Extraction and purification of volatile fatty acids

• Main Author: Struyf, Alexis
• Other Authors: UCL - Faculté des bioingénieurs, Castel, Guillaume, Gerin, Patrick A.
• Format: Master Thesis
• Language: English
• Published: 2018
• Subjects: Volatile fatty acids; Recovery; Ion exchange resin; Carbon dioxide; Carbonic acid
• Online Access: http://hdl.handle.net/2078.1/thesis:14913

This master thesis was realized in the Earth and Life Institute (ELI) in the cluster of Applied Microbiology. The aim of this research was to contribute to the development of a new process for the extraction and purification of volatile fatty acids, short-chain carboxylic acids that are produced during acidogenic fermentation. Volatile fatty acids find numerous uses in green chemistry, food and pharmaceutical industry. VFAs are conventionally produced by petrochemical pathways not sustainable nor environmental-friendly. Therefore, increasing attention has been given in the recovery of VFAs from microbial origin. We investigated the potential of adsorption and desorption on ion exchange resins and non-ionic resin for the extraction and purification of VFAs from fermentation liquor. Our experiments were performed with model acetic and butyric acids aqueous solutions. One focus was to investigate CO2-mediated desorption of VFAs, since CO2 is cheap and available at production sites, and can be converted into carbonic acid, an interesting candidate for VFA desorption. The VFAs from initially acidic solutions were more adsorbed than from more alkaline solutions, on all resins tested. Considering the initial amount of VFA in the model solution, fractions of more than 0.9 VFAs were adsorbed on the ion exchange resins in acidic conditions. Adsorption on the non-ionic resin was more selective for butyric acid. Adsorption equilibrium was reached within the first 15 minutes for the macroporous strong base ion exchange resin and nonionic resin, while it was reached within 60 minutes for the gel weak base exchange resin. CO2-mediated desorption was tested by using a reactor containing the resins suspended in water under a CO2-pressure. Under 40 bars of CO2 inside de the reactor and using a strong anion exchanger with a capacity equivalent to the VFA introduced, a molar fraction of 0.44 moles of acetic acid was desorbed by CO2, per mole of acetic acid initially introduced. The VFAs desorption is proportional to the square root ...