Abstract In order to mitigate the harm of solvent volatilization during thermally induced phase separation (TIPS), more and more green solvents/diluents were developed, produced and applied in the membrane field. In this paper, trioctyl trimellitate (TOTM), an environmentally friendly diluent with high boiling point and low vapor pressure, was firstly introduced to prepare porous membranes, especially hydrophobic poly(ethylene-chlorotrifluoroethylene) (ECTFE) membranes by TIPS. Effects of ECTFE content on the membrane properties, including morphology, pore size distribution, porosity, liquid entry pressure of water (LEPw), water contact angle (WCA) and mechanical properties were characterized. Then the prepared ECTFE membranes were tested in vacuum membrane distillation (VMD). Phase diagram of this new ECTFE/TOTM binary system presented the existence of liquid-liquid (L-L) phase separation region when the ECTFE content was below 40%. The characterization results showed that the 15 wt% ECTFE membranes presented the continuous structure without the production of dense layer, but as the further increasing of polymer content, the spherulite structure began to be observed and surface became denser. Significantly, all the prepared ECTFE membranes exhibited excellent hydrophobicity. The liquid entry pressure of water (LEPw) and water contact angle (WCA) of 20 wt% ECTFE membranes reached 0.42 MPa and 139.9°, respectively. Moreover, in VMD, the prepared membranes exhibited high permeability (permeation flux was 23.09 kg/(m2.h)) and separation (salt rejection was 99.9%) performance. The above results show that the prepared ECTFE membrane showed promising stability performance in long-term operation of VMD for concentration of salt solution.

中文翻译：

---

用绿色稀释剂 TOTM 制备 ECTFE 多孔膜及其在 VMD 工艺中的性能

摘要 为了减轻热致相分离（TIPS）过程中溶剂挥发的危害，越来越多的绿色溶剂/稀释剂被开发、生产并应用于膜领域。本文首次引入高沸点、低蒸气压的环保稀释剂偏苯三酸三辛酯（TOTM）制备多孔膜，特别是TIPS制备疏水性聚（乙烯-三氟氯乙烯）（ECTFE）膜。表征了 ECTFE 含量对膜性能的影响，包括形态、孔径分布、孔隙率、水的液体进入压力 (LEPw)、水接触角 (WCA) 和机械性能。然后在真空膜蒸馏 (VMD) 中测试制备的 ECTFE 膜。这种新的 ECTFE/TOTM 二元系统的相图显示了当 ECTFE 含量低于 40% 时存在液-液 (LL) 相分离区域。表征结果表明，15 wt% ECTFE膜呈现连续结构，没有产生致密层，但随着聚合物含量的进一步增加，开始观察到球晶结构，表面变得更致密。值得注意的是，所有制备的 ECTFE 膜都表现出优异的疏水性。20 wt% ECTFE 膜的水的液体进入压力 (LEPw) 和水接触角 (WCA) 分别达到 0.42 MPa 和 139.9°。此外，在 VMD 中，制备的膜表现出高渗透性（渗透通量为 23.09 kg/(m2.h)）和分离（脱盐率为 99.9%）性能。