Temperature dependence modeling of reverse osmosis
Gábor Lakner, J.F. Lakner, Gábor Rácz, M. Kłos
Abstract
ABSTRACT Osmosis is the natural flow of a solvent through a semi-permeable membrane from a less concentrated solution to a more concentrated one. This is driven by the osmotic pressure difference. If opposing external pressure exceeding the osmotic pressure is used, the solvent will flow from the more concentrated solution toward the less concentrated one. This is reverse osmosis, whose main characteristic, as for any mass transfer process, is the mass transfer coefficient. This mass transfer coefficient is dependent on temperature, and there are several empirical correlations for it. In this study, an Arrhenius-type correlation is deduced for the temperature dependence of the mass transfer coefficient based on the Poiseuille law, which appropriately describes the dependence of both the solvent (water) flow through the membrane and the salt rejection – as the most important characteristic of the system – on the handling temperature. The activation energy, E a = 25 kJ mol –1 , determined on the basis of the Arrhenius correlation, is equal to that of the transmembrane processes and can be linked to the membrane structure. The controlling of the model was certified by reverse osmotic desalination of seawater based on independent measurements from the literature.