Professor, European Institute of Membranes (IEM), Montpellier, France
Prof. Denis Bouyer is a full Professor in European Institute of Membranes (IEM), Montpellier, France. He is team leader of Chemical Engineering department and has fourteen years’ experience in polymeric membrane preparation. His membrane research activities involve the modeling of the polymeric membrane formation, such as mass and heat transfer and/or chemical reactions. Recently, he investigated the membrane formation dynamics using the phase field method (based on Cahn-Hilliard equation). From 2003, he has supervised 16 PhD and during the last decade he was been involved in 7 industrial collaborations and in 10 ANR projects (2 international) on Membrane Technologies and he was coordinator of 3 ANR projects. He has also published more than 50 international peer-reviewed articles, three patents with international extension and 3 book chapters. He is guest editor for a special issue “modeling the membrane formation” for the international journal “Membranes (ISSN 2077-0375)”.
The modeling of membrane formation is a very tricky but exciting challenge, which could help preventing the classical trial-and-error process classically used by industrials to adjust the operating parameters. In a recent past, numerical models have been developed for simulating the mass transfer phenomena prior to phase inversion. They involved Flory Huggins theory (thermodynamics) and free volumes theory (diffusion of small molecules in the polymer matrix).
In IEM, we recently developed a new type of membranes in agreement with principles of green chemistry, i.e. with water soluble polymers (HPC, PVA) and without the use of organic solvent. For such case, the phase separation was induced by an original LCST-TIPS process, i.e. the polymer solution was heated above the Lower Critical Solution Temperature (LCST). The crosslinking of the polymer was carried out by chemical cross-linking using the Glutaraldehyde (GA) to prevent resolubilization in aqueous solution during further filtration. Hence, concomitant phenomena were thus involved in the membrane formation mechanisms: (i) phase separation, (ii) chemical cross-linking and (iii) solvent evaporation.
The modelling approach was developed to calculate the evaporation rate during the phase separation and the model involved: (i) the Flory-Huggins theory for simulating the thermodynamics of the polymer system, (ii) mass transfer within the polymer matrix based on free-volume theory and RMN experiments for self-diffusion coefficients, (iii) dedicated diffusion formalisms for diluted systems, and (iv) semi-empirical correlations for the external mass transfer. A system of partial differential equations was solved to simulate and predict the composition path during the phase separation process, from the polymer solution to the dry porous membrane.
Thanks to the numerical model, the most appropriate operating conditions were therefore determined to obtain a porous membrane with appropriate morphology for friltration.