Le présent travail porte sur l’étude comparative des procédés d’électrodialyse et d’électrodéionisation. Les possibilités d’application des procédés électro-membranaires à la production d’acide lactique par voie fermentaire sont investiguées. Deux axes de recherche sont choisis : le premier consiste à extraire de manière continue le lactate de sodium hors du milieu de fermentation. Pour cela, un empilement d’électrodialyse ne comportant que des membranes anioniques est couplé au fermenteur : environ 95 % des ions lactate sont extraits lors de l’opération. Par comparaison avec une fermentation témoin en mode batch, aucune inhibition de la fermentation n’est observée, et la productivité est multipliée par 13. Le deuxième axe de recherche consiste à convertir le lactate de sodium en acide lactique : un taux de purification comparable à celui obtenu en échange d’ions est recherché. Un procédé continu d’électrodéionisation à membranes bipolaires permettant d’atteindre 99,9 % de taux de conversion est élaboré pour le traitement de produit dilué. Est présentée finalement la modélisation mathématique d’un compartiment d’électodéionisation : les points expérimentaux sont fortement similaires aux points recalculés / This work deals with the comparative study of electrodialysis and electrodeionization. The possibilities to integrate the electro-membrane processes in the lactic acid fermentive production lines are investigated. Two main research ways are chosen : the first one lies in the continuous extraction of natrium lactate out of the fermentation middle. For this, an electrodialysis stack of only anionic membranes is coupled with the fermenter : approximately 95 % of lactate are removed during the operation. By comparison with a standard fermentation in batch mode, no inhibition is observed, and the productivity is increased by 13. The second way is to convert the natrium lactate in lactic acid : a high purity rate is seeked. A continuous electrodeioniation process including bipolar membranes, leading to 99,9% conversion rate, is elaborated for the treatment of diluted solutions. Finally is presented the mathematic calculation of an electrodeionization compartment : experimental points and calculated values are very similar

Increased levels of nitrate in ground water have made many wells unsuitable as sources for drinking water. In this thesis an ion-exchang eassisted electromembrane process, suitable for nitrate removal, is investigated both theoretically and experimentally. An ion-exchange textile material is introduced as a conducting spacer in the feed compartment of an electropermutation cell. The sheet shaped structure of the textile makes it easy to incorporate into the cell. High permeability and fast ion-exchange kinetics, compared to ion-exchange resins, are other attractive features of the ion-exchange textile. A steady-state model based on the conservation of the ionic species is developed. The governing equations on the microscopic level are volume averaged to give macro-homogeneous equations. The model equations are analyzed and relevant simplifications are motivated and introduced. Dimensionless parameters governing the continuous electropermutation process are identified and their influence on the process are discussed. The mathematical model can be used as a tool when optimising the process parameters and designing equipment. An experimental study that aimed to show the positive influence of using the ion-exchange textile in the feed compartment of an continuous electropermutation process is presented. The incorporation of the ion-exchange textile significantly improves the nitrate removal rate at the same time as the power consumption is decreased. A superficial solution of sodium nitrate with a initial nitrate concentration of 105 ppm was treated. A product stream with less than 20 ppm nitrate could be obtained, in a single pass mode of operation. Its concluded from these experiments that continuous electropermutation using ion-exchange textile provides an interesting alternative for nitrate removal, in drinking water production. The predictions of the mathematical model are compared with experimental results and a good agreement is obtained. Enhanced water dissociation is known to take place at the surface of ion-exchange membranes in electromembrane processes operated above the limiting current density. A model for this enhanced water dissociation in presented in the thesis. The model makes it possible to incorporate the effect of water dissociation as a heterogeneous surface reaction. Results from simulations of electropermutation with and without ion-exchange textile incorporated are presented. The influence of the water dissociation is investigated with the developed model. / QC 20101118

<p>Increased levels of nitrate in ground water have made many wells unsuitable as sources for drinking water. In this thesis an ion-exchang eassisted electromembrane process, suitable for nitrate removal, is investigated both theoretically and experimentally. An ion-exchange textile material is introduced as a conducting spacer in the feed compartment of an electropermutation cell. The sheet shaped structure of the textile makes it easy to incorporate into the cell. High permeability and fast ion-exchange kinetics, compared to ion-exchange resins, are other attractive features of the ion-exchange textile.</p><p>A steady-state model based on the conservation of the ionic species is developed. The governing equations on the microscopic level are volume averaged to give macro-homogeneous equations. The model equations are analyzed and relevant simplifications are motivated and introduced. Dimensionless parameters governing the continuous electropermutation process are identified and their influence on the process are discussed. The mathematical model can be used as a tool when optimising the process parameters and designing equipment.</p><p>An experimental study that aimed to show the positive influence of using the ion-exchange textile in the feed compartment of an continuous electropermutation process is presented. The incorporation of the ion-exchange textile significantly improves the nitrate removal rate at the same time as the power consumption is decreased. A superficial solution of sodium nitrate with a initial nitrate concentration of 105 ppm was treated. A product stream with less than 20 ppm nitrate could be obtained, in a single pass mode of operation. Its concluded from these experiments that continuous electropermutation using ion-exchange textile provides an interesting alternative for nitrate removal, in drinking water production. The predictions of the mathematical model are compared with experimental results and a good agreement is obtained.</p><p>Enhanced water dissociation is known to take place at the surface of ion-exchange membranes in electromembrane processes operated above the limiting current density. A model for this enhanced water dissociation in presented in the thesis. The model makes it possible to incorporate the effect of water dissociation as a heterogeneous surface reaction. Results from simulations of electropermutation with and without ion-exchange textile incorporated are presented. The influence of the water dissociation is investigated with the developed model.</p>