Ultra porous nanocellulose aerogels as separation medium for mixtures of oil/water liquids
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Ultra porous nanocellulose aerogels as separation medium for mixtures of oil/water liquids Nicholas Tchang Cervin • Christian Aulin Per Tomas Larsson • Lars Wa˚gberg
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Received: 15 August 2011 / Accepted: 23 November 2011 / Published online: 17 December 2011 Ó Springer Science+Business Media B.V. 2011
Abstract A novel type of sponge-like material for the separation of mixed oil and water liquids has been prepared by the vapour deposition of hydrophobic silanes on ultra-porous nanocellulose aerogels. To achieve this, a highly porous ([99%) nanocellulose aerogel with high structural flexibility and robustness is first formed by freeze-drying an aqueous dispersion of the nanocellulose. The density, pore size distribution and wetting properties of the aerogel can be tuned by selecting the concentration of the nanocellulose dispersion before freeze-drying. The hydrophobic light- weight aerogels are almost instantly filled with the oil phase when selectively absorbing oil from water, with a capacity to absorb up to 45 times their own weight in oil. The oil can also be drained from the
Electronic supplementary material The online version of this article (doi:10.1007/s10570-011-9629-5) contains supplementary material, which is available to authorized users. N. T. Cervin (&) C. Aulin P. T. Larsson L. Wa˚gberg Wallenberg Wood Science Center, KTH Royal Institute of Technology, Teknikringen 56, 10044 Stockholm, Sweden e-mail: [email protected] C. Aulin P. T. Larsson L. Wa˚gberg Innventia AB, Box 5604, 11486 Stockholm, Sweden P. T. Larsson L. Wa˚gberg Department of Fibre and Polymer Technology, School of Chemical Science and Engineering, KTH Royal Institute of Technology, Teknikringen 56, 10044 Stockholm, Sweden
aerogel and the aerogel can then be reused for a second absorption cycle. Keywords Absorption Aerogel Cellulose Desorption Oleophilic Separation Superhydrophobic
Introduction Aerogels are ultra-light, highly porous materials typically manufactured by subjecting a wet-gel precursor to critical-point-drying (CPD) or lyophilization (freeze-drying) in order to remove liquid without collapsing the network. Microscopically, aerogels are composed of tenuous networks of clustered nanoparticles, and the materials often have unique properties, including very high strength-to-density and surfacearea-to-volume ratios. To date most aerogels are fabricated from silica (Hrubesh 1998) or pyrolized organic polymers (Pekala 1989; Pekala et al. 1998). A typical problem has been their fragility which has limited their use in applications where robustness is needed. To overcome this problem, aerogels based on native cellulose nanofibril networks were recently introduced, which are less brittle and more flexible in facile and relevant ways (Paakko et al. 2008). The long and entangled native cellulose nanofibrils form an aerogel network with a fibrillar morphology and strong molecular interactions including both van der Waals
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interactions and hydrogen bonds, and they are therefore suitable for various templ
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