Durable tetra-scale superhydrophobic coatings with virus-like nanoparticles for oil–water separations

Highlights: • Coating of virus-like silica nanoparticles produced the superhydrophobic surfaces. • Superhydrophobicity was substantially improved due to the spikes on the VLSN. • The tetra-scale membranes were efficient separators for water–oil mixtures (>99%). • High contact angle was kept after 600 cycles of washing durability test. • The superhydrophobic fabric membranes absorbed oil rapidly from water. For highly efficient water–oil separation, superhydrophobic surfaces were prepared by coating the virus-like silica nanoparticles (VLSNs) on a substrate in scalable manner and subsequent fluoroalkyl silane through the sol–gel process. On the VLSN-coated glass substrate, the contact angle of the water droplet increased from 100.8° (plain silica nanoparticles) to 178.9° in the air as the areal density of coated nanoparticles increased up to 8,170 nanoparticles per µm². Furthermore, fabric membrane and stainless-steel mesh were coated with VLSNs and subsequently functionalized with fluoroalkyl silane, which was utilized for continuous oil–water separation with a high separation efficiency (>99%), high flux (>2,000 L/m²⋅h) and high washing durability (>500 cycles). Additionally, these superhydrophobic fabrics were applied for removing oil contaminants on water by absorption within ten seconds.