Environmentally benign and durable superhydrophobic coatings based on short fluorocarbon chain siloxane modified halloysite nanotubes for oil/water separation

Fluorinated siloxane (F-Si(OCH3)(3)) was synthesized from perfluoro (2-methyl-3-oxyhexyl) fluorine and N-(beta-aminoethyl)-gamma-aminopropyltrimethoxy silane, and then was used for hydrophobic modification of halloysite nanotubes (F-HNTs). A mixture of epoxy resin and F-HNTs was sprayed onto the surface of the stainless steel mesh. F-HNTs enhanced the surface roughness and reduced the surface energy, giving the mesh super-hydrophobic/superlipophilic properties. The static water contact angle of coated mesh can reach 155.4 +/- 0.3 degrees. A series of oil and water mixtures can be separated, and the separation efficiency was higher than 97.8 +/- 0.3%. After 50 cycles, the separation efficiency was still higher than 96.2 +/- 0.5%. The coating mesh also had high separation efficiency for oil-water mixtures with different volume ratios and pH values. More importantly, the coated mesh still showed good stability in the harsh test conditions, such as strong acid, strong alkali, sand-paper wear and so on. Since the preparation of the coated mesh has the advantages of simplicity, scalability, and economy, it is expected to be applied on a large scale in the field of oil-water separation in the future.