Magnetic, Durable, and Superhydrophobic Polyurethane@Fe₃O₄@SiO₂@Fluoropolymer Sponges for Selective Oil Absorption and Oil/Water Separation

TLDR

The authors fabricated magnetic, durable, superhydrophobic polyurethane sponges by first binding Fe₃O₄ nanoparticles to the sponge via chemical vapor deposition of tetraethoxysilane, then dip‑coating with a fluoropolymer, and characterized the resulting structure and the influence of TEOS CVD time and fluoropolymer concentration on wettability, mechanical strength, oil absorbency, and oil/water selectivity. The PU@Fe₃O₄@SiO₂@FP sponges exhibit rapid magnetic responsiveness, superhydrophobicity (water contact angle 157°) and superoleophilicity, high oil/water separation efficiency, can be magnetically driven to absorb floating and submerged oils, serve as membranes for continuous large‑scale oil removal, and retain superhydrophobicity and mechanical stability even under 200 % strain or 50 % compression with repeated reuse.

Abstract

Magnetic, durable, and superhydrophobic polyurethane (PU) sponges were fabricated by chemical vapor deposition (CVD) of tetraethoxysilane (TEOS) to bind the Fe3O4 nanoparticles tightly on the sponge and then dip-coating in a fluoropolymer (FP) aqueous solution. The sponges were characterized using scanning electron microscopy and other analytical techniques. The effects of CVD time of TEOS and FP concentration on wettability, mechanical properties, oil absorbency, and oil/water selectivity of the sponges were also investigated. The sponges exhibit fast magnetic responsivity and excellent superhydrophobicity/superoleophilicity (CAwater = 157° and CAoil ≈ 0°). The sponges also show very high efficiency in oil/water separation and could, driven by a magnet, quickly absorb floating oils on the water surface and heavy oils under water. Moreover, the PU@Fe3O4@SiO2@FP sponges could be used as membranes for oil/water separation and for continuous separation of large amounts of oil pollutants from the water surface with the help of a pump. The in turn binding of Fe3O4 nanoparticles, SiO2, and FP can also improve mechanical properties of the PU sponge. The sponges maintain the superhydrophobicity even when they are stretched with 200% strain or compressed with 50% strain. The sponges also show excellent mechanical stability, oil stability, and reusability in terms of superhydrophobicity and oil absorbency. The magnetic, durable, and superhydrophobic PU sponges are very promising materials for practical oil absorption and oil/water separation.