Facile and scalable surface functionalization approach with small silane molecules for oil/water separation and demulsification of surfactant/asphaltenes-stabilized emulsions

Abstract

Oil contaminations have been challenging issues in a wide range of engineering and environmental fields. Herein, we employ a small silane molecule, γ-mercaptopropyldi(trimethylsiloxy)methylsilane (MD(SH)M), to functionalize fiber-based substrates (i.e., stainless steel mesh, cotton fiber) for oil decontamination processes including oil–water separation, oil absorption and demulsification. The functionalized stainless-steel mesh (SSM@PM) can completely separate water and oils of high/low density without prewetting by oil. The functionalized cotton fibers (CF@PM) can absorb different oils from water without being wetted by water and maintain excellent oil absorption performance even after 10 cyclic reuses. Besides, CF@PM shows good demulsification performance to water-in-oil emulsions stabilized by span 80 and asphaltenes. The underlying interaction mechanisms are investigated using force measurements. The CF@PM shows much stronger repulsion to water droplets in air as compared to unmodified cotton fiber, and SSM@PM has strong attraction to oil droplets under water but almost no attraction to water droplets in oil, accounting for the effective oil/water separation capacity. Such strong attraction between oil and MD(SH)H-modified surfaces can be attributed to the hydrophobic interaction as confirmed by surface force measurements. This work provides a facile surface functionalization approach with great potential applications in oil/water separation and demulsification of surfactant- or asphaltenes-stabilized emulsions.