Mass transfer in membranes

Your objectives in studying this section are to be able to  

Define and apply the concepts permeability, permeance, permselectivity, separation factor, and cut. 

Understand the solution-diffusion model for separation of liquid and gas mixtures using dense, nonporous membranes. 

Explain the four idealized flow patterns in membrane modules. 

Apply the perfect-mixing and crossflow models to solve gas permeation problems in membrane modules. 

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Kubisova, L ., Sabolova, E., Schlosser, ., Martak, J. and Kertesz, R. (2004) Mass-transfer in membrane-based solvent extraction and stripping of 5-methyl-2-pyrazinecarboxylic acid and co-transport of sulphuric add in HF contactors. Desalination, 163, 27. 

Moulin PH, Veyret D, and Charbit F, Dean vortices Comparison of numerical simulation of shear stress and improvement of mass transfer in membrane processes at low permeation fluxes, J. Membr. Sci. 2001 183 148-162. 

Several research groups experimentally and theoretically reported the enhancement in mass transfer in membrane separation processes using Dean vortices, and their findings are summarized in Tables 1 and 2. 

The factor 0,808 arises from the oumerical compoution of a definite integral in the composition profile expression. The above ndutkm, which is valid only for short penetration distances where the velocity profile re me ms linear, predicts how the mass transfer rate is affected by the wall velocity gradient, Nnsselt07 provided a numerical solution of the above problem using the complete velocity profile expression, while Skelland" compares these results to experimental studies of mass transfer to laminar films. A number of similar problems am encountered when mass transfer in membrane systems is considered in Chapters 18-21. 

Evaluation of Kinetics and Mass Transfer in Membrane Reactors. 135... 

It is obvious that due to the diversity of membrane type and driving forces applied in each process, the mass transfer in membrane is governed by different mechanisms. For example, in a macroporous membrane the mass transfer does not rely on the chemical properties of the membrane, but on the contrary, in the case of tight membrane, the transfer and the separations are essentially due to the molecular interaction between the membrane and the solutes. 

T. G. Kauffnann and E. F. Leonard, Mechanism of Interfecial Mass Transfer in Membrane... 

Mass Transfer in Membrane Degasification Commercial membrane degasification units involve mass transfer in hollow-fiber modules where the vacuum and sweep gases are applied inside the fibers, and the water flows outside the flbers in cross flow perpendicular to the fiber axis. The mass transfer involves three sequential steps. First, dissolved gas diffuses out of the water to the membrane surface. Second, it diffuses into vapor pores in the walls of the hydrophobic hollow fibers. Third, when the dissolved gas reaches the other wall of the fibers, it diffuses into the surrounding nitrogen sweep gas in a high vacuum condition. 

W. Zhang, J. Li, G. Chen, W. You, Y. Jiang, W. Sun, Experimental study of mass transfer in membrane absorption process sing membranes with different porosities, Ind. Eng. Chem. Res. 49 (2010) 6641-6648. 

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