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Sci Adv. 2019 Aug 2;5(8):eaaw3203. doi: 10.1126/sciadv.aaw3203. eCollection 2019 Aug.

Hydrophobic nanostructured wood membrane for thermally efficient distillation.

Author information

1
Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, Boulder, CO 80303, USA.
2
Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA.
3
Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544, USA.
4
Department of Mechanical Engineering, University of Colorado Boulder, Boulder, CO 80309, USA.
5
Department of Civil and Environmental Engineering, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
6
State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
7
Department of Civil and Environmental Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA.

Abstract

Current membrane distillation (MD) is challenged by the inefficiency of water thermal separation from dissolved solutes, controlled by membrane porosity and thermal conductivity. Existing petroleum-derived polymeric membranes face major development barriers. Here, we demonstrate a first robust MD membrane directly fabricated from sustainable wood material. The hydrophobic nanowood membrane had high porosity (89 ± 3%) and hierarchical pore structure with a wide pore size distribution of crystalline cellulose nanofibrils and xylem vessels and lumina (channels) that facilitate water vapor transportation. The thermal conductivity was extremely low in the transverse direction, which reduces conductive heat transport. However, high thermal conductivity along the fiber enables efficient thermal dissipation along the axial direction. As a result, the membrane demonstrated excellent intrinsic vapor permeability (1.44 ± 0.09 kg m-1 K-1 s-1 Pa-1) and thermal efficiency (~70% at 60°C). The properties of thermal efficiency, water flux, scalability, and sustainability make nanowood highly desirable for MD applications.

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