Mineral Acid Co-Extraction in Reactive Extraction of Lactic Acid Using a Thymol-Menthol Deep Eutectic Solvent as a Green Modifier

Paul Demmelmayer, Marija Ćosić, Marlene Kienberger*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Carboxylic acids can be isolated from fermentation broths using reactive liquid-liquid extraction, offering an alternative to the environmentally harmful state-of-the-art process of precipitating calcium lactate. To enhance the sustainability of liquid-liquid extraction processes, greener solvents, such as natural deep eutectic solvents, are investigated. However, fermentation broths often exhibit pH values unsuitable for carboxylic acid extraction, which can be adjusted using mineral acids, though mineral acids may be co-extracted. In this study, we systematically examine the co-extraction of hydrochloric, nitric, sulfuric, and phosphoric acid during extraction and back-extraction of lactic acid. The solvent phase consisted of tri-n-octylamine, trioctylphosphine oxide, or tributyl phosphate diluted in a thymol-menthol deep eutectic solvent. The back-extraction was conducted using a diluent swing with p-cymene as the antisolvent and water as the receiving phase. Tri-n-octylamine showed the highest efficiency for lactic acid (up to 29.8%) but also the highest co-extraction of mineral acids (up to 50.9%). In contrast, trioctylphosphine oxide exhibited a lower but more selective lactic acid extraction (5.94%) with low mineral acids co-extraction (0.135%). Overall, the highest co-extraction was observed for phosphoric acid and the lowest for nitric acid. In conclusion, the selected solvent phase composition and mineral acid influence the co-extraction and, thus, final product purity. The successful application of the natural deep eutectic solvent as the modifier enhances the sustainability of liquid–liquid extraction processes.
Original languageEnglish
Article number1722
JournalMolecules
Volume29
Issue number8
DOIs
Publication statusPublished - 11 Apr 2024

Keywords

  • lactic acid extraction
  • mineral acid extraction
  • natural deep eutectic solvent
  • reactive extraction

ASJC Scopus subject areas

  • Drug Discovery
  • Analytical Chemistry
  • Chemistry (miscellaneous)
  • Molecular Medicine
  • Physical and Theoretical Chemistry
  • Pharmaceutical Science
  • Organic Chemistry

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