Aeration and Extraction in Multiphase Biological Reactors
authors Mara Guadalupe Freire Martins Martins
supervisors João Manuel da Costa Araújo Pereira Coutinho; Isabel Marrucho
thesis type PhD
abstract The aim of this work is the understanding and optimization of aeration and extraction phenomena in multiphase biological reactors. The aeration may be enhanced in aerobic bioreactors by the use of a second liquid immiscible phase such as fluorocompounds. Perfluorocarbons have peculiar properties, where among others, present a large solubility for oxygen and are bio and chemically inert. The addition of a second liquid phase in aqueous bioreactors can be performed both by the direct inclusion of the perfluorocarbons or in the form of emulsions using a surfactant. The choice of the best fluorocarbon depends on their oxygen solubility capability, on their mass transfer coefficients and on their emulsion stability, being all these properties influenced in a second order, by the physical properties of the pure compounds. This work contributes with new experimental data for several pure fluorocarbon properties such as surface tensions and viscosities. Furthermore, new methods were developed for the inspection of the solubility of oxygen in perfluorocarbonformulated emulsions and for studying the perfluorocarbon-in-water emulsions stability along time. Also, the mutual solubilities between fluorocarbons and water were carried and the effect of the salts addition was studied. Finally, the mass transfer coefficient to the aqueous phase using a perfluorocarbon as a second liquid phase and the bioreactor structural optimization were achieved. Ionic liquids are a novel class of chemical compounds that present a large range of interesting properties, where their large solvating ability, their negligible vapour pressures and the possibility of fine tune their physical properties, make of them ideal candidates for “green solvents”. Therefore, their ability as extraction solvents from biological reactors aqueous phases was carried. Original data for mutual solubilities with water were measured for a large combination of ionic liquids. Besides, new data for pure physical properties such as densities and surface tensions were determined and the influence of the water content on such properties was discussed. COSMO-RS, a predictive method based on unimolecular quantum chemical calculations for individual molecules, was used to predict the phase behaviour between fluorocarbons or ionic liquids and water and the predictive capacity of this model is discussed.
year published 2007
subject category Chemical Engineering