Bipolar Membrane Electrodialysis Research Articles

Bipolar membrane electrodialysis integrated with in-situ CO2 absorption for simulated seawater concentrate utilization, carbon storage and production of sodium carbonate

In the context of carbon capture, utilization, and storage, the high-value utilization of carbon storage presents a significant challenge. To address this challenge, this study employed the bipolar membrane electrodialysis integrated with carbon utilization technology to prepare Na2CO3 products using simulated seawater concentrate, achieving simultaneous saline wastewater utilization, carbon storage and high-value production of Na2CO3. The effects of various factors, including concentration of simulated seawater concentrate, current density, CO2 aeration rate, and circulating flow rate of alkali chamber, on the quality of Na2CO3 product, carbon sequestration rate, and energy consumption were investigated. Under the optimal condition, the CO32– concentration in the alkaline chamber reached a maximum of 0.817 mol/L with 98 mol% purity. The resulting carbon fixation rate was 70.50%, with energy consumption for carbon sequestration and product production of 5.7 kWhr/m3 CO2 and 1237.8 kWhr/ton Na2CO3, respectively. This coupling design provides a triple-win outcome promoting waste reduction and efficient utilization of resources.

Amine-promoted gypsum carbonation for efficient CO2 capture and selective synthesis of CaCO3 polymorph integrating with amine regeneration by bipolar membrane electrodialysis

CO2 mineralization of waste gypsum not only reduces the carbon emissions of power plants but also improves gypsum utilization by recovering high-value-added CaCO3. However, the extensive consumption of various reagents limited its development. This paper proposed an amine-promoted waste gypsum carbonation process integrating with amine regeneration by bipolar membrane electrodialysis (BMED). The alkaline amine was expected to act as a multifunctional reagent for gypsum carbonation — alkaline reagent, CO2 absorbent, gypsum dissolution promoter, and CaCO3 crystal regulator. Seven typical amines with different amino types and pKa values were selected to investigate the feasibility of this process. Results show that promising CO2 removal efficiency (>95 %) from an artificial exhausting gas, gypsum carbonation efficiency (>93 %), and CO2 sequestration capacity (>340 g-CO2/kg-gypsum) can be achieved due to the additional alkalinity, fast CO2 absorption, high CO2 concentrations, and enhanced CaSO4 dissolution in amine solutions. In addition, the interactions of amine-CO2-gypsum and the CaCO3 growth mechanism in the gas–liquid-solid system were explored. Monoethanolamine (MEA), 3-amino-1-propanol (MPA), piperazine (PZ), and 1,3-Diaminopropane (DAP) could prolong the CaCO3 precipitation due to their strong affinity for Ca2+ and CO32−. In this case, CO2 absorption by the liquid phase dominated the carbonation process in the initial 30 min for these four amines, while CaCO3 precipitation mainly occurred within 30 ∼ 120 min. Amines’ different affinities for Ca2+ and CO32− provided an approach to selective synthesis of CaCO3 polymorph: 100 % calcite by PZ, 100 % vaterite by DAP, a calcite-vaterite mixture by MEA, and a calcite-vaterite-aragonite mixture by MPA. After the carbonation process, amines were recycled from the liquid residue by BMED, which could provide OH− for amines regeneration from protonated amines, recovery of H2SO4, and decrease the solution salinity.

Nutrient recovery as struvite from aquaculture wastewater by bipolar membrane electrodialysis with magnesite tailings

In this study, the feasibility of simultaneously recovering Mg, nitrogen (NH4-N) and phosphorus (P) from magnesite tailings and freshwater aquaculture have been confirmed through the bipolar membrane electrodialysis with a processing unit for the first time. The H+ required for Mg2+ leaching and OH– needed for struvite formation can be provided by the BMED system. The results indicate that adding 0.3 mol/L initial HNO3 could enhance the Mg2+ leaching and reduce the energy consumption (EC). The recovery ratios of P and NH4-N reached to about 97.9 % and 52.3 %, respectively, while the EC was about 0.051 kWh/L. Increasing the tailing dosage shortened the required treatment time and reduced the EC. Increasing the current density significantly enhanced nutrient recovery rate, but accompanied by an increase in EC. A longer treatment time is necessary for treating larger volumes of wastewater, while a P recovery ratio of approximately 99 % can be achieved. Calcium is the predominant impurity. The purity of struvite was enhanced through a multi-batch process, achieving a maximum of 97.1 % at the third time. This study provides new insights into the resourceful treatment of tailings and wastewater.

Removal and recovery of deep eutectic solvent with membrane-based methodology: A promising strategy to enhance extraction and purification of Dendrobium officinale flavonoids

Finding efficient, environmental friendly extraction and purification methods of natural active substances has always been a research hotspot in the field of food. In this study, the yield (36.76 ± 2.17 mg/g) of Dendrobium officinale flavonoids (DOFs) was significantly increased by ultrasonic-assisted deep eutectic solvent (DES) method. DES was removed and recovered from the Dendrobium officinale extracts by bipolar membrane electrodialysis (BME). At 70 V, the removal ratios of choline chloride (ChCl) and lactic acid (Lac) could reach 92 % and 90 %, and DOFs were further enriched. Then, Dendrobium officinale polysaccharides (DOPs) was effectively separated from DOFs component using ultrafiltration (UF). After BME-UF treatment, the purification efficiency of DOFs by macroporous resin (MR) was increased by 2.1 times. UPLC-Triple-TOF/MS results further confirmed that, the content of DOFs was increased by 59 times after purification. This study suggested that BME-UF was a valid method for purification of flavonoids, which also promoted green extraction.

Fabrication of efficient bipolar membranes with functionalized MOF interfacial layer for generation of various carboxylic acids via electrodialysis

Stability and compatibility of two layers with each other are the major drawback of the bipolar membrane (BPM). Sulfonated poly (ether ether ketone) and quaternized poly phenylene oxide are taken as the cation exchange layer (CEL) and anion exchange layer (AEL) respectively to fabricate the bipolar membrane by layer-by-layer assembly. Different functionalized MOF (MIL-101 Cr) are prepared for the interfacial layer (IL) of BPM as water dissociation (WD) catalysts. Various analytical techniques (XRD, FT-IR, SEM, BET, XPS, TGA) are used to examine the chemical structure, textural properties and thermal stability of the synthesized catalysts. Two different catalytic sites of MOF as inorganic metal-ion and organic ligands facilitates the water dissociation rate. The effect of different IL (functionalized MOF) on performance of BPM is studied for the dissociation of NaCl into corresponding acid and alkali. BPM with bi-functionalized MOF as IL (BPM-BMOF) shows the better electro-chemical and physicochemical properties in term of ionic conductivity (8.02 mS cm−1) with 38.1 % water uptake, among the synthesized BPMs. The performance of BPM-BMOF is evaluated for the generation of different organic carboxylic acids from sodium carboxylates using bipolar membrane electrodialysis (BPMED). BPM-BMOF shows the 94.12 % acid generation with 0.496 g h−1 water dissociation rate using 0.2 M NaCl feed solution. The results suggest that product recovery (PR) and energy efficiency (ƞ) gradually reduces with higher homologous of sodium carboxylates under similar experimental conditions. The performance of BPM-BMOF with negligible co-ion leakage and stability made it industrially applicable for water splitting.

Evaluating the potential of semi-continuous itaconic acid fermentation by Aspergillus terreus: operational profile and experiences

Itaconic acid is an important bio-based chemical. The present study aims to evaluate the applicability of semi-continuous fermentation technique for itaconic acid production by Aspergillus terreus. The fermentation is planned to be connected with bipolar membrane electrodialysis unit for acid recovery. This process allows the reuse of residual glucose from the effluent. Our particular attention was focused on the effect of glucose concentration. Two different glucose supplementation strategies were tested: constant glucose concentration in the refilling medium and adjusted glucose concentration in order to maintain a continuously high – 120 g/L – glucose concentration in the fermentor. The itaconic acid titre, yield and productivity for the 24 h time periods between draining/refilling interventions were investigated. The constantly high glucose concentration in the fermentor resulted in doubled biomass formation. The average itaconic acid titre was 32.9 ± 2.7 g/L. The producing strain formed numerous spores during semi-continuous fermentation that germinated continuously. Yield and volumetric productivity showed a periodic pattern during the procedure.

Construction of integrated model of bipolar membrane electrodialysis membrane process and gas absorption-ion reaction process

The bipolar membrane electrodialysis (BMED) possesses the capability of green and efficient recovery of salt resources and alkali production, making it suitable for coupling with seawater utilization and CO2 absorption-mineralization processes. In order to reveal the process control mechanism and dynamic equilibrium, the imperative arises to construct a transport-reaction differential model. The overall process is subdivided into distinct modules: mass transport, reaction, electrical, and tank, with the aim of streamlining this intricate coupling procedure. Based on the Nernst-Planck model and combined with semi-empirical models, the models for each module were constructed, and differential equations were used for model integration. This approach addresses the complexity of multiphase reactions and mass transport processes that are challenging to describe through mathematical models. This model can predict indicators such as decalcification rate, carbon fixation rate, and energy consumption, and the accuracy of these results under various conditions was thoroughly verified through experimental data. This study is expected to provide guidance for the modeling of membrane process coupling.

Investigation of the effect of impurity concentration in the simulated industrial saline water on the scaling phenomenon on ion exchange membranes

One of the most critical problems to be solved in membrane separation processes is the fouling of membranes. Fouling causes a reduction in current efficiency in processes using ion-exchange membranes. In this study, the mechanism of fouling on the anion exchange membrane, cation exchange membrane, and bipolar membranes caused by impurities such as CaCl2, MgCl2, Na2CO3, and NaHCO3 in the electrodialysis process of the feed solution containing NH4Cl and NaCl as the main components were investigated. The effects of initial impurity concentration on bipolar membrane electrodialysis stack resistance, demineralization, ion flux, acid and base conversion, and concentration of produced acid and base were investigated. SEM-EDX, XRD, FTIR, and TGA analyses were used for membrane characterization. Chemical cleaning was done to remove impurities in the membrane and spacer structure. The effects of chemical cleaning on cell performance were determined by comparing the process performances before and after cleaning. Experimental results showed that ions such as Ca2+ and Mg2+ in the feed solution cause precipitate on the cation exchange membrane and spacers in the base compartment. The results revealed that these precipitates do not cause structural damage to the membranes but affect their performance.

Bipolar membrane electrodialysis: A promising paradigm for caustic soda production

AbstractCurrently, a supply‐demand imbalance between NaOH and Cl2 in the chlor‐alkali process places a great burden on the environment. Bipolar membrane electrodialysis (BMED) is a competitive technology to produce acid and base due to its water splitting characteristics. To determine the competitiveness of NaOH production between BMED and the chlor‐alkali method, BMED was evaluated at various current densities with different NaCl concentrations. Results show that NaOH energy consumption in BMED is less than that of the chlor‐alkali method at a moderate salt concentration (<9 wt.%). Interestingly, the stack voltage suddenly increases during the later stage of BMED. It is speculated that the high osmotic pressure surrounding bipolar membranes restrains water transport into the interfacial layer. In addition, economic assessment indicates that BMED has less impact on global warming than the chlor‐alkali process. Overall, the BMED technique is a promising paradigm for base production in an economical and sustainable manner.

Treatment of carbocysteine wastewater by bipolar membrane electrodialysis: From lab-to pilot-scale

Carbocysteine (H2ccys) wastewater, which contains H2ccys, chloroacetic acid, and ammonium chloride, can pose significant risks to the environment. In this study, a novel strategy was proposed for treating H2ccys wastewater by bipolar membrane electrodialysis (BMED) to realize resource recovery. The migration and coexistence mechanism of organic/inorganic ions in wastewater were investigated in lab-scale experiments. The results indicated that the desirable migration of inorganic ions, such as NH4+ and Cl− ions, in the feed compartment were dominant. The undesirable migration of organic molecules, such as ClCH2COOH and H2ccys, could be managed through precise control of the BMED reaction process. To optimize the energy efficiency and thermal effect occurred in the pilot-scale, a two-stage BMED process was designed for treating H2ccys wastewater. The results revealed that BMED produced 1.33–1.63 M of HCl and 2.62–2.88 M of NH3·H2O, and removed 90 wt% of NH4Cl from H2ccys wastewater. Meanwhile, the thermal effect of the slot at the outermost acid compartment decreased from 3.32 W in the one-stage BMED process to 0.10 W in the two-stage BMED process during the pilot-scale tests. The current efficiency of the two-stage BMED process for the acid/base production and feed desalination in the pilot-scale tests increased and its energy consumption decreased compared with the lab-scale tests. Moreover, the BMED rrecycling route showed that a closed loop can be realized in the treatment of H2ccys wastewater, and its economic assessment showed that applying BMED to the treatment of H2ccys wastewater have economic benefits. These findings illustrated the feasibility of this novel strategy for treating H2ccys wastewater and laid a solid foundation for its industrialization.

Performance evaluation on CO2 fixation with chlorine gas production based on direct electrolysis of seawater

CO2 fixation from seawater is an effective way to mitigate climate change and has gained widespread attention in recent years. However, the existing research mostly involves stoichiometric bases and bipolar membrane electrodialysis methods, and the performance of direct seawater electrolysis for CO2 fixation is presented with limited studies and rare research data. The performance evaluation on CO2 fixation based on the technology of direct seawater electrolysis is presented in this paper. Energy consumption, decalcification rate, and calcium carbonate production rate are employed as performance indexes to assess the feasibility of CO2 fixation through direct electrolysis of seawater. The simulation method is adopted in this paper, with validation based on data from experiment. As a result, the minimum energy consumption for per amount of calcium carbonate deposited ranges from 557.82 to 730.06 kJ/mol CaCO3 at the seawater flow rate range of 0.01–0.1 L/s, which has an advantage over other electrochemical CO2 capture method. Additionally, the decalcification rate and calcium carbonate production rate can reach a maximum of 100% and 0.36 mmol/s respectively. The conclusions presented in this paper can serve as a valuable guide for conducting large-scale evaluations or application analyses.

E-Chem Education: A Crash Course in Electrochemical Engineering for Caustic Soda Plant Design

The capstone chemical engineering senior process design course at Penn State in spring 2023 tasked students with designing a caustic soda process to partially meet the global demand for commoditized sodium hydroxide. This article disseminates our experience teaching senior chemical engineering students the core tenets of electrochemical engineering in a single class period for designing an electrolytic caustic soda process. In this E-Chem Education article, we relate key concepts found in chemical engineering (such as sizing up a reactor volume), which chemical engineering seniors are adept with, to electrochemical engineering principles (e.g., current density, voltage, and membrane electrode assembly area) for sizing up and costing out a chlor-alkali electrolyzer. Furthermore, we also discuss alternative electrolyzer designs outside the traditional chlor-alkali process, such as oxygen depolarized cathode (ODC) chlor-alkali and bipolar membrane electrodialysis (BPMED), for caustic soda production and the pros and cons of the alternative process designs.

Design and study of a novel ammonia‐based CO2 capture process with bipolar membrane electrodialysis

AbstractAqueous ammonia is a promising absorbent in the field of post combustion CO2 capture. However, the high volatilization of NH3 results in a high energy requirement, as well as solid precipitation during the CO2 regeneration process. A novel process was designed to reduce energy consumption and solve the problem. The bipolar membrane electrodialysis (EDBM) unit and CO2 regeneration reactor were taken as the regeneration part. In the novel process, the bubble in the EDBM unit would be eliminated, and the regeneration of CO2 and aqueous ammonia would be operated separately, which significantly reduced energy consumption and avoided the risk of precipitation during regeneration. According to the simulation and calculation results, the CO2 regeneration energy consumption of the novel process using H2SO4 for CO2 regeneration is 39.0% lower than that of the conventional ammonia‐based process, which shows good energy saving potential. Moreover, the novel process will be more competitive as membrane technology develops.

Utilizing Advanced Bipolar Membranes in Next Generation Electrodialysis Systems

Bipolar membrane electrodialysis (BPMED) is an essential process used in various industrial applications, such as water purification and acid/base production. Additionally, advanced BPMED systems are an integral component of larger CO2 sequestration technologies, allowing for ease of pH control within these systems. Improving these systems is vital to mitigating the global effects of climate change. To develop a viable advanced BPMED scheme, it is necessary to acquire bipolar membranes (BPMs) that operate at minimal voltage loss, high current density, and exhibit little ion crossover, while maintaining high performance over an industrially adequate timeframe. Researchers, such as Oener et al., have advanced BPM designs with the introduction of metal oxide catalysts to the interface of the cation- and anion-exchange layers of the BPM. These advanced BPM have shown a significant reduction in the energetic requirements of water dissociation. Applying these findings to BPMED has the potential to significantly improve the efficiency of BPMED systems, however, the BPM electrolyzer used for the development of these BPM are not directly analogous to an electrodialysis system. Thus, I present here a custom-built BPMED system that allows for the assessment of the specific voltage contributions of each component within the overall BPMED system. Using this tool, we aim to identify and address the performance and durability limitations of advanced BPM in BPMED by monitoring signs of degradation, such as blistering and delamination, and by monitoring changes in the potential drop across the BPM as conditions within the BPMED system are manipulated. This will lead to enhanced efficiencies and increased durability in BPMED applications, allowing for its integration into emerging CO2 sequestration systems, as well as other stacked membrane systems.

Electrochemically Mediated Ammonia Removal and Recovery from Wastewater Using Functional Membranes

Wastewater treatment plants (WWTPs) typically use anaerobic digestion (AD) to treat sludge, but ammonia produced during AD process returns to the headworks of WWTPs. The amount of ammonia in the liquid stream produced after dewatering the stabilized sludge, commonly referred to as dewatering sidestream, could contribute as high as 20% of the overall ammonia loading to WWTPs. Several sidestream treatment technologies are being developed not only to prevent additional ammonia inputs to WWTPs, but also to valorize ammonia for fertilizer production. Electrochemically mediated processes can achieve this goal in two simultaneous steps: (1) ammonium separation from wastewater through a cation-exchange membrane and (2) ammonium-to-ammonia conversion for its recovery by membrane stripping. Although electrochemical reactions in electrodialysis or flow-electrode capacitive deionization have been shown to drive the separation and increase the solution pH, an acid solution must be externally fed in the subsequent stripping process. Here, we demonstrated the use of bipolar membrane electrodialysis (BMED) to separate ammonium while simultaneously producing acid and base streams. Using a three-compartment BMED cell (effective repeating unit area = 29.2 cm2) with a synthetic sidestream containing 50 mM total ammonia nitrogen (TAN), we achieved TAN removal up to 80% with energy consumption less than 10 kWh kg−1 N at a productivity of 34.2 L m−2-repeating unit membrane area h−1 (LMH). The separated ammonia was recovered (>90%) in a subsequent membrane contactor that was fed with acid and base streams produced from the BMED cell. We specifically focused on increasing TAN concentration in the final product stream by changing relative flow rate of acid/base streams, which allowed for concentrating TAN nearly 8 times greater than the feed. These results show the use of BMED coupled with membrane stripping enables ammonia recovery without the need for chemical inputs, representing a promising sidestream treatment technology.

Bipolar Membrane Electrodialysis for Direct Conversion of L-Ornithine Monohydrochloride to L-Ornithine.

In this study, bipolar membrane electrodialysis was proposed to directly convert L-ornithine monohydrochloride to L-ornithine. The stack configuration was optimized in the BP-A (BP, bipolar membrane; A, anion exchange membrane) configuration with the Cl- ion migration through the anion exchange membrane rather than the BP-A-C (C, cation exchange membrane) and the BP-C configurations with the L-ornithine+ ion migration through the cation exchange membrane. Both the conversion ratio and current efficiency follow BP-A > BP-A-C > BP-C, and the energy consumption follows BP-A < BP-A-C < BP-C. Additionally, the voltage drop across the membrane stack (two repeating units) and the feed concentration were optimized as 7.5 V and 0.50 mol/L, respectively, due to the low value of the sum of H+ ions leakage (from the acid compartment to the base compartment) and OH- ions migration (from the base compartment to the acid compartment) through the anion exchange membrane. As a result, high conversion ratio (96.1%), high current efficiency (95.5%) and low energy consumption (0.31 kWh/kg L-ornithine) can be achieved. Therefore, bipolar membrane electrodialysis is an efficient, low energy consumption and environmentally friendly method to directly convert L-ornithine monohydrochloride to L-ornithine.

One‐step conversion of sulfate lithium into high‐purity lithium hydroxide crystals via bipolar membrane crystallization

AbstractTo date, bipolar membrane electrodialysis (BMED) is being developed as a competitive technology for waste lithium‐ion battery recovery. However, the purity and concentration of lithium hydroxide generated from a BMED plant could not meet the product criteria for ternary lithium batteries, thus requiring additional condensation, purification, evaporation, and crystallization procedures. Herein, bipolar membrane crystallization (BMC) was proposed for the one‐step conversion of sulfate lithium into high‐purity lithium hydroxide monohydrate crystals. By mediating a continuous saturated feedstock in the salt compartment, it is possible to convert Li2SO4 into 5+ mol/L LiOH at a current density higher than 500 A/m2. Therefore, this unique design allows the production of 99.9% LiOH∙H2O by taking the principle of water dissociation in the bipolar membrane and the simultaneous crystallization procedure. This proof‐of‐concept study proves the feasibility and competitiveness of the BMC for waste lithium recovery by abandoning the condensation and evaporation procedures.

Techno-economic analysis of integrated bipolar membrane electrodialysis and batch reverse osmosis for water and chemical recovery from dairy wastewater

Bipolar membrane electrodialysis (BMED) for acid and base recovery and batch reverse osmosis (BRO) for water recovery are analyzed technically and economically as a dairy wastewater treatment solution. The proposed process layouts also aimed to utilize recovered water and chemical within same industrial plant. The hybridization of BMED with BRO process is used to reduce capital and operating cost of BMED unit and compared with the standalone BMED process. The analysis reveals that the hybridization of BRO-BMED system achieve 25.8% less unit cost and three times higher concentration of acid and base chemicals compare to standalone system. The comparison of system is done at optimum current density of BMED process and permeate flux of BRO process. Sensitivity analysis of permeate flux, current density and feed salinity is carried out. The higher feed concentration is desirable and reduces the cost in BMED process and same with current density but up to 409 and 255 A/m2 in hybrid and standalone system respectively. In hybrid system, the multi-response surface analysis observes that higher permeate flux in BRO reduces the BMED cost but increases the BRO cost and the minimum cost of 14 USD/kmol is achieved at 26 LMH permeate flux.

Simultaneous Separation and Recovery of Phosphorus from Aqueous Solution by Bipolar Membrane Electrodialysis

Recycling phosphorus from phosphorus-containing wastes and byproducts is a promising secondary phosphorus resource. Steelmaking slag is generated in large quantities as a byproduct of the iron and steelmaking industry, and contains phosphorus that could be a possible secondary phosphorus resource. Phosphorus can be extracted from slag into aqueous solution; however, the phosphorus concentration is generally lower than other elements, causing a problem for phosphorus recovery. In this study, bipolar membrane electrodialysis was applied to separate and recover phosphorus from solution. The reaction and performance of phosphorus recovery were investigated. The effect of initial phosphorus concentration, volume ratio, and electric potential on recovery process was determined. Ion adsorption on an anion-exchange membrane during the initial stages and ion competition between H2PO4- and OH- in the later stages are the main factors affecting the extraction efficiency. In this study, the maximum concentration ratio achieved was 2.46, and the minimum phosphorus concentration in treated solution was 3.64 mg/L, which is under the Japanese effluent standard. In general, bipolar membrane electrodialysis has good potential for concentrating and recovering phosphorus from aqueous solution.

Removal of heat stable salts from degraded amine solvent by “BMED+ED” two-stage electrodialysis unit

Due to the degradation reaction and the presence of acidic impurities (HCl, SO2, etc.) in the flue gas, heat stable salts (HSS) are widely present in the aqueous amine solvent for post-combustion CO2 capture. Accumulation of HSS in the solvent can lead to decreased absorption capacity and even corrosion of equipment in post-combustion capture (PCC) pilot plants. This study presents a novel “BMED+ED” two-stage electrodialysis unit for the efficient removal of HSS, including glycolate, formate, Cl−, and SO42−, from degraded amine solvent with an initial loading of approximately 0.38 mol/mol taken from the solvent loop of a PCC pilot plant after over 1000 hours of operation at real conditions. Experimental results showed that 94.93% of HSSs were removed with an initial HSS concentration of approximately 1920 ppm. The amine loss rate in the two-stage electrodialysis unit was much lower than that in a conventional ED unit, as protonated amine is further converted to organic amines by bipolar membrane electrodialysis. The energy consumption of the two-stage electrodialysis unit was 0.1643 kWh/L amine solvent, and the total cost for amine reclaiming was 1.8145 $/kg amine. This method effectively addressed the challenges of high amine loss rate in the traditional ED treatment process and hazardous wastewater disposal.