Durable superhydrophobic coating based on halloysite nanotubes for versatile oil/water separation and reusable water collection

Fog water collection gains increasing attention for harvesting atmospheric water to solve the water resource crisis in arid or semi-arid areas. In this work, a durable superhydrophobic coating based on halloysite nanotubes (HNT) for water collection is fabricated by introducing 1H,1H,2H,2H-perfluorodecyl trimethoxysilane (PFTS) modified HNT into a hydrophobic polydimethylsiloxane (PDMS) coating to construct a rough and superhydrophobic surface. The dip-coating method is employed to apply the coatings onto various substrates. The surface wettability, water collection rate, mechanical stability, and durability, oil/water separation efficiency and flux, and oil absorption capacity are investigated in detail. When the content of fluorinated modified HNT (F-HNT) is 15%, superhydrophobic F-HNT@PDMS coated fabrics with a high water contact angle (157.3°) as well as a low sliding angle (3.7°) are obtained, and the treated fabrics show excellent self-cleaning ability. After 100 mechanical wear cycles, the coated fabrics remain superhydrophobicity, and the oil/water separation efficiency is maintained above 99.5%. Furthermore, different substrates dip-coated with F-HNT@PDMS exhibit high-efficiency water collection rates of 952.25-1058.5 mg∙cm−2∙h−1. Therefore, this work provides a feasible strategy for preparing a durable superhydrophobic coating with a high-efficiency water collection rate and is expected to be applied in fog water harvesting in scarce areas.