TY - JOUR
T1 - Thymol-menthol-based deep eutectic solvent as a modifier in reactive liquid–liquid extraction of carboxylic acids from pretreated sweet sorghum silage press juice
AU - Demmelmayer, Paul
AU - Steiner, Lena
AU - Weber, Hansjörg
AU - Kienberger, Marlene
PY - 2023/4/1
Y1 - 2023/4/1
N2 - Reactive liquid–liquid extraction has been widely investigated as a means of isolating carboxylic acids from fermentation broths. However, commonly applied fossil-based solvent phases should be replaced by green alternatives. In this work, we investigate a thymol-menthol-based deep eutectic solvent (tmDES) as a green alternative to the commonly applied modifier 1–octanol for the extraction of lactic acid, acetic acid, and oxalic acid from a model solution and pre-treated sweet sorghum silage press juice (pSPJ); tri–n–octylamine (TOA) was used as a reactive extractant. Additionally, NMR spectroscopy was used to detect interactions between menthol and thymol molecules, as well as among these and TOA and lactic acid. NMR measurements of tmDES revealed the existence of multiple intermolecular contacts between thymol and menthol. Furthermore, nuclear Overhauser effects (NOEs) between the tmDES, TOA, and lactic acid molecules were found. Extraction experiments showed that tmDES improves the extraction efficiency when using pSPJ as the feed phase. The maximum extraction efficiency for lactic acid increased from 35.0 ± 0.8 % to 48.7 ± 0.7 % and for acetic acid from 52.4 ± 0.2 % to 82.2 ± 0.6 % when using a tmDES instead of 1–octanol at 50 °C. Furthermore, the use of tmDES resulted in higher extraction efficiencies as compared to the use of 1–octanol at equilibrium pH values ranging from five to seven, which is a common pH range for fermentation. Besides having superior biocompatibility and extraction efficiency as compared to 1–octanol, tmDES allow carboxylic acid extraction processes to be carried out at higher pH levels.
AB - Reactive liquid–liquid extraction has been widely investigated as a means of isolating carboxylic acids from fermentation broths. However, commonly applied fossil-based solvent phases should be replaced by green alternatives. In this work, we investigate a thymol-menthol-based deep eutectic solvent (tmDES) as a green alternative to the commonly applied modifier 1–octanol for the extraction of lactic acid, acetic acid, and oxalic acid from a model solution and pre-treated sweet sorghum silage press juice (pSPJ); tri–n–octylamine (TOA) was used as a reactive extractant. Additionally, NMR spectroscopy was used to detect interactions between menthol and thymol molecules, as well as among these and TOA and lactic acid. NMR measurements of tmDES revealed the existence of multiple intermolecular contacts between thymol and menthol. Furthermore, nuclear Overhauser effects (NOEs) between the tmDES, TOA, and lactic acid molecules were found. Extraction experiments showed that tmDES improves the extraction efficiency when using pSPJ as the feed phase. The maximum extraction efficiency for lactic acid increased from 35.0 ± 0.8 % to 48.7 ± 0.7 % and for acetic acid from 52.4 ± 0.2 % to 82.2 ± 0.6 % when using a tmDES instead of 1–octanol at 50 °C. Furthermore, the use of tmDES resulted in higher extraction efficiencies as compared to the use of 1–octanol at equilibrium pH values ranging from five to seven, which is a common pH range for fermentation. Besides having superior biocompatibility and extraction efficiency as compared to 1–octanol, tmDES allow carboxylic acid extraction processes to be carried out at higher pH levels.
KW - Biorefinery
KW - Deep eutectic solvents
KW - Lactic acid
KW - NMR spectroscopy
KW - Reactive extraction
KW - Silage
UR - http://www.scopus.com/inward/record.url?scp=85146481861&partnerID=8YFLogxK
U2 - 10.1016/j.seppur.2022.123060
DO - 10.1016/j.seppur.2022.123060
M3 - Article
SN - 1383-5866
VL - 310
JO - Separation and Purification Technology
JF - Separation and Purification Technology
M1 - 123060
ER -