Song Chen, Rutledge Gregory C
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Langmuir. 2022 Feb 22;38(7):2301-2313. doi: 10.1021/acs.langmuir.1c03016. Epub 2022 Feb 7.
From an environmental perspective, microfiltration membranes are attractive for the separation of emulsified oils from contaminated water. However, fouling of the membrane is a major drawback of the technology. "Liquid-infused membranes" (LIMs) have the potential to eliminate membrane fouling. Here, we demonstrate the practical application of LIMs for the separation of oil from a stable oil-in-water emulsion and characterize their resistance to fouling. The base membrane is an electrospun nonwoven fibrous layer of the fluorinated copolymer poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP). The surface energy of the PVDF-co-HFP fibers was lowered by the covalent attachment of a fluorinated silane (PFOCTS), and then, the membrane was infused with a perfluoropolyether. The membrane was then challenged with model emulsions of dodecane in water in a cross-flow configuration. This PFOCTS-modified LIM showed better infused liquid stability, permeation selectivity, higher permeate flux than the unmodified LIM, and better anti-fouling properties than the bare membrane without infused liquid. We also examine the mechanism for transport of the dispersed oil phase through the liquid-infused membrane. We find a linear relationship between the dodecane flux and dodecane concentration in the feed and a higher dodecane flux through the PFOCTS-modified membrane than the unmodified one, which suggests that the capture of dodecane droplets from the feed plays an important role in determining the overall rate of permeation. Other factors such as lower viscosity of the infused liquid, larger pore size, and higher operating pressure also improved the permeate flux through the LIMs. Overall, this work provides some guidelines on the design of composite membranes comprising infused liquids and the choice of operating conditions for the filtration process.
从环境角度来看，微滤膜对于从受污染水中分离乳化油具有吸引力。然而，膜污染是该技术的一个主要缺点。“液体注入膜”（LIMs）有消除膜污染的潜力。在此，我们展示了LIMs在从稳定的水包油乳液中分离油的实际应用，并表征了它们的抗污染性能。基膜是由氟化共聚物聚（偏二氟乙烯 - 共 - 六氟丙烯）（PVDF - co - HFP）制成的电纺非织造纤维层。通过氟化硅烷（PFOCTS）的共价连接降低了PVDF - co - HFP纤维的表面能，然后向膜中注入全氟聚醚。然后，在错流配置下用十二烷在水中的模型乳液对该膜进行测试。这种经PFOCTS改性的LIM显示出比未改性的LIM更好的注入液体稳定性、渗透选择性、更高的渗透通量，并且比没有注入液体的裸膜具有更好的抗污染性能。我们还研究了分散油相通过液体注入膜的传输机制。我们发现十二烷通量与进料中十二烷浓度之间存在线性关系，并且通过PFOCTS改性膜的十二烷通量高于未改性膜，这表明从进料中捕获十二烷液滴在决定整体渗透速率中起重要作用。其他因素，如注入液体的较低粘度、较大孔径和较高操作压力，也提高了通过LIMs的渗透通量。总体而言，这项工作为包含注入液体的复合膜设计以及过滤过程操作条件的选择提供了一些指导方针。
