Abstract Membrane distillation (MD) is a promising desalination process especially in small scale systems. However, the lack of commercial MD membranes severely impedes the industrialization. Although various approaches have been explored to develop high-performance membranes, the complicated processing procedures and high cost are two major obstacles to scale up the available membranes. In this study, a facile bottom-up method using water as coagulation bath was proposed to fabricate porous poly(vinylidene fluoride) (PVDF) membranes for direct contact membrane distillation (DCMD) in view of application in desalination. By covering a piece of non-woven substrate on the nascent film followed by immersion into a water bath, a skinless PVDF membrane with an isotropic structure was obtained. The SEM characterization confirmed the formation of a rough top surface and sponge-like granular membranes composed of spherulites. The water contact angles substantially increased from 71.7° for PVDF-N membrane to ca. 144° for bottom-up membranes. The DCMD flux of the bottom-up PVDF membrane was as high as 41.4 kg/(m2 h) with a polymer concentration of 15 wt%, when the feed and permeate temperatures were 70 °C and 20 °C, respectively. This facile, environmentally friendly approach provides the possibility of manufacturing large-scale high-performance MD membranes.

中文翻译：

---

用于直接接触膜蒸馏 (DCMD) 的各向同性聚偏二氟乙烯膜的一步制造

摘要 膜蒸馏 (MD) 是一种很有前途的脱盐工艺，尤其是在小规模系统中。然而，商业MD膜的缺乏严重阻碍了工业化。尽管已经探索了各种方法来开发高性能膜，但复杂的加工程序和高成本是扩大可用膜的两个主要障碍。在这项研究中，鉴于在海水淡化中的应用，提出了一种使用水作为凝固浴的简便自下而上的方法来制造用于直接接触膜蒸馏 (DCMD) 的多孔聚偏二氟乙烯 (PVDF) 膜。通过在新生薄膜上覆盖一块无纺布基材，然后浸入水浴中，获得了具有各向同性结构的无表皮 PVDF 膜。SEM 表征证实形成了粗糙的顶面和由球晶组成的海绵状颗粒膜。水接触角从 PVDF-N 膜的 71.7° 大幅增加到大约 144° 用于自下而上的膜。当进料温度和渗透温度分别为 70 °C 和 20 °C 时，自底向上 PVDF 膜的 DCMD 通量高达 41.4 kg/(m2 h)，聚合物浓度为 15 wt%。这种简便、环保的方法为制造大规模高性能 MD 膜提供了可能。当进料和渗透温度分别为 70 °C 和 20 °C 时，4 kg/(m2 h) 聚合物浓度为 15 wt%。这种简便、环保的方法为制造大规模高性能 MD 膜提供了可能。当进料和渗透温度分别为 70 °C 和 20 °C 时，4 kg/(m2 h) 聚合物浓度为 15 wt%。这种简便、环保的方法为制造大规模高性能 MD 膜提供了可能。