本研究是利用實驗室合成的聚偏二氟乙烯(Polyvinylidene fluoride, PVDF)平板式薄膜，來組裝模組進行直接接觸式薄膜蒸餾(Direct Contact Membrane Distillation, DCMD) 與真空式薄膜蒸餾(Vacuum Membrane Distillation, VMD)用於海水淡化之效能探討，進料之模擬海水為3.5 wt%的NaCl水溶液。合成薄膜的組成為PVDF、磷酸三乙酯(Triethyl phosphate, TEP)及Tween-20的混合溶液，將改變沉澱槽之組成成分以製備不同結構之薄膜，探討其薄膜結構對蒸餾操作之影響。 在實驗操作部分主要是探討不同的參數對薄膜蒸餾之滲透通量及鹽阻隔率之影響，DCMD中兩側流體流動是逆流方式，而在VMD操作中滲透側保持在5.33 kPa，其它參數包括在進料溫度(50~70 oC)、進料速度(0.3~0.7 L/min)與不同進料濃度(純水~15wt%NaCl溶液)。 在DCMD與VMD中其結果顯示隨著沉澱槽TEP wt%的比例增加，所製成的薄膜之通量皆會高於沒改質的薄膜，是由於隨著TEP在沉澱槽的比例增加薄膜表面皮層結構不易形成，且大孔洞數變多。且提高進料溫度能明顯增加滲透通量，但極化現象也較嚴重，而增加進料流率則對於滲透通量之提升較不顯著，但對於高溫進料操作之溫度極化現象具有較明顯改善效果。 The synthesized poly(vinylidene fluoride) (PVDF) flat-sheet membrane was used in the Direct Contact Membrane Distillation (DCMD) and Vacuum Membrane Distillation (VMD) for desalination, and the performances of the membrane distillation system were studied. The simulated seawater of 3.5 wt% NaCl solution was adepted as the feed. The dope solution of PVDF, Triethyl phosphate(TEP) and Tween-20, and the flat membranes were prepared by varying the concentration of TEP in the coagulation bath. The membrane structures were observed by the SEM analysis. The performances of DCMD and VMD were measured under various operating parameters included feed temperature (50~70oC), feed flow rate (0.3~0.7 L/min) and feed concentration (0~15wt% NaCl). In DCMD and VMD the experimental results showed the higher flux performance than original membranes which prepared by higher weigh percent of TEP solution, and membrane have large pore size in the top surface is increasing the weight percent of TEP in coagulant bath. And increasing the temperature of the feed can significantly increase the flux, but the polarization phenomena become more serious, increasing feed flow rate the effect is not obvious on the flux, but the temperature polarization phenomenon can be reduced by the feed flow rate as the high feed temperature.
