2021 : Butyric acid separation from aqueous solution using MIBK extraction solvent with the aid of biological buffer as a green auxiliary agent

Dr Afan Hamzah S.T



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Bio renewable feedstocks are particularly promising as alternative to the fossil resources which would minimize the negative impact on the environment and reduce the dependence on fossil resources for the production of fuels and chemicals. Carboxylic acid is useful material which can be produced by fermentation from biomass as bio renewable resources. Carboxylic acid has significant applications in the fuel, pharmaceutical, chemicals or solvents, and food industries. Butyric acid is one of carboxylic acids that has many benefits in industries. Currently, it is widely used as a mixture in biofuels. Thus, it is important to study the separation of carboxylic acid (butyric acid) from its aqueous solution to obtain high purity of product. Liquid-liquid extraction is a beneficial process in carboxylic acid production to recover carboxylic acid from aqueous solution (fermentation broth). Liquid-liquid equilibrium data are needed for rational design and optimal separation operation, like biological separation and extraction processes. The objective of this study is to determine liquid-liquid equilibrium (LLE) data for quaternary systems of butyric acid, water, MIBK (Methyl Isobutyl Ketone), biological buffer at 303.15 K and atmospheric pressure. The effect of biological buffer addition into aqueous solution are also studied. Three different biological buffers, EPPS (4-(2-hydroxyethyl)-1-piperazine propanesulfonic acid), HEPES (4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid), and MOPS (4-morpholinepropanesulfonic acid) are applied in this study for the comparison. Buffering-out may be used to recover butyric acid from its aqueous solution via new process which may not cause corrosion and require less energy. Two liquid phases are formed after adding MIBK extraction solvent and the separation may be enhanced by the addition of certain amount of biological buffer as a green auxiliary agent in the aqueous solution. Based on our best knowledge, there are still no LLE data for carboxylic acid-water-organic solvent-biological buffer systems. Hence, we introduce new systems for the recovery of carboxylic acid (butyric acid) from aqueous solution in this study. The separation factor and distribution coefficient are evaluated in this study to interpret the extraction performance of butyric acid. Othmer-Tobias correlation is used to ascertain the reliability of the experimental tie-line data. Then, the NRTL (Non-Random Two-Liquid) model is applied to correlate the experimental LLE data. The binary interaction parameters of NRTL model obtained in this study can be applied to perform LLE calculation in extraction column design. Furthermore, this study can also open a scope for the thermodynamics studies of carboxylic acid biphasic extraction systems.