**5. Conclusions**

In this study, the solid–liquid equilibria of a binary 1,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH][OAc])–water compound system as well as layer and suspension freeze crystallization as a concentration method were investigated. The main conclusions that can be drawn from this study are as follows:


**Supplementary Materials:** The following are available online at http://www.mdpi.com/2073-4352/10/3/147/s1, Figure S1: Schematic diagram of extracting thermal data from a DSC curve, Table S1: Liquidus and glass transition (or eutectic temperature) temperatures extracted from DSC curves, Table S2: Layer freeze crystallization data of aqueous 3 wt.% [DBNH][OAc] solutions with a freezing time of 40 min, Table S3: Layer freeze crystallization data of aqueous 3 wt.% [DBNH][OAc] solutions with a freezing time of 60 min, Table S4: Layer freeze crystallization data of aqueous 6 wt.% [DBNH][OAc] solutions with a freezing time of 40 min, Table S5: Layer freeze crystallization data of aqueous 6 wt.% [DBNH][OAc] solutions with a freezing time of 60 min, Table S6: Suspension freeze crystallization data of aqueous 3 wt.% [DBNH][OAc] solutions with a freezing time of 40 min, Table S7: Suspension freeze crystallization data of aqueous 3 wt.% [DBNH][OAc] solutions with a freezing time of 60 min, Table S8: Suspension freeze crystallization data of aqueous 6 wt.% [DBNH][OAc] solutions with a freezing time of 40 min, Table S9: Suspension freeze crystallization data of aqueous 6 wt.% [DBNH][OAc] solutions with a freezing time of 60 min.

**Author Contributions:** Conceptualization of freeze crystallization experiments, N.O. and M.L.-K.; conceptualization of DSC analysis, L.Y. and H.L.; methodology, validation, and investigation of freeze crystallization, N.O.; methodology, validation, and investigation of DSC analysis L.Y.; writing—original draft, N.O.; writing—review and editing, N.O., L.Y., and M.L.-K.; visualization, N.O. and L.Y.; supervision, M.L.-K. and H.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** The first author is thankful to Aalto CHEM's funding for financial support.

**Acknowledgments:** The authors are grateful to Han Bing and Peter Schulze for their valuable assistance during experimental work as well as to Sanna Hellsten for providing synthetized ionic liquid.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
