The performance of superhydrophobic and superoleophilic carbon nanotube meshes in water–oil filtration

• Published in: Carbon (New York) 2011-02, Vol.49 (2), p.669-676
• Main Authors: Lee, Chee Huei, Johnson, Nick, Drelich, Jaroslaw, Yap, Yoke Khin
• Format: Article
• Language: English
• Subjects: air; alkanes; aluminum oxide; Blockage; Carbon; carbon nanotubes; Chemical vapor deposition; Chemistry; Colloidal state and disperse state; Contact angle; Cross-disciplinary physics: materials science; rheology; Droplets; Emulsions; Exact sciences and technology; films (materials); filtrates; Filtration; Fullerenes and related materials; diamonds, graphite; gasoline; General and physical chemistry; hydrophobicity; Materials science; Membranes; oils; particle size; Physics; porosity; Porous materials; Quantitative analysis; Solid-liquid interface; Specific materials; stainless steel; Surface physical chemistry; vapors; water
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2010.10.016

CNTs grown on stainless steel mesh can dewater water–oil emulsion with 80% efficiency by blocking water droplets larger than the mesh opening due to superhydrophobicity of CNTs. Oil can penetrate through the mesh due to oleophilicity of CNTs. Some small water droplets can also leak through the mesh. [Display omitted] ► Carbon nanotubes grown on stainless steel mesh forms three-dimensional porous structures (SS-CNT meshes). ► The superhydrophobic SS-CNT meshes can dewater water–oil emulsion with 80% efficiency by blocking large water droplet. ► The superoleophilic SS-CNT meshes allow oil to leak through. Vertically-aligned multi-walled carbon nanotubes (CNTs) were grown on stainless steel (SS) mesh by thermal chemical vapor deposition with a diffusion barrier of Al 2O 3 film. These three-dimensional porous structures (SS-CNT meshes) were found to be superhydrophobic and superoleophilic. Water advancing contact angles of 145–150° were determined for these SS-CNT meshes in air and oil (gasoline, isooctane). Oil, on the other hand, completely wet the SS-CNT meshes. This combined superhydrophobic and superoleophilic property repelled water while allowed the permeation of oil. Filtration tests demonstrated efficiencies better than 80% of these SS-CNT meshes as the filtration membranes of the water-in-oil emulsions. We have conducted quantitative analysis on the diameters of the oil droplets in both the feed emulsion and the filtrate. Then, we have evaluated the issue of water blockage and possible way to improve the filtration efficiency. Finally, the filtration and blockage mechanisms are proposed.