Utilizing a layer-by-layer self-assembly strategy to construct eco-friendly and sustainable superhydrophobic C–S@PDMS@SiO2 coatings on engineering materials for efficient oil-water separation

In order to mitigate the economic and environmental damage caused by the industrial discharge of oily wastewater, the research and development of efficient and long-lasting oil-water separation devices is imminent. Among them, utilizing the copper stearate (C-S) and hydrophobic SiO2 nanoparticles, a robust superhydrophobic and superoleophilic C-S@PDMS@SiO2 (PDMS shortened form polydimethylsiloxane) was prepared on stainless steel mesh (SSM) using layer-by-layer assembly for heavy oil/water separation. The resulting superhydrophobic surface has a water contact angle of 158° and a water rolling angle of less than 3°. The separation efficiency is as high as 99.78% and a flux is greater than 20,000 L/(m2×h) after 10 separation cycles for a variety of heavy oil/water mixtures. The superhydrophobic performance of C-S@PDMS@SiO2 SSM is superior to that of the C-S SSM as the modified hydrophobic SiO2 nanoparticles are grafted with long-chain PDMS. The C-S@PDMS@SiO2 SSM exhibited good mechanical and chemical stability. Even under corrosive solution environments (e.g., strong acids, strong bases, and high salt solutions), it was able to separate a variety of immiscible heavy oil/water mixtures with a separation efficiency of greater than 96.5%. In addition, the prepared separation membranes were able to maintain high hydrophobicity after 20 abrasion cycles with 1000 grit sandpaper and still had high separation efficiency. This type of heavy oil/water separation device has a simple preparation process, a sturdy structure, low cost, environmental friendliness, high separation efficiency, and good mechanical and chemical stability, providing a new scheme for the development and wide application.