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

The Potential of Electrodialysis with Mediating Solution (EDM) for Eliminating Alkaline Scaling: Experimental Validation and Mechanistic Elucidation

Alkaline scaling in the cathode chambers of conventional electrodialysis (ED) stacks presents significant challenges when desalinating solutions containing divalent cations. This scaling, resulting from the combined effects of water electrolysis and the migration of divalent cations from the feedwater into the catholyte, further extends from the cathode chamber to the surfaces of both the cation exchange membrane (CEM) and the anion exchange membrane (AEM) in the adjacent dilute chamber. This study aims to mitigate alkaline scaling, without pretreatment or antiscalant dosing, by optimizing the ED stack design to restrict divalent cation transport toward the cathode. We evaluated three ED stack configurations, each forming the cathode chamber with a distinct ion transport control mechanism: (1) a monovalent selective cation exchange membrane (SCEM), (2) a bipolar membrane (BPM), and (3) a mediating solution chamber adjacent to the cathode chamber (EDM). Our results indicated that stacks employing the SCEM or BPM partially restricted divalent cation migration but remained vulnerable to scaling under higher feed salinities, due to weakened Donnan exclusion within the SCEM, and strong internal ion polarization at the BPM interface. In contrast, the EDM stack exhibited superior antiscaling performance by combining strong Donnan exclusion through an AEM with ionic buffering in the mediating solution chamber, effectively blocking cation transport and eliminating conditions conducive to scaling. Additionally, the EDM stack maintained low electrical resistance and high operational stability, making it a simple, efficient, and cost-effective solution for scaling mitigation in ED systems.

Enhanced Schemes for Brine Valorization via Electrodialysis with Bipolar Membranes Powered by Renewable Energy

Powering water treatment technologies with renewable energies by using the process buffering capacity as a way to indirectly store energy has been recently proposed as an effective strategy for the smart use of energy. With this respect, the production of chemicals from waste brines via electrodialysis with bipolar membranes (EDBM) can be particularly suitable due to its high energy intensity along with the extreme flexibility of the process. This study demonstrates, through real-environment experiments at the pilot scale, the feasibility of coupling an EDBM pilot plant with renewable energies (solar). The pilot plant was tested in a continuous process configuration (feed and bleed mode) under two different irradiation scenarios, i.e., summer and winter. The use of the controllers implemented allowed us to maintain the target concentration for acid and base fixed at 0.5 mol L-1 in both scenarios. In the summer scenario, current efficiency (CE) values higher than 90% and specific energy consumption (SEC) values lower than 2 kWh kg-1 were obtained, still maintaining a specific productivity (SP) of about 0.2 kg h-1 m-2. In the winter scenario, a current efficiency >80% was obtained, while SEC and SP values up to 1.6 kWh kg-1 and 0.06 kg h-1 m-2 were found, respectively. Results suggest that EDBM technology is perfectly suitable for the valorization of waste brines by using green energy sources, thus paving the way for its development at an industrial scale.

A review of the potential of seawater brine for enhancing food security in hot arid climates: A case study of Qatar

This study explores Qatar's utilisation of seawater to support food security, emphasising the innovative strategies and technological advancements to address the environmental and agricultural challenges posed by rejected brine from desalination processes. It examines various brine treatment and disposal methodologies, highlighting the environmental impacts and proposing sustainable solutions to mitigate these effects. The discussion further explores the potential of electrodialysis and other emerging technologies for converting rejected brine into valuable agricultural resources, thereby contributing to food security in arid regions. Through a comprehensive review of current research and potential innovations, this study highlights the critical intersection of water resource management, environmental sustainability, and food production, particularly in Qatar's unique geographical and climatic conditions.

Exploring differential pressure-induced hydraulic flows in pilot-scale Electrodialysis with Bipolar Membranes

Electrodialysis with Bipolar Membranes (EDBM) is an electro-membrane process that produces acid and base from saline solutions using electricity. In previous research, this technology has predominantly been explored at the laboratory scale, with very few examples at the pilot scale. This study investigated, for the first time, how differential pressures applied between the EDBM channels affect its performance, utilizing a semi-industrial scale pilot - the largest ever studied in the literature. For this, inlet pressures from 0.5 to 1.5 barg were applied in the EDBM channels. Results were compared in terms of volume variation, product purities and key performance indicators, such as Current Efficiency (CE) and Specific Energy Consumption (SEC). Results indicate that changing the pressure between the channels induces a volumetric flow between compartments, which impacts the EDBM's performance. Specifically, the SEC ranged from 1.20 to 1.58 kWh kgNaOH-1, considering the energy required for both electricity and pumping at base concentration of ∼0.66 mol L-1. Notably, SEC values were 24% lower than the reference case study when operating with the identified best set of pressures. Under similar conditions, the CE varied between 64 % and 86 %, depending on the pressure applied between the channels. Moreover, using this set of pressures, acid and base product purities remained above 90%. This study advances pilot-scale EDBM process intensification, highlighting its potential for reduced energy consumption, increased sustainability, and industrial competitiveness.

Bound Water Enhances the Ion Selectivity of Highly Charged Polymer Membranes

Electrochemical technologies for water treatment, resource recovery, energy generation, and energy storage rely on charged polymer membranes to selectively transport ions. With the rise of applications involving hypersaline brines, such as management of desalination brine or the recovery of ions from brines, there is an urgent need for membranes that can sustain high conductivity and selectivity under such challenging conditions. Current membranes are constrained by an inherent trade-off between conductivity and selectivity, alongside concerns regarding their high costs. Moreover, a gap in the fundamental understanding of ion transport within charged membranes at high salinities prevents the development of membranes that could meet these stringent requirements efficiently. Here, we present the synthesis of scalable, highly charged membranes that demonstrate high conductivity and selectivity while contacting 1 and 5 molal NaCl solutions. A detailed analysis of the membrane transport properties reveals that the high proportion of bound water in the membranes, enabled by the high charge content and hydrophilic structure of the polymers, enhances both the ion partitioning and diffusion selectivities of the membranes. These structure/property relationships derived from this study offer valuable guidance for designing next-generation membranes that simultaneously achieve exceptional conductivity and selectivity in high-salinity conditions.

Technical and financial feasibility of a chemicals recovery and energy and water production from a dairy wastewater treatment plant

Due to the high volume of wastewater produced from dairy factories, it is necessary to integrate a water recovery process with the treatment plant. Today, bipolar membrane electrodialysis units (BMEUs) are increasingly developed for wastewater treatment and reutilizing. This article aims to develop and evaluate (technical and cost analyses) a combined BMEU/batch reverse osmosis unit (BROU) process for the recovery of chemicals and water from the dairy wastewater plant. The combined BROU/BMEU process is able to simultaneously produce water and strong base-acid, and reduce power consumption due to the injection of concentrated feed flow into the BMEU. A comprehensive comparative analysis on the performances of two combined and stand-alone BMEU configurations are developed. The proposed combined technology for dairy factory wastewater treatment is designed on a new structure and configuration that can address superior cost analysis compared to similar technologies. Further, the optimal values of permeate flux and current density as two vital and influencing parameters on the performance of the studied dairy wastewater treatment process were calculated and discussed. From the outcomes, the total cost of production in the combined configuration has been reduced by approximately 26% compared to the stand-alone configuration. Increasing the feed concentration rate using the batch reverse osmosis process for the dairy wastewater treatment process can be an ideal solution from an economic point of view. Moreover, point (current density, feed concentration rate, total unit cost) = 328.9 , 7 , 14.37 can be considered as an optimal point for the economic performance of the studied wastewater treatment process.

Reclaimed seawater discharge - Desalination brine treatment and resource recovery system

With the proliferation of reverse osmosis technology, seawater reverse osmosis desalination has been heralded as the solution to water scarcity for coastal regions. However, the large volume of desalination brine produced may pose an adverse environmental impact when directly discharged into the sea and result in energy wastage as the seawater pumped out is dumped back into the sea. Recently, zero liquid discharge has been extensively studied as a way to eliminate the aquatic ecotoxicity impact completely, despite being expensive and having a high carbon footprint. In this work, we propose a new strategy towards the treatment of brine to seawater level for disposal, dubbed reclaimed seawater discharge (RSD). This process is coupled with existing resource recovery techniques and waste alkali CO2 capture processes to produce an economically viable waste treatment process with minimal CO2 emissions. In this work, we placed significant focus on the electrolysis of brine, which simultaneously lowers the salinity of the desalination brine (56.0 ± 2.1 g/L) to seawater level (32.0 ± 1.4 g/L), generates alkali brine from seawater (pH 13.6) to remove impurities in brine (Mg2+ and Ca2+ to below ppm level), and recovers magnesium hydroxide, calcium carbonate, chlorine, bromine, and hydrogen gas as valuable resources. The RSD is further chemically dechlorinated and neutralised to pH 7.3 to be safe to discharge into the sea. The excess alkali brine is used to capture additional CO2 in the form of bicarbonates, achieving net abatement in climate change impact (9.90 CO2 e/m3) after product carbon abatements are accounted.

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.

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.