Abstract
Separating oil-water mixtures is critical in a variety of practical applications, including the treatment of industrial wastewater, oil spill cleanups, as well as the purification of petroleum products. Among various methodologies that have been utilized, membranes are the most attractive technology for separating oil-water emulsions. In recent years, selective wettability membranes have attracted particular attention for oil-water separations. The membrane surfaces with hydrophilic and in-air oleophobic wettability have demonstrated enhanced effectiveness for oil-water separations in comparison with underwater oleophobic membranes. However, developing a hydrophilic and in-air oleophobic surface for a membrane is not a trivial task. The coating delamination process is a critical challenge when applying these membranes for separations. Inspired by the above, in this study we utilize poly(ethylene glycol)diacrylate (PEGDA) and 1H,1H,2H,2H-heptadecafluorodecyl acrylate (F-acrylate) to fabricate a hydrophilic and in-air oleophobic coating on a filter. We utilize methacryloxypropyl trimethoxysilane (MEMO) as an adhesion promoter to enhance the adhesion of the coating to the filter. The filter demonstrates robust oil repellency preventing oil adhesion and oil fouling. Utilizing the filter, gravity-driven and continuous separations of surfactant-stabilized oil-water emulsions are demonstrated. Finally, we demonstrate that the filter can be reused multiple times upon rinsing for further oil-water separations.
Highlights
Oil-water separation is a crucial step in a wide variety of industries [1,2]
The filters were irradiated by a long-wavelength ultraviolet (UV) light, which resulted in the grafting of F-poly(ethylene glycol)diacrylate (PEGDA) to the methacryloxypropyl trimethoxysilane (MEMO)-treated filter surface (Figure 1a and Section S1)
The results showed that the adhesion force values were nearly constant (≈1.32 μN ± 0.10 μN) on filters with an inherent nominal pore size of 6.0 μm, which were coated with F-PEGDA, irrespective of the F-acrylate composition
Summary
Oil-water separation is a crucial step in a wide variety of industries [1,2]. For example, 140,000 L of oil-contaminated water is produced during conventional mining operations on a daily basis [3]. Hydrophilic and in-air oleophobic (i.e., oil contact angle, θ oil > 90◦ ) membranes can overcome this limitation by providing oil repellency, underwater, and in the air [20,40] This enables them to exhibit unique features in oil-water separations. T = 22 ◦ C) is higher than that of oils (γlv = 20–30 mN m−1 , T = 22 ◦ C), a large volume of reports [9,41,42,43,44,45,46] have utilized materials composed of a low surface energy component along with a hydrogen-bond-capable hydrophilic moiety as the membrane coating to achieve selective wettability for water over oil [20,47,48,49,50,51] For example, Brown et al [52]. We demonstrate that the filter can be reused multiple times upon cleansing for further oil-water separations
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