A phenomenological model to evaluate the performances of electrodialysis for the desalination of saline water containing organic solutes

Abstract

Electrodialysis is promising to treat saline solutions containing organic solutes. However, there is still a need for a model to describe the desalination performances according to the process parameters. In this work a phenomenological model is proposed based on the analysis of the different contributions to the mass transfer of salt, water, and organic compounds. Once the characteristic parameters are determined experimentally, it is possible to predict the salt and organic concentrations in both compartments according to the operating conditions. The methodology is illustrated for the evaluation of electrodialysis performances considering a case study, and the effect of the current and solution compositions are discussed. To remove a fixed salt quantity, a lower current gives a higher organic solute transfer due to a higher time dependent solute diffusion, the additional transfer, fixed by the quantity of charge, remaining constant. Regarding the influence of the inorganic salts, higher transfer of organics, like glucose, acetic acid or acetate, are observed with sulfate compared to chloride, while a contrary behavior is obtained with phenol. This model also permits to discuss the influence of possible pretreatments to change the pH or the salt composition in order to improve the electrodialysis performances.