. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) was cast on a PET tubular substrate, which was used to remove ethyl acetate (EA) from EA aqueous solutions by pervaporation. Apart from investigating the polymer concentration effect on the pervaporation performance, this study also investigated the effect of the pervaporation operating conditions on the separation efficiency.
From experimental results, we found that the separation efficiency was better when the PVDF-co-HFP polymer concentration was 20 wt%; the permeation flux was 1034 g/m2h, and the ethyl acetate concentration was 84.9 wt%. This was because the PVDF-co-HFP tubular membrane had appropriate mechanical strength for pervaporation applications. Moreover, we found that the pervaporation performance was improved with increasing feed ethyl acetate concentration. Since at higher ethyl acetate concentration, the degree of swelling of the PVDF-co-HFP polymer increases, and therefore, the permeation flux can be improved. In addition, the PVDF-co-HFP has good affinity with ethyl acetate; thus, the HFP group of PVDF-co-HFP easily turns over to the tubular membrane surface, enhancing the selectivity during the pervaporation process.
To further improve the pervaporation performance, we applied for this study a dual coagulate method to prepare PVDF-co-HFP tubular membranes, with n-butanol and water as coagulants. It was found that the PVDF-co-HFP dope solution phase separation rate decreased. As a result, the PVDF-co-HFP tubular membrane surface roughness and porosity increased; therefore, the permeation flux was significantly improved, without loss of the selectivity. The PVDF-co-HFP tubular membrane tested for a feed concentration of 5 wt% ethyl acetate aqueous solution and at an operating temperature of 30C showed the best pervaporation performance, with a permeation flux of 1548g/m2h and a 93.3 wt% ethyl acetate in the permeate.

並列關鍵字

tubular membrane ； PVDF-co-HPF ； ethyl acetate ； pervaporation ； concentration

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