Background: Biomass pretreatment using certain ionic liquids (ILs) is very efficient, generally producing a substrate that is amenable to saccharification with fermentable sugar yields approaching theoretical limits. Although promising, several challenges must be addressed before an IL pretreatment technology can become commercially viable. One of the most significant challenges is the affordable and scalable recovery and recycle of the IL itself. Pervaporation (PV) is a highly selective and scalable membrane separation process for quantitatively recovering volatile solutes or solvents directly from non-volatile solvents that could prove more versatile for IL dehydration.

Results: We evaluated a commercially available PV system for IL dehydration and recycling as part of an integrated IL pretreatment process using 1-ethyl-3-methylimidazolium acetate ([C2C1Im][OAc]) that has been proven to be very effective as a biomass pretreatment solvent. Separation factors as high as 1500 were observed. We demonstrate that > 99.9 wt% [C2C1Im][OAc] can be recovered from aqueous solution (≤ 20 wt% IL) and recycled five times. A preliminary technoeconomic analysis validated the promising role of PV in improving overall biorefinery process economics, especially in the case where other IL recovery technologies might lead to significant losses.

Conclusions: These findings establish the foundation for further development of PV as an effective method of recovering and recycling ILs using a commercially viable process technology.

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Published in Biotechnology for Biofuels, v. 10, 154, p. 1-14.

© The Author(s) 2017

This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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This work conducted by the Joint BioEnergy Institute was supported by the Office of Science, Office of Biological and Environmental Research of the US Department of Energy under contract no. DE-AC02-05CH11231. The authors thank Chijioke (CJ) Joshua for the weight analysis of lignin after ultrafiltration and Dr. William F. Tivol for the assistance of SEM analysis. The effort at University of Kentucky is partially supported by the National Science Foundation under Cooperative Agreement No. 1355438. This research was undertaken, in part, thanks to funding from the Canada Excellence Research Chairs Program.

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The supporting data are given as electronic supporting information (ESI).

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Additional file 1: Figure S1-S8, Table S1.