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Membranes 2018, 8(4), 95; https://doi.org/10.3390/membranes8040095

Surface-Engineered Inorganic Nanoporous Membranes for Vapor and Pervaporative Separations of Water–Ethanol Mixtures

1
Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
2
National Renewable Energy Laboratory, Golden, CO 80401, USA
This manuscript has been authored by the UT-Battelle, LLC and Alliance for Sustainable Energy, LLC under Contracts No. DE-AC05-00OR22725 and No. DE-AC36-08-GO28308, respectively, with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).
*
Author to whom correspondence should be addressed.
Received: 27 July 2018 / Revised: 26 September 2018 / Accepted: 10 October 2018 / Published: 12 October 2018
(This article belongs to the Special Issue Nanostructured Membranes)
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Abstract

Surface wettability-tailored porous ceramic/metallic membranes (in the tubular and planar disc form) were prepared and studied for both vapor-phase separation and liquid pervaporative separations of water-ethanol mixtures. Superhydrophobic nanoceramic membranes demonstrated more selective permeation of ethanol (relative to water) by cross-flow pervaporation of liquid ethanol–water mixture (10 wt % ethanol feed at 80 °C). In addition, both superhydrophilic and superhydrophobic membranes were tested for the vapor-phase separations of water–ethanol mixtures. Porous inorganic membranes having relatively large nanopores (up to 8-nm) demonstrated good separation selectivity with higher permeation flux through a non-molecular-sieving mechanism. Due to surface-enhanced separation selectivity, larger nanopore-sized membranes (~5–100 nm) can be employed for both pervaporation and vapor phase separations to obtain higher selectivity (e.g., permselectivity for ethanol of 13.9 during pervaporation and a vapor phase separation factor of 1.6), with higher flux due to larger nanopores than the traditional size-exclusion membranes (e.g., inorganic zeolite-based membranes having sub-nanometer pores). The prepared superhydrophobic porous inorganic membranes in this work showed good thermal stability (i.e., the large contact angle remains the same after 300 °C for 4 h) and chemical stability to ethanol, while the silica-textured superhydrophilic surfaced membranes can tolerate even higher temperatures. These surface-engineered metallic/ceramic nanoporous membranes should have better high-temperature tolerance for hot vapor processing than those reported for polymeric membranes. View Full-Text
Keywords: inorganic membranes; nanoporous membranes; superhydrophobic; superhydrophilic; ethanol separations; dewatering; dehydration inorganic membranes; nanoporous membranes; superhydrophobic; superhydrophilic; ethanol separations; dewatering; dehydration
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Hu, M.Z.; Engtrakul, C.; Bischoff, B.L.; Lu, M.; Alemseghed, M. Surface-Engineered Inorganic Nanoporous Membranes for Vapor and Pervaporative Separations of Water–Ethanol Mixtures. Membranes 2018, 8, 95.

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