Oxygen mass transfer to emulsions in bubble column contactor
Integration of life sciences & engineering
Integration of Life Sciences & Engineering - Poster (T5-P)
Keywords: oxygen mass transfer, biphasic systems, oil-in-water emulsions, surfactants
Nowadays, the understanding of gas mass transfer by absorption processes when a heterogeneous system is employed as absorbent medium is an important tool with growing interest. Gas-liquid-liquid systems are encountered in many reactions, such as in homogeneous biphasic catalysis, and in numerous biotechnological processes based on the development of microorganisms within a biphasic medium [1]. Oil-in-water emulsions are found in aerobic culture media where an inert hydrophobic compound is used with the purpose of improving oxygen transfer rate from the gas to the medium, but also in bioprocesses where the oil phase is the substrate of the biological reaction.
A small number of studies about this field have been carried out, and conclusions obtained about the mass transfer mechanism are contradictory in relation to the influence of the oil phase in the absorbent medium into the contactor [2].
Present work includes an exhaustive study about the absorption process by the analysis of volumetric mass transfer coefficient and the corresponding value of interfacial area between gas phase and liquid heterogeneous medium generated in the bubble contactor. This procedure allows to calculate the value of the individual mass transfer coefficient. These results increase the knowledge about mass transfer mechanism in these complex biphasic systems.
A system composed by water, castor oil and Tween 80 has been used as a model, since it is the base of the medium used for an aroma production from the biotransformation of ricinoleic acid using a yeast [3]. The contactor set-up was a rectangular bubble column. This geometry was chosen in order to obtain a better definition of gas bubbles photographs, for interfacial area determination process.
The influence of the presence of surfactant and organic phase upon the interfacial area and on the mass transfer coefficient have been analysed with the aim of improving the determination of the gas mass transfer mechanism in emulsions. The experimental data allows to conclude that the presence of surfactant plays an important role upon global mass transfer, modifying both parameters: mass transfer coefficient and interfacial area.
References
1. Pulido-Mayoral, N.; Galindo, E. Phases dispersion and oxygen transfer in a simulated fermentation broth containing castor oil and proteins. Biotechnol. Prog. 20 (2004) 1608-1613.
2. Dumont, E.; Delmas, H. Mass transfer enhancement of gas absorption in oil-in-water systems: a review. Chem. Eng. Process. 42 (2003) 419-438.
3. Aguedo, M.; Gomes, N.; Garcia, E.E.; Waché, Y.; Mota , M.; Teixeira, J.A.; Belo I. Decalactones production by Yarrowia lipolytica under increased O2 transfer rates. Biotechnol. Lett. 27 (2005) 1617-1621.
Presented Wednesday 19, 13:30 to 15:00, in session Integration of Life Sciences & Engineering - Poster (T5-P).
