本研究主要探討聚偏二氟乙烯poly vinylidene fluoride(PVDF)平板式薄膜及中空纖維膜之製備、電漿改質及其在薄膜蒸餾技術方面的運用。首先利用濕式相轉換法製備非對稱PVDF 薄膜，溶劑為NMP，非溶劑為水；藉由改變製膜液與沈澱槽之組成，製作出一系列不同孔隙結構之薄膜。其次，利用低溫電漿(N2/H2)改質膜材，探討電漿處理時間、電漿功率、薄膜孔隙結構等參數對接枝量的影響，並以SEM、 DSC、XRD、Contact Angle 等來作膜材物性分析各種改質條件的膜表面性質，再利用直接接觸薄膜蒸餾法（direct contact membrane distillation，DCMD）以及空氣間隙薄膜蒸餾法(air-gap membrane distillation，AGMD)針對模擬鹽水與真實海水作淡化實驗，測試去鹽效率與通量。研究操作變數包括：冷熱端溫度變化、熱端流速變化及微溫差對透過率與拒鹽率之影響，預期有效應用於海水淡化及含鹽廢水回收技術，達到節省能源的目標並得到飲用水標準之滲透水質。計畫第二年將以PVDF/NMP溶液以濕式紡絲法進行中空纖維膜製備，以延遲成膜法進行滲透蒸發中空纖維膜皮層結構之最佳化，並利用溶劑水溶液為芯液，降低內表面相分離速率，增加內表面孔隙度，達到多孔性PVDF中空纖維膜結構製備出最適合薄膜蒸餾技術之中空纖維膜，並製成管狀模組以AGMD與VMD測試薄膜蒸餾去鹽效率與通量測試，及其長期穩定性的影響。 This research investigate the preparation, modification, and application in the membrane distillation of porous poly(vinylidene fluoride) (PVDF) membranes. PVDF membranes with different porous structures were prepared by immersion-precipitation of a casting solution in coagulation baths composed of NMP and water (nonsolvent). SEM, DSC, XRD, and Contact Angle analyzer were used to characterize the membranes. To enhance MD flux, PVDF flat-sheet membranes were treated by plasma in this study, and they were used for the AGMD and DCMD experiments, which tested flux and salt reduction rate through the membrane and measured how thick the layer that was plasma treated by observing the penetration length traversed by a color agent through the membrane. In regard to the energy savings as a result of the plasma treatment, this research discussed the effect of little temperature difference. Also, the effects of temperature and pressure gradient and air-gap distance on the MD membrane performance for purifying drinking water were investigated. In the second year of the project, PVDF hollow fiber membrane was spun via dry-wet spinning method to eliminate the outer dense skin layer by vapor induced phase separation (VIPS). In addition, aqueous solvent solution was used as the bore liquid to increase inner surface porosity. So that it could achieve the objective of porous morphology design. In addition, DCMD and VMD with tubular modules was also studied theoretically and experimentally.
