Abstract:

Membrane distillation processes are less affected by water with high salinity, including high saline water from mines. However, membrane scaling and wetting have restricted their industrial applications. In this work, we compared two types of commercial flat hydrophobic membranes, i.e., polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), with their composite membranes. The composite membranes were prepared with hydrophilic and hydrophobic surface modification, namely PVA-PAA/PTFE and Teflon/PVDF. The effects of membrane scaling and wetting on the prepared membranes were systematically investigated using the concentrated saturated calcium sulfate (CaSO₄) solution in direct contact membrane distillation (DCMD). We analyzed their membrane scaling and wetting mechanisms and presented their potential application and optimal membrane structure for high-saline mine water. Our experimental results indicated that the scaling on the membrane surface was the main influencing factor in the concentration process of the CaSO₄ solution in DCMD. Although the microstructures of the bare and modified membranes differed, their anti-scaling abilities were similar. Compared to the other prepared membranes, the Teflon/PVDF composite membrane exhibited superior anti-scaling performance given its slip characteristics. On the other hand, the PVA-PAA/PTFE composite membrane exhibited marginal improvement in anti-scaling ability despite its dense hydrophilic surface.

Key words: high-saline mine water, membrane distillation, hydrophilic surface modification, hydrophobic surface modification, scaling, wetting

摘要：

膜蒸馏过程受料液盐度的影响较小，可以处理高矿化度的矿井水，但膜污染和润湿制约其工业化应用。本文首次全面比较了两种商业化的疏水膜，即平板聚四氟乙烯（PTFE）和聚偏氟乙烯（PVDF），以及分别进行亲水和疏水表面改性后制备的PVA-PAA/PTFE和Teflon/PVDF两种复合膜，在直接接触式膜蒸馏（DCMD）中浓缩饱和硫酸钙溶液时的结垢和润湿程度。重点分析了两种基膜和复合膜的结垢和润湿机理，探讨它们在矿井水浓缩中的应用潜力和最佳膜结构。实验结果显示，饱和硫酸钙浓缩过程中，膜表面结垢是主要影响因素，PTFE膜和PVDF膜尽管膜微观结构差别巨大，但抗结垢能力接近；Teflon/PVDF复合膜因其表面有滑移特性而表现出完美的抗结垢性能，PVA-PAA/PTFE复合膜尽管有致密的亲水表面，抗结垢能力并不强。

关键词: 矿井水, 膜蒸馏, 亲水改性, 疏水改性, 结垢, 润湿