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Many researchers are interested in utilizing renewable and sustainable energy made by exoelectrogenic bacteria during electrodialysis for the separation of minerals and organic matters from aqueous environments. The aim of this study was to develop a novel thermophilic fermenter and dual anion exchange membrane bioelectrochemical system for separating biohydrogen production inhibitors from the thermophilic fermenter and thereby increasing biological and cathodic hydrogen production by food waste and wastewater. • Using this innovative system the biohydrogen production inhibitors were separated and nutrients (for example ammonium), alkalinity, buffering capacity and pH were preserved in the bioreactor at the same time, led to higher biological and cathodic hydrogen production.

A kinetic model of the bipolar electrodialysis process with a two-chamber unit cell formed by a bilayer (bipolar or asymmetric bipolar) and cation-exchange membrane is proposed. The model allows describing various processes: pH adjustment of strong electrolyte solutions, the conversion of a salt of a weak acid, pH adjustment of a mixture of strong and weak electrolytes. The model considers the non-ideal selectivity of the bilayer membrane, as well as the competitive transfer of cations (hydrogen and sodium ions) through the cation-exchange membrane. Analytical expressions are obtained that describe the kinetic dependences of pH and concentration of ionic components in the desalination (acidification) compartment for various cases. Comparison of experimental data with calculations results show a good qualitative and, in some cases, quantitative agreement between experimental and calculated data. The model can be used to predict the performance of small bipolar membrane electrodialysis modules designed for pH adjustment processes.

The influence of the nature of amine solutions on the frequency spectrum of the electrochemical impedance of the bipolar membrane aMB-2m is investigated. Moreover, the effect of the circulation rate of solutions in the electrodialyzer chambers on the volt-ampere characteristics of the Ralex AMH and MA-40L anion-exchange membranes and the aMB-2m bipolar membrane has been investigated. The diffusion characteristics of various types of anion-exchange membranes in a system containing dimethylammonium sulfate ((DEA)2H2SO4), as well as the diffusion characteristics of the Ralex AMH membrane in systems with methylammonium sulfate, dimethylammonium sulfate, diethylammonium sulfate, and ethylenediammonium sulfate ((MA)2H2SO4, (DMA)2H2SO4, (DEA)2H2SO4, EDAH2SO4) have been studied. It is shown that diffusion permeability depends on the structure and composition of anion-exchange membranes, as well as on the nature of amines. The technical and economic characteristics of the electromembrane processes for the production of amines and sulfuric acid from amine salts are determined. It is shown that when using Ralex AMH anion-exchange membranes in an electrodialyzer together with bipolar aMB-2m membranes, higher concentrations of diethylamine and sulfuric acid are achieved, compared with the use of MA-40L anion-exchange membranes.

Sodium hydroxide is produced mainly by the electrolysis of an aqueous solution of sodium chloride using mercury, diaphragm and membrane technologies. The membrane cell gained greater importance in recent years due to its environmental advantages and lower energy consumption. In this work, electrodialysis equipment has been built on a laboratory scale, using cation exchange membrane and anion exchange membrane, the effect of the operating conditions of the electrodialysis module on the concentration of hydrochloric acid and sodium hydroxide has been studied. The experimental results show that 15 volts are the most suitable operating condition, initial acid and base concentration of 0.05N and sodium chloride concentration of 50 g/L. reaching a hydrochloric acid concentration of 0.22N and 0.25N of sodium hydroxide, respectively, during 210 minutes of operation of the electrodialysis module. The energy consumption was 14.9kWh/Kg of sodium hydroxide and the current efficiency of 53.5%. The process offers the advantage of using clean technology compared to traditional processes for acid and base production. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The electromembrane process for production of naphthenic acids is proposed. • The BPM-C-C ED stack shows stable characteristics in the presence of naphthenate ions. • Conversion of sodium naphthenate is complicated by micelle formation in solution. • Ways to counter the negative effects of micellation are provided. Abstract The process of recovery of sodium naphtenates into naphtenic acids and sodium alkali using electrodialysis with bipolar membranes is investigated. A membrane stack of an electrodialyzer with a three-chamber unit cell in which the salt chamber is formed by two cation-exchange membranes is proposed, which eliminates the transfer of anions from the salt chamber to an adjacent alkaline and acidic one. The values of current efficiency for naphtenic acid and alkali, as well as energy consumption for the process, are determined. It is shown that the main problems with the development of electro-membrane technology for producing naphtenic acids from petroleum and petroleum products are associated with micelle formation of a mixture of naphtenic acids with sodium naphtenate in the pH = 6.5–8 range, which leads to a sharp increase in the viscosity and electrical resistance of solutions. Introduction of the cation-exchanger and sodium sulfate to the intermembrane space of naphtenthe salt chamber can significantly improve the technical and economic characteristics of the process - for example, the specific energy consumption decrease from 0.86 kW h·L−1 down 0.38 kW h·L−1, which is more than two times lower than the original three-chamber cell. At the same time, the production of naphtenic acids remains on the same level which is 17 L·m−2·h−1. [ABSTRACT FROM AUTHOR]

Complex streams in bio‐based industries require efficient downstream processing units. Simulated moving‐bed (SMB) chromatography is known to improve process efficiency by reducing resin and buffer requirement, but it can be further enhanced by technology hybridization. In the current experiments, an SMB system has been integrated with a bipolar electrodialysis (BPED) system. SMB purified γ‐aminobutyric acid (GABA) from a clarified fermentation broth while BPED processed the product‐containing eluent stream into recyclable eluent and purified product streams. The continuous operation did not result in any impurity accumulation. Effective donwnstream processing units are mandatory for complex streams in bio‐based industries. Simulated moving‐bed chromatography can improve process efficiency by reducing resin and buffer requirement and be further enhanced by hybridization. Such system was successfully integrated with bipolar electrodialysis for purification of γ‐aminobutyric acid from a clarified fermentation broth. [ABSTRACT FROM AUTHOR]

The paper presents the results of tests of an electromembrane installation for the complex processing of a technological solution formed in the production of para-aramid fibers. The installation consists of two main units and three different electrodialysers, each of which performs its specific function. Electrodialysis with bipolar membranes is designed to produce lithium hydroxide, a conventional electrodialysis module is designed for preliminary treatment of the technological solution and its preconcentration and electrodialysis with ion-exchange resin serves for finishing cleaning and complete removal of ionic impurities from the solution. Optimum parameters of the process were chosen, which allows processing 6.3 m 3 of technological solution per day. The total operating time of the installation during the tests was 770 h. The main specific characteristics of the process of obtaining lithium hydroxide by electrodialysis with bipolar membranes from technological solutions with a mass fraction of organic components ranging from 1.8 to 59% are determined. The average current efficiency in solutions with different contents of organic components were 0.6; the specific productivity for lithium hydroxide decreases from 5.7 to 2.1 mol × m −2 × h −1 with an increase in the proportion of organic solvents. The combination of conventional and ion-exchange electrodialysis allows obtaining a pure water-organic mixture with a current yield of no less than 0.4. During the entire operation of the plant, no signs of degradation of the ion-exchange membranes used and deterioration of the installation operation have been detected. [ABSTRACT FROM AUTHOR]

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 SO 4 2− with energy consumption of 2.7–3 kWh/kgH 2 SO 4. 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. [Display omitted] • ED and NF were used to recycle nutrients from a spent culture broth. • Recycled nutrients were successfully reused in the batch fermentation. • Sulfuric acid (∼0.13 M) successfully recovered from the spent culture broth by EDBM. • Cultivation with recovered acid had improved growth curve than reference medium. • NF was less energy-consuming but ED/EDBM offered target-specific ion recovery. [ABSTRACT FROM AUTHOR]

Separation of fumaric acid from fermentation broth was carried out by bipolar electrodialysis using a laboratory ED set-up with an effective membrane stack area of 64 cm 2 . The limiting current density was calculated on the basis of experimental current–voltage curves and optimal conditions of the process performance were proposed. Bipolar electrodialysis of post-fermentation broth from biotechnological conversion of glycerol was preceded by preliminary experiments regarding monocomponent, binary and ternary model solutions of fumaric acid. The influence of current density, pH and composition of fumaric acid model solutions on the efficiency of the process was analysed and discussed. Results of this report have proven that bipolar electrodialysis can be used as one of the purification steps towards recovery of fumaric acid from fermentation broth. [ABSTRACT FROM AUTHOR]

A novel approach based on a hybrid system allowing nanofiltration, bipolar electrodialysis and reactive extraction, was proposed to remove fumaric acid from fermentation broth left after bioconversion of glycerol. The fumaric salts can be concentrated in the nanofiltration process to a high yield (80-95% depending on pressure), fumaric acid can be selectively separated from other fermentation components, as well as sodium fumarate can be conversed into the acid form in bipolar electrodialysis process (stack consists of bipolar and anion-exchange membranes). Reactive extraction with quaternary ammonium chloride (Aliquat 336) or alkylphosphine oxides (Cyanex 923) solutions (yield between 60% and 98%) was applied as the final step for fumaric acid recovery from aqueous streams after the membrane techniques. The hybrid system permitting nanofiltration, bipolar electrodialysis and reactive extraction was found effective for recovery of fumaric acid from the fermentation broth. [ABSTRACT FROM AUTHOR]

Highlights: [•] NF and EDBM were applied to separate and concentrate fumaric acid from fermentation broth. [•] The influence of electrodialysis stack configuration on the efficiency of EDBM process was analysed. [•] The retention of fumaric acid in NF process increased strongly with increasing pH of initial solution. [Copyright &y& Elsevier]

Highlights: [•] An ionic liquid was used as a solvent to improve electrodialysis technology. [•] Sodium butyrate was our model organic salt for current transport. [•] Both electrodialysis and bipolar electrodialysis were tested with ionic liquids. [•] Ion transport occurred into the ionic liquid from an aqueous solution. [•] Ionic liquids showed potential to reduce product separation energy and cost requirements. [Copyright &y& Elsevier]

The application of bipolar electrodialysis (BPED) for the simultaneous removal of inhibitory acetate and pH control during E. coli fermentation was investigated. A two cell pair electrodialysis module, consisting of cation exchange, anion exchange and bipolar membranes with working area of 100 cm2 each, was integrated with a standard 7 l stirred tank bioreactor. Results showed that BPED was beneficial in terms of in situ removal of inhibitory acetate and a reduction in the amount NH4OH used for pH control. In batch and fed-batch BPED fermentations, base additions were decreased by up to 50% in both cases compared to electrodialysis (ED) fermentations with pH controlled at 6.7 ± 0.1. Consequently, the final biomass (34.2 g DCW l−1) and recombinant protein (5.5 g l−1) concentrations obtained were increased by up to 37 and 20%, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Electrodialysis (ED) using two-stack configurations with homopolar or bipolar membranes was investigated for deacidification of tropical fruit juices (passion fruit, mulberry, naranjilla). The objective was to develop a mathematical treatment for ED to predict the behavior of a fruit juice at industrial scale from ED performances at laboratory scale. From parameters such as current efficiency, electric resistance of the anion exchange membrane, and coefficients of variation with temperature determined in a laboratory-scale stack, modeling was applied to a pilot-scale stack that has a total effective membrane area 70 times larger. If no fouling took place, and except for conductivity at pH higher than 3.8, the differences between the experimental and simulated values for pH, titrable acidity, voltage, and energy consumption were inferior to 7%, 16%, 20%, and 15%, respectively, for all the fruit juices and operating conditions. Moreover, the average electrical charge of citric acid species transferred was 2.16 for all fruit juices, indicating that the current transport was mainly due to the ionic species issued from the secondary dissociation of the citric acid. [Copyright &y& Elsevier]

Abstract: The reduction of acidity of passion fruit juice was investigated by electrodialysis (ED) with bipolar membranes (BM) at the laboratory and pre-industrial scale. Four states of juice were tested: initial pulpy juice, juice clarified by tangential microfiltration, twice-concentrated clarified juice, centrifuged juice. The ED performances were compared in terms of deacidification rate, current efficiency, and energy consumption. The deacidification was carried out up to pH 4.5 with satisfactory results. ED performances were lower with the pulpy and concentrated juices because of fouling of the anion-exchange membrane, which increased voltage. The differences in acidity between the juices was reduced by the pre-industrial ED stack, which involved better hydrodynamics through high flow rates and low compartment thickness. Whatever the juices, physico-chemical analysis showed that colour changed only slightly. [Copyright &y& Elsevier]

The efficiency of bipolar electrodialysis (BED) for the recovery of lactic acid from fermentation broth was evaluated. Three systems of BED (bipolar-anion, bipolar-cation and bipolar-anion-cation) at fixed voltage (20 V) were compared using a model solution of ammonium lactate (100 g l−1). Results showed that bipolar-anion (BED-anion) was the most beneficial in terms of lactate flux, current efficiency, energy consumption and recovery ratio. Consequently, BED-anion was used to purify lactic acid from fermentation broth which had been pre-treated with mono-polar electrodialysis (MED). The final lactic acid concentration and lactate flux obtained were 144 g l−1 and 393 g m−2 h−1, respectively. Using the two-step process (MED and BED-anion) the concentration of fermentation broth was increased by 33% and the total energy consumption was 2.76 kW h kg−1. [ABSTRACT FROM AUTHOR]

Abstract: The reduction of acidity of four tropical fruit juices, passion fruit, castilla mulberry, najanrilla and araza, was investigated by using the electrodialysis (ED) process. Two stack configurations using homopolar membranes and three compartments (ED3C), and bipolar membranes and two compartments (EDBM2C), were tested at the laboratory and pre-industrial scale. The ED performances were evaluated as a function of operating conditions such as current density, flow rate, temperature and final pH of the deacidification. The passion fruit, mulberry and naranjilla juices whose acidity is mainly due to the citric acid, had a similar behaviour. A fouling membrane took place in some operating conditions. It is particularly significant with the mulberry juice probably because of its high content in phenolic compounds. Lower ED performances were obtained with the araza juice whose acidity is mainly due to the malic acid. The deacidification was carried out until pH 4, 4.5 or 7.9 with satisfactory results in all cases. Comparing the two ED configurations, ED3C gave better performances than EDBM2C. Nevertheless, the latter configuration allowed the production of the citric or malic acid, and avoided the NaOH consumption induced by ED3C. The use of a pre-industrial pilot with a membrane area 10 times greater and a thickness compartment 13 times lower than the laboratory cell induced a significant decrease in the energy consumption, by 70% and 60%, for ED3C and EDBM2C, respectively. [Copyright &y& Elsevier]

Abstract: The studies of acid purification and base purification via bipolar electrodialysis are presented. The process of acid recovery involved spent solutions of acid (HCl or H2SO4) and iron salt obtained in the course of conventional electrodialysis. Bipolar electrodialysis yielded an acid solution concentrated 51-fold (in the case of hydrochloric acid) and 63-fold (in the case of sulphuric acid) as compared to the feeding solution for conventional electrodialysis. The solution of the recovered acid was only slightly contaminated with iron salt (0.12 and 0.13%). The process of base purification yielded an NaOH solution concentrated nine-fold as compared to the feeding solution for the bipolar electrodialysis process. The contamination of the recovered base varied from 1.75 to 2.50%. [Copyright &y& Elsevier]

The high acidity of passion fruit limits its addition in food preparation. In order to easy the uses of this juice to formulate high aroma and flavour products, its citric acid content must be decreased. Various methods such as calcium salts precipitation, ion-exchange resins and electrodialysis with homopolar and bipolar membranes were investigated to increase the pH of a clarified passion fruit juice from 2.9 to 4.0. Each deacidification process was compared in terms of characteristics of deacidified juices such as concentration of inorganic and organic ions, colour and flavour. The deacidification by precipitation using CaCO3 was not recommended because of CO2 release. The ion-exchange process gave a poor quality juice in terms of organoleptic characteristics. Electrodialysis with homopolar membranes induced an increase in the sodium concentration. Precipitation with Ca(OH)2 and electrodialysis with bipolar membrane were the most suitable processes in terms of sensorial properties of juices treated. The physico-chemical analyses showed an increase in the calcium concentration with the use of Ca(OH)2 that could cause some precipitation problems in the final product. Inorganic anions were eliminated together with citrate by using electrodialysis and resins. Nevertheless, electrodialysis with bipolar membranes presented great advantages: it was a continuous process without reagent addition moreover allowing the production of a valuable solution of citric acid. [Copyright &y& Elsevier]

• The EDBM process allows almost total removal of AKG from the broth. • AKG separation and simultaneous conversion to its acidic form. • The low initial pH of diluate solution reduces the scaling phenomena. • Initial techno-economic analysis showed low total recovery costs for AKG. In this study bipolar membrane electrodialysis (EDBM) was used in the main process of separation of bio-based alpha-ketoglutaric acid from actual post-fermentation broth. In the first part of this study, simulated broths were used to determine the optimum duration of EDBM process. The effect of pre-treatment of actual post-fermentation broth on EBDM process was also investigated. Simultaneous effective separation of alpha-ketoglutarate from the actual post-fermentation broth (after pre-treatment procedure) and conversion to alpha-ketoglutaric acid form were carried out. The results presented in this paper indicate that the applied EDBM process allows almost total removal of alpha-ketoglutarate from actual post-fermentation broth with high current efficiency (64 %) and low energy consumption (1.1 kW h/kg). Furthermore, the low initial pH (2.4–2.7) of diluate solution inhibits the migration of lactate and acetate through the anion exchange membrane and reduces the scaling phenomena. Preliminary costs analysis of the electrodialytic recovery of AKG from fermentation broth (including the energy as well as fixed cost) showed that the total fixed cost per 1 kg of AKG was low and about 1.2$. [ABSTRACT FROM AUTHOR]

• The process of electrodialysis concentration of inorganic salts and acids was studied. • For salt solutions CE and hydration number determine maximum concentration. • For acid solutions, the main factor that limits concentration is osmosis of water. • The two-stage scheme (BMED and EDC) can be used to produce sulfuric acid. The electrodialysis concentration process of sodium chloride, sodium sulfate, lithium chloride, ammonium nitrate, sulfuric and nitric acids were studied. Using the model of electrodialysis concentration, the transport coefficients of the Ralex CM-PP/Ralex AMH-PP membrane pair were calculated. It has been established that for salt solutions, the key factors determining the maximum attainable electrolyte concentration in the concentration chamber are the electromigration current efficiency and the hydration number of the electrolyte. For acid solutions, the most important factors determining their concentration are the osmotic and electroosmotic transport of water through the membrane. Besides, it was found that in the process of electrodialysis concentration of acids, proton leakage occurs through the strongly basic anion-exchange membrane from the concentration chamber to the desalination chamber, which significantly reduces the current efficiency. To obtain concentrated solutions of sulfuric acid with a low content of salt ions, a two-stage scheme for the recovery of the sodium sulfate into sulfuric acid using bipolar electrodialysis (BMED) and an electrodialyzer-concentrator (EDC) is proposed. A two-stage process, including BMED and EDC, for the conversion of sodium sulfate into sulfuric acid allows one to obtain acid with a concentration of up to 1.52 M by sulfate ion with a content of sodium ions of not more than 0.005 M. At a reasonable current density of 2 A/dm2 the obtained concentration of acid was 1.16 M by sulfate ion with current efficiency of 0.89 for BMED and 0.26 for EDC, total specific energy consumption of 0.83 kWh/mol SO 4 2-, and acid flux of 0.024 mol SO 4 2-·dm−2·h−1 (0.23 kg H 2 SO 4 ·m−2·h−1). The obtained specific characteristics of the process are comparable with the characteristics of bipolar electrodialysis using industrial bipolar membranes. [ABSTRACT FROM AUTHOR]