Projet ANR-07-BLAN-0188 – PROMEMSEL : Physico-chimie et transfert de solutés organiques à travers des membranes en présence de sel
Programme : Blanc (BLANC) 2007
Année de financement : 2007
Coordinateur du projet : UNIVERSITE TOULOUSE III [PAUL SABATIER] (UNIVERSITE TOULOUSE III [PAUL SABATIER])
Partenaires : Centre national de la recherche scientifique; Université de Franche-Comté; Université de Toulouse III - Paul Sabatier
Montant : 450000.0 euros
Date de début : 2007
Durée : 48 mois
Résumé : "The application field of membrane processes is growing to fluids of increasing complexity, containing both mineral and organic compounds sometimes at high concentrations. This is specially the case in the food industry for organic acids, dairy products, sugars,..., as well as for environmental applications for the treatment of brines, lixiviates, concentrates... -  So, different studies, concerned with the integration of membrane operations, were carried out these last years in partnership with companies to investigate technological solutions for process intensification. -  For instance, the integration of nanofiltration in the processes used for the production of organic acids was studied with EURODIA industry. In collaboration with Veolia Environnement, the improvement of the biological treatment of industrial wastes containing organic pollutants and mineral salts was investigated. It was pointed out that the performances can be seriously damaged when solutions containing significant amount of salt are involved. The influence of the presence of salts on the transfer of neutral organic solutes, like polysaccharides and organic acids, was emphasized. With porous nanofiltration membranes as well as with ion-exchange ones, used in electrodialysis, the mass transfer of an organic solute increases with the salt concentration and this increase depends on the salt nature. Then, as far as a purification is to be achieved, the selectivity can be very poor with respect to the one expected. For instance, in common NF conditions, the retention of glucose, which is about 80% for a pure solution, can be reduced to 20% in presence of salt. The originality of these studies, some of them being carried out by the partners of the project, lies in the identification of the transversal character of these effects which seem to be common for different species, membranes and driving forces. -  Different phenomena were proposed to explain such results, like the swelling of the membrane material, the change of the apparent size of the neutral solute due to a ""salting-out"" effect,... Thus, whilst it is now demonstrated that the ionic content has a great importance with respect to the membrane processes performances, the mechanisms involved are still not fully identified and at least not quantified. -  In this context, the aim of the project is to go further through the understanding of the mechanisms governing the mass transfer of organic solutes through membrane separators and specially their dependence on the ionic composition. The objective is also to provide a better prediction of the performances of these membrane processes applied to different situations, involving such kind of liquids containing both organic compounds and salts, where the selectivity is a target. -  In this project, specialists of physico-chemistry of solutions and materials, and processes (mass transfer mechanisms) will work together to face the multidisciplinary character of the study. -  Two kinds of membrane operations will be specially investigated: Nanofiltration, which is a pressure driven process using nanoporous membranes, and Electrodialysis, an electrically driven process, using ion exchange membranes. -  A methodology will be developed to determine relevant physicochemical parameters to characterise the solutes, in solutions of different ion compositions, and the membranes and to assess the relationship between these parameters and those characterising the mass transfer through confined media, like membranes. -  On one hand, dedicated experimental methods capable of providing the relevant physicochemical parameters with respect to the characterisation of both solutions and materials will be investigated. For solutions for instance, volumetric properties will be considered since they are expected to provide useful informations concerning the hydration state of neutral organic solute. -  On the other hand, experimental and theoretical approaches will be used in para