The construction of rough and porous hydrophobic membrane surface is expected to overcome the obstacles including low permeate water flux and membrane pore wetting which greatly restrict the development of membrane distillation (MD) technology. In this study, a rough and porous polytetrafluoroethylene (PTFE) powder-embedded polyvinylidene fluoride (PVDF) hydrophobic coating layer was compounded on the outer surface of PVDF hollow fiber support membrane by the dilute solution coating-phase inversion method. PVDF hollow fiber support membrane was fabricated by the dry-jet wet-spinning technique. PTFE powder was directly incorporated in PVDF dilute coating solution and embedded in the porous PVDF coating layer after the nonsolvent induced phase separation (NIPS). The variations of membrane morphology, surface chemical compositions, hydrophobicity and wetting resistance were investigated by scanning electron microscope (SEM), Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), dynamic water contact angle (WCA) and liquid entry pressure (LEP) analysis. Membrane separation performance including desalination and ionic dyes removal properties was evaluated by VMD experiment. Compared with PVDF hollow fiber support membrane, both the surface hydrophobicity and the water permeability of the PTFE powder-embedded PVDF hollow fiber composite membrane (HFC) had obvious improvement. The surface WCA and permeate water flux increased from 92.6° and 11.3 kg/m^2.h for PVDF support membrane to 133.6° and 26.8 kg/m^2.h for the PTFE powder-embedded HFC membrane meanwhile NaCl rejection can be maintained above 99.9% (3.5 wt% NaCl aqueous solution at 50 °C and permeate pressure at 31.3 kPa). The separation performance of HFC membrane can remain stable without obvious pore wetting during the continuous MD operation for 36 h. Different from the desalination, porous hollow fiber membrane would adsorb two different charged dyes, Congo red (CR) and methylene blue (MB) to a certain extent, resulting in the decrease of membrane flux and the change of permeate water quality. Finally, the MD separation mechanism of inorganic salt, anionic dye and cationic dye by PTFE powder-embedded HFC membrane was proposed.

粗糙多孔疏水膜表面的构建有望克服低渗透水通量和膜孔润湿等障碍，这些障碍极大地限制了膜蒸馏（MD）技术的发展。本研究采用稀溶液涂布-相转化法在PVDF中空纤维支撑膜外表面复合一层粗糙多孔的聚四氟乙烯（PTFE）粉末包埋聚偏二氟乙烯（PVDF）疏水涂层。PVDF中空纤维支撑膜采用干喷湿纺技术制备。PTFE 粉末直接掺入 PVDF 稀释涂层溶液中，并在非溶剂诱导相分离 (NIPS) 后嵌入多孔 PVDF 涂层中。膜形态、表面化学成分的变化，LEP ) 分析。通过VMD实验评估了包括脱盐和离子染料去除性能在内的膜分离性能。与PVDF中空纤维支撑膜相比，PTFE粉末包埋的PVDF中空纤维复合膜（HFC）的表面疏水性和透水性都有明显的提高。表面 WCA 和渗透水通量从PVDF 支撑膜的92.6° 和 11.3 kg/m ^{2. h 增加到 133.6° 和 26.8 kg/m 2。}h 对于 PTFE 粉末包埋的 HFC 膜，同时 NaCl 截留率可以保持在 99.9% 以上（3.5 wt% NaCl 水溶液在 50 °C 和渗透压力在 31.3 kPa）。在连续 MD 运行 36 h 期间，HFC 膜的分离性能可以保持稳定，没有明显的孔润湿。与脱盐不同，多孔中空纤维膜会在一定程度上吸附刚果红（CR）和亚甲蓝（MB）两种不同的带电染料，导致膜通量降低，产水水质发生变化。最后提出了PTFE粉末包埋HFC膜对无机盐、阴离子染料和阳离子染料的MD分离机理。