滲透蒸發輸送機制之探討

Abstract

本研究探討三種膨潤性質不同的 膜材在滲透蒸發(pervaporation)、蒸 氣透過(vapor permeation)及液體透 過(liquid permeation)三種程序中的 輸送行為。所採用的進料液體為不同 組成的乙醇-水溶液，所用的膜材有 TPX [poly(4-methyl-1-pentene)]、PU (polyurethane)及Nylon-4 。滲透蒸發 之結果顯示：乙醇的permeability 會 隨進料組成改變而變化，其行為與膜 材的膨潤行為完全一致; 水的 permeability 除會受膜材膨潤行為的 影響外，亦會受水分子clustering 效 應的影響。蒸氣透過及液體透過之實 驗結果亦顯示必需同時考量膜材的 膨潤效應及水的clustering 效應方能 解釋蒸氣及液體透過薄膜之行為。此 外，結果亦顯示：在滲透蒸發過程 中，進料是以蒸氣方式透過TPX 膜， 而在PU 膜及Nylon-4 膜中，會有液 態區及氣態區的存在。研究中亦進行 染色實驗，嘗試證明上述的滲透蒸發機制。

The present research explores the permeation behavior of ethanol and water through membranes in pervaporation, vapor permeation, and liquid permeation. The materials used to prepare the membranes are TPX, polyurethane, and Nylon-4, possessing different swelling characteristics in ethanol-water solution. The results of pervaporation reveal that the permeability of ethanol through the membranes is strongly dependent on the ethanol concentration in the feed. The dependence can be well explained by the swelling characteristics of the three membranes. However, to account for the behavior of water permeability, clustering effect of water should also be considered besides swelling characteristics. The data from vapor and liquid permeation also indicate that both swelling characteristics and water clustering should be taken into account to describe the transport of ethanol and water in membranes. In addition, the data suggest that, for TPX membranes, the feed penetrates the membrane in vapor form during pervaporation, and for PU and Nylon-4 membranes, both liquid and vapor zones can be found in membranes during pervaporation. Staining experiments were performed to provide direct evidence for the proposed mechanism above.