Impact des champs électriques pulsés à courte durée d'impulsion/pause sur le colmatage des membranes en cours de procédés électromembranaires: mécanismes d'action et influence sur les performances des procédés

L’approvisionnement en eau potable fraîche, en aliments sains, en substances bioactives et en énergie peut être accompli par une technologie verte comme l’électrodialyse (ED). Actuellement, deux obstacles majeurs entravent l’utilisation d’une telle technologie par l’industrie, soit les phénomènes de colmatage membranaire et la polarisation de la concentration (CP). Les travaux récents ont démontré que l’application d’un champ électrique pulsé (CEP) pendant l’ED peut éliminer complètement le colmatage par les protéines et peut diminuer considérablement le colmatage par les minéraux. De plus, les impulsions de courant préviennent l’élargissement de la couche de CP. Malgré des résultats prometteurs d’application du CEP, la durée optimale des impulsions/pauses et l’influence du CEP sur le colmatage membranaire et la CP dans des solutions contenant les agents d’encrassement sont encore des questions ouvertes et discutables. Les résultats de la thèse montrent que les champs électriques pulsés avec des durées d’impulsion/pause courtes peuvent être appliqués pour éliminer complètement le colmatage minéral sur les membranes échangeuses d’anions et pour contrôler le colmatage minéral sur le membranes échangeuses de cations au cours des procédés électromembranaires. De plus, l’application de courants surlimites provoquant la formation de vortex électroconvectifs a des avantages en matière de diminution du colmatage et d’amélioration de la performance des procédés. Il est démontré pour la première fois dans cette thèse qu’il est possible d’appliquer un champ électrique pulsé sur des cellule d’électrodialyse comprenant dans leur configuration membranaire une ou plusieurs membrane(s) bipolaire(s). Finalement, des traitements électromembranaires efficaces de solutions contenant des protéines peuvent être effectués par couplage avec des membranes d’ultrafiltration: ce couplage permet d’éviter la formation de colmatage protéique au sein de la cellule d’ED.Supply of fresh drinking water, healthy food, bio-active substances and power may be accomplished by ecofriendly electrodialysis (ED) technology. Nowadays, two main barriers such as membrane fouling and concentration polarization (CP) phenomena stand in the way of ED processes. Recent works demonstrated that application of pulsed electric field (PEF) during ED might completely eliminate protein fouling and drastically decrease fouling by minerals (scaling). Moreover, the current pulsations prevent widening of concentration polarization layer. In spite of the promising results of PEF application, the optimal duration of pulse/pause lapses and influence of PEF on membrane fouling and CP in the solutions containing fouling agents are still opened and disputable questions. The thesis results demonstrate that PEF with short pulse/pause durations can be applied to electromembrane processes in order to avoid completely the scaling on anion-exchange membrane and to control the scaling on cation-exchange membrane. Moreover, “overlimiting” currents inducing the formation of electroconvective vortices are advantageous from the point of scaling decrease and improvement of process performance. The possible application of PEF to ED systems with bipolar membrane(s) was demonstrated for the first time. Furthermore, effective electromembrane treatments of solutions containing proteins could be performed with pretreatment by ultrafiltration membrane, which avoids the clogging of ED stack

Milk protein production by a more environmentally sustainable process : bipolar membrane electrodialysis coupled with ultrafiltration

The increased demand for food production to nourish the rapidly growing human population raises serious sustainability issues for the food sector. Indeed, conventional food production lines involve processes having a significant environmental burden. Hence, the present study aims to demonstrate an environmentally sustainable process of food production. The milk protein was chosen as a model food ingredient due to its exceptional role in the human diet. The proposed innovative process of milk protein production includes bipolar membrane electrodialysis coupled with ultrafiltration (EDBM-UF). The crucial problem during the EDBM-UF of milk, such as different types of membrane fouling, was successfully solved. Moreover, the life cycle assessment of the novel EDBM-UF protein production process was carried out and compared to a conventional acid/base process. Additionally, a sensitivity test of electricity supply at different geographical locations of the world was performed since electricity is the main energy source for the EDBM-UF process and it could be derived from different sources (renewable and non-renewable). The assessment results demonstrate that the proposed electromembrane process has significant environmental benefits compared to the conventional process using chemicals independently from the electricity supply mix from all considered geographical locations. Thus, EDBM-UF could become a prospective industrial technology taking into account environmental concerns and promoting the development of healthy human society

How Overlimiting Current Condition Influences Lactic Acid Recovery and Demineralization by Electrodialysis with Nanofiltration Membrane: Comparison with Conventional Electrodialysis

Acid whey is the main co-product resulting from the production of fresh cheeses and Greek-type yogurts. It generally goes through a spray-drying process prior to valorization, but it needs to be deacidified (lactic acid recovery) and demineralized beforehand to obtain a powder of quality with all the preserved compounds of interest such as lactose and proteins. Electrodialysis (ED) is a process actually used for acid whey treatment, but scaling formation at the surface of the ion-exchange membrane is still a major problem. In this work, a combination of two new avenues of ED treatment has been studied. First, the integration of a nanofiltration (NF) membrane in an ED conventional stack was compared to a classical ED stack with an anion-exchange membrane in a standard current condition. Secondly, both configurations were tested in the overlimiting current condition to study the impact of electroconvective vortices on process efficiency. The combined effects of the NF membrane and overlimiting current condition led to a higher lactic acid recovery rate of acid whey (40%), while the conventional ED stack in the overlimiting current condition led to a higher demineralization (87% based on the total cation concentration). Those effects were related to the conductivity, pH, global resistance, and energy consumption of each treatment that are influenced by water splitting phenomenon, which was decreased in the overlimiting condition

Impact of Electric Arcs and Pulsed Electric Fields on the Functional Properties of Beta-Lactoglobulin

Beta-lactoglobulin (β-lg) is a major whey protein with various techno-functional properties that can be improved by several treatments. Therefore, the objective of this study was to explore the impact of green high-voltage electrical treatments (HVETs)—namely, pulsed electric fields and electric arcs—on the functional properties of β-lg. Both emulsifying and foaming stability and capacity, as well as the hygroscopicity of non-treated and pretreated β-lg, were explored. The results demonstrated that the emulsifying capacity and stability of pretreated samples increased by 43% and 22% when compared to native β-lg, respectively. Likewise, the pretreated β-lg displayed better foaming stability compared to native β-lg. In addition, the HVETs significantly decreased the hygroscopicity of β-lg (by 48% on average), making it a good ingredient with reduced hygroscopicity for the food industry

The influence of information about nutritional quality, environmental impact and eco-efficiency of menu items on consumer perceptions and behaviors

While food and dietary patterns are major determinants of a population’s health, our daily food choices also put pressure on the environment. In that context, providing graphical and comprehensive information is a widely used and potentially promising communication tool to promote healthier and more environmentally sustainable choices when eating out-of-home. Hence, the purpose of this study was to assess the influence of information about environmental impact and nutritional quality of meal options on consumers’ food choices, consumption and perceptions. A total of 80 men and 80 women were recruited, consisting of students and employees of Université Laval (Quebec City, Canada). Participants were randomly assigned to one of four experimental conditions, with menu information displaying: 1) greenhouse gas emissions scores, 2) nutritional quality scores, 3) eco-efficiency scores or 4) no information (control). Participants had to choose between two meals (i.e., beef burritos or chicken meal) both showing one of the above-mentioned conditions and then consume the chosen meal. Results indicated that nutritional and environmental information had an impact on meal choice. More specifically, participants exposed to such information tended to choose more frequently the meal with the most favorable score for the related condition (p-values 0.05). These findings suggest that communicating information about environmental impact and nutritional quality of menu items to consumers within institutional settings could be relevant to tackle more sustainable food choices

Electrochemical Acidification of Kraft Black Liquor: Effect of Fouling and Chemical Cleaning on Ion Exchange Membrane Integrity

In the essence of the green biorefinery concept an interest in further implementations of wood compounds has gained a lot of attention. Therefore, it is crucial to identify and develop efficient and eco-friendly extraction processes. In particular in a lignin biorefinery plant, electrochemical acidification of Kraft black liquor via electrodialysis with bipolar membrane is considered as a sustainable avenue to acidify the Kraft black liquor and subsequently extract lignin. Even though the application of this acidification technique results in less chemical consumption than the acid precipitation method, the colloidal fouling of the ion exchange (bipolar and cation exchange) membranes, adversely affects its performance. This study was performed to determine the influence of the colloidal fouling and chemical cleaning process on the integrity of the membranes. Four commercially available cation exchange membranes and one bipolar membrane were examined. Membrane analyses, such as thickness, contact angle, ion exchange capacity and electrical resistance measurements, as well as scanning electron microscopy with energy dispersive X-ray analysis, were carried out. It was found that changing the type of the cation-exchange membrane cannot eliminate the fouling phenomenon and a chemical cleaning cycle is required. Caustic soda and fresh diluted black liquor were tested as the cleaning solutions. The initial properties of the bipolar membrane and two cation-exchange membranes (CMB and Nafion 324) were reestablished after the chemical cleaning step. Furthermore, in terms of sustainability concept, the utilization of in situ and free of charge fresh diluted black liquor, as the cleaning agent, can be an interesting eco-efficient approach