Underwater superoleophobic GO-PEI-SiO2-Hal quaternary sphere-rod nacre-inspired mesh by LBL self-assembly for high-efficiency oil-water separation

The easy preparation of robust superwetting materials for oily wastewater disposal still remains a challenge. Inspired by the self-cleaning and mechanical properties of natural nacre underwater, herein, we have successfully developed sphere-rod quaternary artificial nacre-inspired meshes (named GO-PEI-SiO ₂ -Hal) via interfacial self-assembly using 2D graphene oxide nanosheets, hyperbranched polyethyleneimine, SiO ₂ nanospheres, and hollow halloysite nanotubes (Hal) as the building blocks. The nacre-like “brick-and-mortar” layered microstructure was successfully formed and tightly coated to the mesh, showing excellent mechanical properties with Young`s modulus up to 19.7 ± 2.6 GPa. Compared to the ternary structures, the quaternary sphere-rod morphology improved the surface roughness, and these four organic/inorganic building blocks are all hydrophilic, which together resulted in the superhydrophilic and underwater superoleophobic characteristics. The effects of building block concentration, dipping number, and mesh size on wettability and oil-water separation performance were studied in detail. The optimal (GO-PEI-SiO ₂-Hal-1) ₁₅@Fe ₃₀₀ mesh showed an underwater oil contact angle of 159 ^o for 1,2-dichloroethane, low oil adhesion, and excellent separation efficiency up to 99.8% at an ultrahigh flux up to 195,038 L m ⁻² h ⁻¹ . This nacre-like mesh exhibited excellent salt tolerance, acid-alkali resistance, recycling ability, and mechanical properties for practical oily wastewater treatment.