近年來，由於世界各國的人口急遽增加及經濟的快速成長，水的需求日漸增加，開發新水源已是一個世界性的重要問題，有鑑於此，本文將以薄膜蒸餾法（membrane distillation, MD）來做為海水淡化的另一種選擇。而所謂的薄膜蒸餾就是兩種不同的溶液在不同的溫度下，被一多孔且疏水性的薄膜分隔，因薄膜兩側溶液溫度的差異，相對地產生不同的蒸氣壓力，由於這個壓力差所產生驅動力，使得高溫液體的水分子在薄膜的一端蒸發，經過薄膜，然後在另一側凝結，稱之為薄膜蒸餾。在薄膜蒸餾法中，本研究是以直接接觸式薄膜蒸餾（direct contact membrane distillation, DCMD）與空氣間隙式薄膜蒸餾（air gap membrane distillation, AGMD）為主題進行海水淡化之製備，由實驗結果得知，進料端溫度固定下，其滲透端溫度與滲透通量呈現出線性關係，滲透通量隨著進料端溫度提升而增加，但滲透通量會與滲透端溫度的提升而下降，而薄膜會依厚度的增加而使滲透通量降低，但選擇性及鹽去除率皆會提升，而厚度以0.025 mm之聚四氟乙烯（polytetrafluoroethylene, PTFE）薄膜為最佳選擇。電漿改質方面，以改質面朝進料端之各項數值皆比改質前更好，而改質面若朝滲透端反而使各項數值降低。在模組方面以DCMD模組的滲透通量優於AGMD模組，而DCMD模組三又優於DCMD模組二。 Membrane distillation (MD) is a relatively new separation process which is being investigated worldwide as a low cost, energy saving alternative to other conventional separation processes. Plasma-modified polytetrafluoroethylene (PTFE) membranes for use in membrane distillation were prepared with composite PTFE membranes. The composite membrane consisted of a porous woven support and a dense PTFE layer. The membranes were characterized using contact angle measurement. Finally, the plasma-modified membranes were tested for their performance in the process of desalination by means of the air gap membrane distillation (AGMD) and direct contact membrane distillation (DCMD). It was found that the plasma treatment strongly affected the surface hydrophilicity of the modified membranes and thus enhanced their desalination performance. It was also found that prolonging the plasma treatment time and increasing the plasma power significantly decreased the water contact angle and significantly changed the surface morphology of the modified membranes. Furthermore, the plasma treatment only slightly changed the roughness and surface porosity. Such changes in the surface’s morphology and polarity enhanced the hydrophilicity of the modified membranes and then significantly improved the permeation flux but expectedly decreased the salt rejection.
