ABSTRACT
This study focuses on explaining the transport of solutes by nanofiltration of organic solvents.
Firstly, rejections are measured for 6 different solutes, dissolved in both methanol and ethanol, by 4 different membranes.
Secondly, the diffusive contribution to solute transport is determined. Therefore the diffusion coefficients of the solutes through the membranes are determined experimentally, using diffusion ceil measurements. It can be concluded that the diffusive contribution to the transport of the solutes through the membranes is very small (less than 5 %). The main transport mechanism therefore is convection, smce charge effects can be excluded.
Finally, several parameters are calculated, that are a measure for either the interaction between solute and membrane (diffusion coefficients, polarity), or the interaction between solute and solvent (Stokes radius) or the mteraction between solvent and membrane (contact angle). Taking these parameters into account, the observed rejections can be explained.
As a measure of de solute size in the presence of a certain solvent, the Stokes radius is used. The pore size of the membranes is influenced by solvation of the membrane material, which is dependent on the affinity between the solvent and the membrane and on the molecular size of the solvent molecule. The affinity between solvent en membranes can be quantified by the contact angle. For a larger Stokes radius and a more efficient solvation, the rejection of a solute will increase.
Finally, the rejection of a solute will depend on its size and polarity. The larger and more polar a component is, the lower the solute transport rate through the membrane and thus the higher the rejection will be.


Auteur: Hillen, An
Herkomst: 10230456 K.U.Leuven WMAG: (043)66/2004-13; 10239481 K.U.Leuven BIBC: THL80699
Referentie: Referentie