Electrodialysis With Bipolar Membranes Research Articles

Optimizing operational parameters for highly-concentrated sodium hydroxide production via electrodialysis with bipolar membranes from concentrated brines

Sodium hydroxide necessitates the implementation of cleaner production methods that deviate from the conventional practices in the chlor-alkali industry. New sustainable sources such as concentrated brines, which are typically regarded as waste, are currently being investigated for the production of sodium hydroxide using Electrodialysis with Bipolar Membranes (EDBM). This process has the advantages of not producing gas by-products, reducing operational risks, and providing value to waste brines after converting them into acids or alkali solutions. However, the production of sodium hydroxide via EDBM using brines is limited by the low concentration of the final base (e.g. typically below 2 M), which increases the cost of transport. This study aims to overcome this limitation by optimizing parameters such as salt-to-base volume ratio, initial salt concentration, and current density values. Notably, this research is one of the few to employ Response Surface Methodology with a Central Composite Design to maximize the final sodium hydroxide concentration; two models using second-order polynomial equations were proposed. Results showed the possibility to achieve 5.3 M NaOH under a volume ratio range of 9.8:1–10:1, a current density range of 490 A/m−2 to 500 A/m−2, and an initial salt concentration in the range of 6 M NaCl. Moreover, the energetic analysis showed values of specific energy consumption in a range of 2.5 kWh kgNaOH-1-3.5 kWh kgNaOH-1 and specific productivity of the process up to 3.08 tonNaOH year−1 m−2, which are moderate in comparison with values previously presented in literature. Finally, an economic analysis showed that energy was the most significant cost component, making up 89 % of the total process cost, which was estimated to be 0.69 € kgNaOH-1 (concentration 21.2 % w/w). Overall, these high concentration values open a real chance to shift towards sustainable production of NaOH by means of EDBM from brines, highlighting the novelty of this study.

Techno-economic feasibility of photovoltaic solar electrodialysis with bipolar membranes

Electrodialysis with bipolar membranes (EDBM) can transform concentrated brines into acids and bases through the application of an electric field. Nevertheless, the widespread use of EDBM is limited by its high energy consumption, typically based on fossil fuels. Yet, the integration of EDBM with renewable energy sources, like solar photovoltaic (PV), remains unexplored. This study presents a techno-economic analysis of PV-EDBM to produce NaOH and HCl from seawater reverse osmosis (SWRO) brines. An integrated PV-EDBM model was developed and applied to a hypothetical PV-EDBM plant located in the SWRO facility of Lampedusa (Italy). Results revealed that PV has no negative impact on the performance in terms of product concentration, specific energy consumption and current efficiency. Meanwhile, the levelized cost of NaOH for PV-EDBM was reduced by 20 % in comparison to the electrical grid mix, achieving 210 €·ton−1 NaOH on an annual average for PV-EDBM. Therefore, the investment associated with PV is offset by the benefits of reduced electricity costs from the grid. Consequently, EDBM emerges as a feasible solution to address resource scarcity, representing a significant step towards integrating renewable energies with advanced wastewater treatment technologies, thus paving the path to a greener future.

Production of biohydrogen and green platform compound 2, 5-furandicarboxylic acid using rice straw hydrolysate

Lignocellulosic hydrolysate contains several inhibitors that hinder downstream biological processes. The immobilized strain Burkholderia sp. H-2 was used in this study to biodetoxify real rice straw hydrolysate and biotransform 5-hydroxymethylfurfural (5-HMF), an inhibitor, into 2, 5-furandicarboxylic acid (FDCA), a valuable platform compound. An electrodialysis with bipolar membranes (EDBM) system was applied to recover FDCA and perform secondary detoxification of the biodetoxified real rice straw hydrolysate. The rice straw hydrolysate after biodetoxification and EDBM treatment was used for anaerobic dark fermentative hydrogen production. The immobilized Burkholderia sp. H-2 could completely biotransform 1843 mg/L 5-HMF into 1532 mg/L FDCA within 24 h when the 2-fold diluted rice straw hydrolysate was used as the feedstock. The optimal EDBM system parameters to recover FDCA were a hydrolysate pH of 6, operated at a current density of 17.86 mA/cm2. The FDCA recovery efficiency was 44.6 %, when using the biodetoxified real rice straw hydrolysate as the EDBM feedstock. The rice straw hydrolysate after biodetoxification and EDBM treatment had better biohydrogen production performance than the undetoxified and biodetoxified rice straw hydrolysates.

In-depth insights on multi-ionic transport in Electrodialysis with bipolar membrane systems

Electrodialysis with Bipolar Membranes (EDBM) has become a key technology for valorising waste brine streams as a new chemical production route. Even though its application has been widely studied using single electrolyte solutions (e.g., NaCl or Na2SO4), there is still a lack of knowledge about using multi-ionic mixtures. For the first time, this work aims to evaluate the EDBM performance when treating synthetic solutions mimicking the waste brines produced in a integrated process for the valorisation of solar saltworks bitterns. The behaviour of a lab-scale EDBM unit was assessed using SUEZ ion exchange membranes (IEMs), operating at 300 A m−2, and the ion transport through IEMs was investigated, based on the calculation of apparent transport numbers and selectivities.The results highlighted that multi-ionic solutions barely affected the production of hydroxide ions. Chlorides were transported up to 7 times faster than sulphates across the anion-exchange membranes, while the cation-exchange membranes exhibited slightly higher selectivity for potassium than for sodium (∼1.2). The current efficiencies ranged between 70 % and 80 %, while a minimum specific energy consumption of 1.60 kWh kg-1NaOH was obtained for the most concentrated brine at 1 mol L-1 OH–.These results provide novel and valuable information to support the development and implementation of EDBM as a sustainable technology for supporting a resource-efficient and competitive economy through on-site and delocalized chemicals production routes.

Electrodialysis with Bipolar Membranes for the Sustainable Production of Chemicals from Seawater Brines at Pilot Plant Scale.

Environmental concerns regarding the disposal of seawater reverse osmosis brines require the development of new valorization strategies. Electrodialysis with bipolar membrane (EDBM) technology enables the production of acid and base from a salty waste stream. In this study, an EDBM pilot plant with a membrane area of 19.2 m2 was tested. This total membrane area results much larger (i.e., more than 16 times larger) than those reported in the literature so far for the production of HCl and NaOH aqueous solutions, starting from NaCl brines. The pilot unit was tested both in continuous and discontinuous operation modes, at different current densities (200-500 A m-2). Particularly, three different process configurations were evaluated, namely, closed-loop, feed and bleed, and fed-batch. At lower applied current density (200 A m-2), the closed-loop had a lower specific energy consumption (SEC) (1.4 kWh kg-1) and a higher current efficiency (CE) (80%). When the current density was increased (300-500 A m-2), the feed and bleed mode was more appropriate due to its low values of SEC (1.9-2.6 kWh kg-1) as well as high values of specific production (SP) (0.82-1.3 ton year-1 m-2) and current efficiency (63-67%). These results showed the effect of various process configurations on the performance of the EDBM, thereby guiding the selection of the most suitable process configuration when varying the operating conditions and representing a first important step toward the implementation of this technology at industrial scale.

Analysis of Operational Parameters in Acid and Base Production Using an Electrodialysis with Bipolar Membranes Pilot Plant

In agreement with the Water Framework Directive, Circular Economy and European Union (EU) Green Deal packages, the EU-funded WATER-MINING project aims to validate next-generation water resource solutions at the pre-commercial demonstration scale in order to provide water management and recovery of valuable materials from alternative sources. In the framework of the WATER-MINING project, desalination brines from the Lampedusa (Italy) seawater reverse osmosis (SWRO) plant will be used to produce freshwater and recover valuable salts by integrating different technologies. In particular, electrodialysis with bipolar membranes (EDBM) will be used to produce chemicals (NaOH and HCl). A novel EDBM pilot plant (6.4 m2, FuMa-Tech) has been installed and operated. The performance of EDBM for single pass under different flowrates (2-8 L·min-1) for acid, base and saline channels, and two current densities (200 and 400 A·m-2), has been analyzed in terms of specific energy consumption (SEC) and current efficiency (CE). Results showed that by increasing the flowrates, generation of HCl and NaOH slightly increased. For example, ΔOH- shifted from 0.76 to 0.79 mol·min-1 when the flowrate increased from 2 to 7.5 L·min-1 at 200 A·m-2. Moreover, SEC decreased (1.18-1.05 kWh·kg-1) while CE increased (87.0-93.4%), achieving minimum (1.02 kWh·kg-1) and maximum (99.4%) values, respectively, at 6 L·min-1.

Electrodialysis with Bipolar Membranes for the Generation of NaOH and HCl Solutions from Brines: An Inter-Laboratory Evaluation of Thin and Ultrathin Non-Woven Cloth-Based Ion-Exchange Membranes.

The SEArcularMINE project aims to recover critical raw materials (CRMs) from brines from saltworks, thus facing a CRM shortage within Europe. To promote a fully circular scheme, the project valorises concentrated brines using electrodialysis with bipolar membranes (EDBM) to generate the required amounts of reactants (i.e., acids and bases). Regarding the performances of new non-woven cloth ion-exchange membranes (Suez): (i) an ultra-thin non-woven polyester cloth and (ii) a thin polypropylene cloth acting as the support structures were assessed. Additionally, the anion layer includes a catalyst to promote the water dissociation reaction. The effect of current density (100, 200, and 300 A m-2) on the performance of two combinations of membranes in an inter-laboratory exercise using 2 M NaCl was evaluated. According to statistical analysis ANOVA, there was an agreement on the results obtained in both laboratories. NaOH/HCl solutions up to 0.8 M were generated working at 300 A m-2 using both combinations of membranes. Regarding the performance parameters, stack set-ups incorporating thin polypropylene membranes showed lower specific energy consumption (SEC) and higher specific productivity (SP) than ultra-thin polypropylene ones. Hence, for ultra-thin polypropylene membranes, SEC was reported to be between 2.18 and 1.69 kWh kg-1NaOH and SP between 974 and 314 kg m-2 y-1.

Circular production – Evaluation of membrane technologies for nutrient recycling from a microbial fermentation effluent

The present study demonstrates a detailed analysis of nutrient recovery from the spent fermentation broth of S. acidocaldarius, an archaeon with high industrial and pharmaceutical potential. The pathways of the resource recovery by the lately recognized environmental-friendly and cost-effective technologies nanofiltration (NF), electrodialysis (ED), and electrodialysis with bipolar membranes (EDBM) were assessed. In contrast to previous research, this study treated real wastewater and tested the reuse of recovered products in the subsequent batch fermentations. Ions were separated from the rest of the medium by NF, with 78–85% DOC removal and 0.74 kWh/m3. ED achieved a 1.7 concentration factor for ions, 96% DOC removal and 0.51–0.74 kWh/kg of removed salts. EDBM coupled with NF removed 94.8–98.1% DOC while recovering 0.11–0.15 M sulfuric acid from the feed containing 6.1–16.7 g/l of SO42− with energy consumption of 2.7–3 kWh/kgH2SO4. Recovered media were successfully applied for control fermentations. While NF was less energy-consuming, ED/EDBM offered a selective ion recovery, higher concentration factors and reuse-specific streams. The discharges of NF/ED/EDBM showed reduced negative environmental impacts due to the nutrient removal from the waste fermentation effluent. All applied technologies require a post-treatment to remove organic substances from side streams and close the production loop with a near-to-zero liquid and waste discharge.

Technical and Environmental Feasibilities of the Commercial Production of NaOH from Brine by Means of an Integrated EDBM and Evaporation Process.

Electrodialysis with bipolar membranes (EDBMs) is a technology that offers a great potential for the introduction of the principles of a circular economy in the desalination industry, by providing a strategy for the recovery of HCl and NaOH from brine via the process of seawater reverse osmosis (SWRO). Both chemicals are widely employed in desalination facilities, however NaOH presents a special interest due to its higher requirements and cost. Nevertheless, the standard commercial concentrations that are commonly employed in the facilities cannot be obtained using the state of the art EDBM technology itself. Therefore, the aim and main purpose of this work is to prove the technical and environmental feasibilities of a new approach to produce commercial NaOH (50%wt.) from SWRO brine by means of an integrated process of EDBMs followed by a triple effect evaporation. The global process has been technically evaluated in terms of the specific energy consumption (SEC) (kWh·kg−1 NaOH) and the environmental sustainability performance has been analyzed by its carbon footprint (CF) (kg CO2-eq.·kg−1 NaOH). The influence of the current density, and the power source in the EDBM stage have been evaluated on a laboratory scale while the influence of the feed stream concentration in the evaporation stage has been obtained through simulations using Aspen Plus. The lowest SEC of the integrated process (SECOV), 31.1 kWh·kg−1 NaOH, is obtained when an average current density of 500 A·m−2, provided by a power supply (grid mix), is applied in the EDBM stage. The environmental burdens of the integrated process have been quantified by achieving reductions in the CF by up to 54.7% when solar photovoltaic energy is employed as the power source for EDBMs, with a value of 5.38 kg CO2-eq.·kg−1 NaOH. This study presents a great potential for the introduction of the principles of a circular economy in the water industry through the recovery of NaOH from the high salinity waste stream generated in SWRO facilities and opens the possibility of the reuse of NaOH by its self-supply in the desalination plant.

Describing ion transport and water splitting in an electrodialysis stack with bipolar membranes by a 2-D model: Experimental validation

Electrodialysis with bipolar membranes (EDBM) has drawn attention motivated by their application in generating reagents from salts. Due to the water splitting (WS) occurring at the junction of the bipolar membranes (BPMs), where the anion and cation layers are in strict contact, H+ and OH- are released from the BPM producing acid and alkali on the respective compartment. Considering this application, the interest of this work is to provide further understanding of the mechanisms of WS and transport of species in EDBM. This work develops and utilizes, for the first time, an experimentally validated two-dimensional (2-D) computational model, in which the Navier-Stokes and Nernst-Planck equations are coupled with the description of WS given by the Second Wien effect. In addition, a 1-D geometry is also proposed to perform a comparison between electroneutrality and Poisson charge conservation. The model is computationally solved using COMSOL Multiphysics. According to simulations, electroneutrality is valid for 2-D geometries. Moreover, the semipermeable characteristics of the membranes are assessed by means of evidencing a polarization effect resulting in a double-electric layer. The model proposed predicts a significant proton leakage, and facilitates the study of WS within the BPMs.

Towards sustainable production of minerals and chemicals through seawater brine treatment using Eutectic freeze crystallization and Electrodialysis with bipolar membranes

European policy encourages the adoption of sustainable systems that promote the efficient use and recovery of minerals and chemicals. In this respect, desalination brines do contain a dramatic amount of valuable minerals and can be valorized through appropriate treatments rather than releasing them into the environment. This paper proposes an innovative brine recovery system for obtaining high purity chemicals through the integration of Eutectic Freeze Crystallization (EFC) and Electrodialysis with Bipolar Membrane (EDBM) technologies. Two separate laboratory-scale experimental campaigns were carried out to validate the potential integration of the two processes. Mirabilite (Na2SO4∙10H2O) has been recovered with a purity of 99.9% using the EFC, and a feed rich in NaCl with low impurities has been further processed in an EDBM unit. EDBM tests with feed solutions simulating EFC effluents have shown that it is possible to produce acidic and basic solutions with high purity (>99%), despite the presence of impurities in the feed. Interestingly, the low EDBM specific consumptions of 0.9–1.1 kWh kg−1NaOH at 100 A m−2 and 1.3–1.6 kWh kg−1NaOH at 300 A m−2 were comparable with and without impurities. In the context of the circular economy strategy promoted by the EU-H2020 Water Mining project, the current study demonstrates that this integrated system effectively minimizes waste, promoting sustainability while providing a potential economic return.

Phospholipid recovery from sweet whey by combination of electrodialytic processes and understanding of specific mechanisms involved

Electrodialysis with bipolar membrane (EDBM) combined with a subsequent 4–6 fold dilution was demonstrated to allow high phospholipid (PL) recovery and defatting rate. However, the economic and environmental drawbacks of such dilution limit the process application in the food industry. To overcome them, original combinations of treatment with EDBM, applicable in the food industry (demineralization by conventional electrodialysis (ED) and diafiltration), were tested for the first time and compared with the EDBM + dilution process. The most promising combination was the EDBM + ED process. Indeed, demineralization by ED after EDBM allowed to reach the highest divalent cation removal (70.2 % versus 2.3 and 39.7 % respectively for dilution and diafiltration) and defatting rate (76.6 % versus 54.2 and 23.0 % respectively for dilution and diafiltration). Furthermore, this combination allowed to concentrate phosphatidylethanolamine by 15 X compared to its content in initial sweet whey and to reach the highest PL yield (25.9 g/100 L of sweet whey versus 13.3 and 8.99 g/100 L respectively for dilution and diafiltration). These high performances were associated with different phenomena occurring during the treatments performed after EDBM and leading to specific impacts on ionic strength, mineral content and composition. From those phenomena, it was possible to understand the key role of the removal of divalent cations in the formation of lipoprotein complexes, highlighting that it was not only due to the reduction in pH and ionic strength. Consequently, EDBM combined with ED appears to be an attractive industrial process, as it combined the ecofriendly advantages of electrodialytic technics, while limiting water consumption, avoiding the production of large volumes of effluents and the use of chemical agents.

Production of Demineralized Antibacterial, Antifungal and Antioxidant Peptides from Bovine Hemoglobin Using an Optimized Multiple-Step System: Electrodialysis with Bipolar Membrane.

Numerous studies have shown that bovine hemoglobin, a protein from slaughterhouse waste, has important biological potential after conventional enzymatic hydrolysis. However, the active peptides could not be considered pure since they contained mineral salts. Therefore, an optimized multi-step process of electrodialysis with bipolar membranes (EDBM) was carried out to produce discolored and demineralized peptides without the addition of chemical agents. The aim of this study was to test the antibacterial, antifungal and antioxidant activities of discolored and demineralized bovine hemoglobin hydrolysates recovered by EDBM and to compare them with raw and discolored hydrolysates derived from conventional hydrolysis. The results demonstrate that discolored–demineralized hydrolysates recovered from EDBM had significant antimicrobial activity against many bacterial (gram-positive and gram-negative) and fungal (molds and yeast) strains. Concerning antibacterial activity, lower MIC values for hydrolysates were registered against Staphylococcus aureus, Kocuria rhizophila and Listeria monocytogenes. For antifungal activity, lower MIC values for hydrolysates were registered against Paecilomyces spp., Rhodotorula mucilaginosa and Mucor racemosus. Hemoglobin hydrolysates showed fungicidal mechanisms towards these fungal strains since the MFC/MIC ratio was ≤4. The hydrolysates also showed a potent antioxidant effect in four different antioxidant tests. Consequently, they can be considered promising natural, low-salt food preservatives. To the best of our knowledge, no previous studies have identified the biological properties of discolored and demineralized bovine hemoglobin hydrolysates.

Mathematical Modeling of the Effect of Pulsed Electric Field Mode and Solution Flow Rate on Protein Fouling during Bipolar Membrane Electroacidificaiton of Caseinate Solution.

A one-dimensional non-stationary model was developed for a better understanding of the protein fouling formation mechanism during electroacidification of caseinate solution using electrodialysis with bipolar membranes (EDBM) in pulsed electric field (PEF) mode. Four different PEF modes were investigated with pulse–pause durations of 10–10 s, 10–20 s, 10–33 s, 10–50 s. For each current mode 3 different flow rates were considered, corresponding to Reynolds numbers, Re, equal to 187, 374 and 560. The processes are considered in the diffusion boundary layer between the surface of the cation-exchange layer of bipolar membrane and bulk solution of the desalination compartment. The Nernst–Planck and material balance equation systems describe the ion transport. The electroneutrality condition and equilibrium chemical reactions are taken into account. The calculation results using the developed model are in qualitative agreement with the experimental data obtained during the previous experimental part of the study. It is confirmed that both the electrical PEF mode and the flow rate have a significant effect on the thickness (and mass) of the protein fouling during EDBM. Moreover, the choice of the electric current mode has the main impact on the fouling formation rate; an increase in the PEF pause duration leads to a decrease in the amount of fouling. It was shown that an increase in the PEF pause duration from 10 s to 50 s, in combination with an increase in Reynolds number (the flow rate) from 187 to 560, makes it possible to reduce synergistically the mass of protein deposits from 6 to 1.3 mg/cm2, which corresponds to a 78% decrease.

Purification of organic acids using electrodialysis with bipolar membranes (EDBM) combined with monovalent anion selective membranes

• EDBM used to purify a mixture of lactate and citrate as a simulated beet molasses solution. • The use of a monovalent selective anion exchange membrane gives higher purity than with a standard AEM. • Adjustment of the feed to pH > 9.0 improves separation due to the larger size of the citrate anion. • A volume ratio of 10:1 acid:feed gives 153 g/L lactic acid of 95% purity with <2.7 KWh per kg lactate. • The BP-A-C configuration is more energy efficient than BP-A. The feasibility of using electrodialysis with bipolar membranes (EDBM), combined with monovalent selective anion exchange membranes was investigated to purify organic acids from fermentation broths or wastewater streams. A simulated beet molasses feed containing a mixture of monobasic lactic acid and polybasic citric acid was used for this purpose. The impact of the feed pH, the configuration of the membrane stack and the voltage applied on the selectivity of the process was investigated. At a pH of 9–10 and an electric field intensity of 9 V/cm, a lactic acid product with a purity of at least 97% can be obtained by using both two chamber (BP-A) and three chamber (BP-A-C) configurations with the monovalent selective membrane. When using the BP-A configuration, the hydroxide ions generated by the bipolar membrane compete with the lactate anions to move into the acid solution and so the energy efficiency is lower than with the BP-A-C configuration. To mimic a multiple pass process and increase the lactic acid concentration of the final product, experiments were performed across a range of volume ratios between the feed and acid solutions. As this ratio is varied, the purity of lactic acid produced remains higher than 95% while the energy consumption is essentially unaffected. Due to the osmotic flow of water during experiments, the highest lactic acid concentration that can be achieved is limited to 153 g/L at a volume ratio (V A : V F ) of 1:10.

The Concentration of Organic Acids in Cranberry Juice Modulates the Gut Microbiota in Mice.

A daily consumption of cranberry juice (CJ) is linked to many beneficial health effects due to its richness in polyphenols but could also awake some intestinal discomforts due to its organic acid content and possibly lead to intestinal inflammation. Additionally, the impact of such a juice on the gut microbiota is still unknown. Thus, this study aimed to determine the impacts of a daily consumption of CJ and its successive deacidification on the intestinal inflammation and on the gut microbiota in mice. Four deacidified CJs (DCJs) (deacidification rates of 0, 40, 60, and 80%) were produced by electrodialysis with bipolar membrane (EDBM) and administered to C57BL/6J mice for four weeks, while the diet (CHOW) and the water were ad libitum. Different parameters were measured to determine intestinal inflammation when the gut microbiota was profiled. Treatment with a 0% DCJ did not induce intestinal inflammation but increased the gut microbiota diversity and induced a modulation of its functions in comparison with control (water). The effect of the removal of the organic acid content of CJ on the decrease of intestinal inflammation could not be observed. However, deacidification by EDBM of CJ induced an additional increase, in comparison with a 0% DCJ, in the Lachnospiraceae family which have beneficial effects and functions associated with protection of the intestine: the lower the organic acid content, the more bacteria of the Lachnospiraceae family and functions having a positive impact on the gut microbiota.

Fouling Mitigation by Optimizing Flow Rate and Pulsed Electric Field during Bipolar Membrane Electroacidification of Caseinate Solution

The efficiency of separation processes using ion exchange membranes (IEMs), especially in the food industry, is significantly limited by the fouling phenomenon, which is the process of the attachment and growth of certain species on the surface and inside the membrane. Pulsed electric field (PEF) mode, which consists in the application of constant current density pulses during a fixed time (Ton) alternated with pause lapses (Toff), has a positive antifouling impact. The aim of this study was to investigate the combined effect of three different relatively high flow rates of feed solution (corresponding to Reynolds numbers of 187, 374 and 560) and various pulse–pause ratios of PEF current regime on protein fouling kinetics during electrodialysis with bipolar membranes (EDBM) of a model caseinate solution. Four different pulse/pause regimes (with Ton/Toff ratios equal to 10 s/10 s, 10 s/20 s, 10 s/33 s and 10 s/50 s) during electrodialysis (ED) treatment were evaluated at a current density of 5 mA/cm2. It was found that increasing the pause duration and caseinate solution flow rate had a positive impact on the minimization of protein fouling occurring on the cationic surface of the bipolar membrane (BPM) during the EDBM. Both a long pause and high flow rate contribute to a more effective decrease in the concentration of protons and caseinate anions at the BPM surface: a very good membrane performance was achieved with 50 s of pause duration of PEF and a flow rate corresponding to Re = 374. A further increase in PEF pause duration (above 50 s) or flow rate (above Re = 374) did not lead to a significant decrease in the amount of fouling.

Phospholipid recovery from sweet whey and whey protein concentrate: Use of electrodialysis with bipolar membrane combined with a dilution factor as an ecoefficient method

Electrodialysis with bipolar membrane (EDBM) is promising to recover phospholipids (PLs) from sweet whey and whey protein concentrate (WPC), as it promotes lipoprotein complex formation following a decrease in pH and ionic strength. The aim of this work was to study the impact of dilution factor (without dilution, with a 2X, 4X and 6X dilution) after EDBM on the process performances. For both products, a 4X dilution, which corresponds to a decrease in ionic strength of 81.4 ± 1.5 % for sweet whey and 79.4 ± 0.4 % for WPC, seemed sufficient to maximize lipoprotein complex formation as a plateau was reached in the defatting rates. Furthermore, it was demonstrated that the process could be used to recover PLs. Higher PL contents were found in the precipitates recovered from sweet whey combined with a dilution: highest contents in total PLs for WPC (7.45 ± 0.49 and 8.00 ± 0.49 g/100g with a 4X-6X dilution) were not different from the lowest content for sweet whey (7.50 ± 1.18 g/100 g without dilution). For both products, the main PLs recovered were phosphatidylethanolamine and phosphatidylserine, which respectively represented between 42.0 ± 1.7 and 51.6 ± 2.3 % and 30.1 ± 2.2 to 38.7 ± 0.8 % of total PLs. Furthermore, considering their high ecoefficiency scores, sweet whey combined with a 2X or 4X dilution are the most promising conditions.

Production of lithium hydroxide by electrodialysis with bipolar membranes

• LiOH (2.2 M) and H 2 SO 4 (1.3 M) were successfully produced from Li 2 SO 4 (1.5 M). • The specific energy consumption was estimated to be around 7 kWh/kg LiOH produced. • The LiOH purity was improved to 99.75%, by limiting the H 2 SO 4 concentration in the acid compartment. • Battery grade LiOH may be possible after only a small reduction of the sulfate content. In conventional lithium extraction processes, highly purified lithium sulfate is generated as an intermediate, which is transformed into lithium hydroxide for lithium-ion battery applications. This study illustrates the technical feasibility of converting the pre-purified lithium sulfate (Li 2 SO 4 ) into lithium hydroxide (LiOH) and sulfuric acid (H 2 SO 4 ) using an electrodialysis with bipolar membrane (EDBM) process. A feed solution of 1.5 mol/L Li 2 SO 4 is converted into 2.2 mol/L LiOH and 1.3 mol/L H 2 SO 4 with a specific energy consumption of less than 10 kWh/kg LiOH produced. Due to the increased acid and base volume caused by electroosmosis, both acid and base concentrations are lower than that estimated based on stoichiometry. Increasing the initial LiOH solution concentration decreases the sulfate transfer from the acid and feed solutions to the base solution. Maintaining a low concentration of H 2 SO 4 in the acid compartment (0.05 mol/L) significantly reduces the migration flux of sulfate ions through the bipolar membrane, leading to a LiOH purity of ~99.75%. This also lowers the energy consumption to ~7 kWh/kg, with a reduced average sulfate leakage flux into the base solution (~0.008 mol/m 2 hr). Battery grade LiOH could be obtained after a small further reduction of the sulfate content. This work demonstrates that EDBM can potentially replace the current chemical precipitation technique to produce LiOH from Li 2 SO 4 , by eliminating the use of a large quantity of alkali and the associated precipitation and solid–liquid separation steps.

Impact of conductivity on the performances of electro-acidification and enzymatic hydrolysis phases of bovine hemoglobin by electrodialysis with bipolar membranes for the production of bioactive peptides

Production of bioactive peptides from slaughterhouse wastes with a final low salt content by electrodialysis with bipolar membranes (EDBM) has recently been demonstrated as an innovative and efficient technology. However, a limitation in the electro-acidification process was noticed due to membrane fouling. In this context, the aim of the present work was to identify process conditions that could reduce peptide fouling in EDBM. Hence, two different conductivity levels (0.9 mS/cm and 4.5 mS/cm) were investigated in bipolar/monopolar (anionic and cationic) configuration and compared to conventional hydrolysis in the same conductivity conditions as well as a conventional hydrolysis using a buffer solution. The impact of such conductivity levels was studied during EDBM especially on membrane fouling and hydrolysis parameters: 1) kinetics of the enzymatic mechanism, 2) degree of hydrolysis and 3) peptide population. The results showed the same enzymatic mechanism “one-by-one” for all the conditions but a slower enzymatic kinetics for EDBM-0.9 mS/cm. EDBM-0.9 mS/cm allowed the production of bioactive peptides but with fouling formation on MCP while EDBM-4.5 mS/cm allowed the production of bioactive peptides without any fouling. Finally, optimizing certain conditions for further studies would lead to a promising green process to substitute synthetic additives used to protect food by antimicrobial peptides from blood slaughterhouses.