(464f) Liquid-Liquid Extraction of Volatile Fatty Acids (VFAs) Using Surfactants

Authors: 
Hernandez, R., University of Louisiana at Lafayette
Holmes, W., University of Louisiana at Lafayette
Zappi, M. E., University of Louisiana at Lafayette
Bajpai, R., University of Louisiana at Lafayette
Revellame, E., University of Louisiana at Lafayette

Liquid-Liquid Extraction of Volatile Fatty Acids (VFAs) using Surfactants

This research is focusing on the anaerobic digestion process, namely for VFA production. The acids of concern in this system, are acetic, propionic, and butyric acids. The main goal is to incorporate a liquid-liquid extraction stage during the digestion step to remove the produced VFAs from the resulting product. This will not only result in a VFA platform for specialty chemicals, but also prevent any product inhibition from the increase in acid concentration during the process. This requires ternary diagrams for each acid system separately, and then a final diagram for the three acid mixture system. Aspen Plus simulation is being used for theoretical modeling specifically using the UNIFAC and NRTL modeling tools. These two modeling tools are used for their interaction parameters based on the system that is being examined. As of now, the theoretical findings are promising with a rather large two phase envelope including mixtures of high water content, low acid content, and low surfactant content. Furthermore, the initial visual observations are almost identical to the theoretically modeled diagrams for the two phase envelope. The large two phase envelope will allow us to choose specific points that would fit in the process and even allow the desired in situ process. With an in situ process the system would be extracting the acids as they form, meaning that the composition of the system would be high in water and low in acids. While the initial visual observations will dictate the phase envelope line, phase compositional analysis is extremely important for tie line development making the diagram functional. Diagrams will be used to determine the surfactant amount needed to accomplish the desired extraction of the acids, based on the current system composition.