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Advances in Ammonium Recovery with Bioelectrical Systems

DOI: 10.13140/RG.2.2.16014.22082

In recent decades, the focus of wastewater treatment has shifted from mere disposal to the recovery of valuable resources. This approach aims to harness energy and nutrients found in wastewater. Among emerging technologies are bioelectrical systems, which can recover not only energy and carbon but also valuable compounds like ammonium. Nitrogen bound in ammonium is a key component of fertilizers. Today, two-thirds of this resource are produced through the highly energy-intensive Haber-Bosch process using natural gas extracted from air. Fertilizer production significantly contributes to anthropogenic CO₂ emissions and, ultimately, to global warming.

Bioelectrical systems for ammonium recovery are classified into microbial fuel cells and microbial electrolysis cells. In both, electrogenic microorganisms oxidize organic matter in wastewater into carbon dioxide and protons. Exoelectrogens, also known as anode-respiring bacteria, use the anode as an electron acceptor instead of oxygen, thereby gaining energy for their metabolic processes.

By combining microbial activity with electrochemical processes, chemical reactions in wastewater treatment are catalyzed efficiently. This novel biocatalytic application still faces challenges in terms of optimization for practical use. At Frontis Energy, we have already demonstrated through a patented process that ammonium can be effectively removed from wastewater using bioelectrical systems. We are currently working on scaling this method for industrial deployment. However, a comprehensive understanding of the underlying processes and recovery mechanisms is still lacking.

A new study conducted by the Autonomous University of Barcelona investigated the development and optimization of bioelectrical systems aimed at recovering ammonium from wastewater in an energy-efficient and concentrated form. The findings were recently published in Bioelectrochemistry. Using a three-chamber configuration with a hydrophobic membrane, the researchers systematically examined the influence of different levels of electric current and ammonium concentrations on recovery efficiency. The system achieved its highest ammonium recovery rate of 55 g/m²/day at a current of 75 mA. Overall, a 97% removal of ammonium from a 0.3% solution was attained.

Notably, electrons flow from the anode to the cathode via an external circuit, where they react with an electron acceptor. In ammonium recovery systems, ammonium ions migrate from the anode to the cathode through a cation exchange membrane, driven by concentration gradients and the electric field, allowing them to accumulate in the cathode chamber.

While this ion transport mechanism supports efficient ammonium recovery, the researchers found that high-performance operation led to material wear at the cathode. This highlights the need to balance operational intensity with material durability. Consequently, the team explored different cathode materials and voltages. Stainless steel electrodes operated at 1.4 V yielded the best results, achieving a removal rate of 21 g/m²/day and a recovery rate of 17 g/m²/day, primarily due to enhanced cation migration resulting from higher current density.

Long-term experiments revealed that higher ammonium concentration in the anolyte significantly improves selective migration of ammonium ions through the cation exchange membrane, further boosting system performance. Operating at 1.4 V increased recovery efficiency and reduced energy consumption per gram of nitrogen—making the process more cost-effective and environmentally friendly.

These insights underscore the practical potential of bioelectrical systems as a pioneering solution for sustainable nitrogen recovery. By fine-tuning material selection, system design, and operational parameters, high ammonium removal and recovery rates can be achieved with minimal energy input.

From an industrial perspective, this study represents a scalable advance in resource recovery within existing wastewater treatment infrastructures. If scaled, the technology could reduce reliance on the energy-intensive Haber-Bosch process.

Since concentrated ammonium is a commercially viable product, its recovery reduces operational costs for wastewater treatment plants. If the scaled-up process maintains its long-term stability and low energy demand, these would be compelling arguments for adopting bioelectrical technologies as part of a circular economy.

At Frontis Energy, we see great potential in scaling this technology and making a meaningful contribution to sustainable wastewater treatment.

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Improved membrane configurations for capacitive flow-electrode desalination

DOI: 10.13140/RG.2.2.19476.16002

With the growing global scarcity of drinking water, the demand for practical and energy-efficient desalination methods is on the rise. Among potential solutions are osmotic desalination methods like capacitive deionization and its advanced form, flow-electrode capacitive deionization (FCDI). Flow electrodes are streaming electrodes composed of conductive particles suspended in a liquid. When electrically charged, these particles behave like capacitors and gain capacitive properties.

In flow-electrode deionization, flowable carbon electrodes are combined with ion-exchange membranes. The use of membranes enables continuous and efficient desalination. Membranes induce a selective transport of charged ions, allowing oppositely charged ions (counterions) to pass while repelling similarly charged ions (co-ions). This selective ion transport is essential for targeted salt removal from the feed stream.

Research advancements have improved membrane properties, associated ion selectivity, and the design of galvanic cells, leading to practical applications. For example, flow-electrode deionization was tested for industrial feasibility in a pilot plant in 2023. Performance optimization depends significantly on understanding how ion transport behaves with different membrane configurations. Ion-exchange membranes play a key role in controlling ion movement. Certain membrane arrangements, such as membrane “sandwiches” made of anion and cation exchange membranes, significantly accelerated desalination. While promising results were achieved with simple salt solutions like NaCl and KCl, mixtures of diverse ions, as found naturally in seawater, are more challenging.

Researchers from RWTH Aachen University recently investigated how different ion-exchange membrane arrangements affect selective ion removal from complex salt mixtures, such as those containing carbonate and sulfate ions, in flow-electrode deionization. Their findings were published in the journal Desalination. Two deionization modules with different membrane setups were analyzed. Membrane layers were tested with the cation membrane on the inside and the anion membrane on the outside, and vice versa. Both configurations delivered similar desalination performance, but the time to reach a stable state varied depending on the arrangement and the flow electrode’s buffering capacity.

The tested anion exchange membranes showed a higher affinity for sulfate ions than for carbonate ions, which delayed stabilization in some cases. Strategies like reducing electrode volume and steering specific ions along the electrode path helped reach the steady state more quickly. These findings underscore the importance of membrane selectivity, electrode properties, and system design in enhancing the performance of flow-electrode deionization, especially for mixed-ion water sources.

The effectiveness of the process depends not just on reaching a steady desalination state but also on managing ion selectivity and system adaptation. With saltwater containing multiple cations and anions, membrane arrangement alone is not enough to achieve the desired results. To tackle these challenges, strategies like membrane coatings or modifying electrode properties must be considered.

The researchers also addressed evaluation methods in their study. Interestingly, measuring conductivity alone is not sufficient to assess desalination performance. While it indicates total salt concentration, it does not reflect changes in salt composition. Therefore, more precise evaluation methods are needed to meet specific requirements.

These advances are crucial for optimizing flow-electrode deionization performance and meeting the growing demand for efficient, adaptable water treatment technologies. At Frontis Energy, we are excited to see how this groundbreaking technology will scale in the future.

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Electrolytic water splitting for binders in building material

DOI: 10.13140/RG.2.2.27780.18562

The oceans are rich in magnesium resources, which that could be used in the production of construction materials. Sorel cement (magnesium cement), for example, can be used in interior building applications as an alternative to screed. Extracting magnesium from seawater traditionally requires a highly energy-intensive calcination process to isolate magnesium oxide (magnesia). The innovative method of electrolysis-controlled water splitting can bypass this process, significantly reducing CO₂ emissions.

To obtain the precursor of magnesia, magnesium hydroxide (Mg[OH]₂), an alkaline solution must be produced. While previous research has investigated electrochemical methods for hydroxide production, few studies have combined efficient alkali synthesis with the direct precipitation of magnesium hydroxide to make magnesia for low-carbon cement. This critical knowledge gap in optimizing energy and material efficiency has now been addressed.

A new study led by a research team at Columbia University used electrochemical water splitting at low voltages (1.6–2.0 V). Hydroxide ions (OH⁻) were generated from seawater through hydrogen production. This led to the direct precipitation of magnesium hydroxide. The findings were recently published in the journal Desalination. This new approach reduces energy intensity by 52–78%. Normally, the energy consumption per ton of MgO is 0.56 MWh. With the new method, carbon emissions per ton of magnesia can be reduced by up to 0.41 tons of CO₂.

To further improve production efficiency, the nanostructure of magnesium hydroxide was optimized using urea as a crosslinker. This enhanced its reactivity, porosity, and specific surface area. At an optimal urea concentration of 0.2 mol/L, magnesia particles exhibited excellent binding properties. The researchers attributed this to the sealing effects of rosette-shaped dypingite and rod-shaped nesquehonite. According to the authors, the formation of these minerals facilitates CO₂ incorporation and enhances carbonate hardening.

Advances in symmetric electrochemical systems, as demonstrated in this study, result in up to a 78% reduction in energy demand for the production of alkaline solutions. This gives these methods the potential to serve as viable alternatives to traditional processes. The further optimization of electrodes and electrolytes represents a pioneering approach to the carbon-neutral production of building materials and alkalis. Additionally, this method highlights how construction material manufacturing can efficiently lead to large-scale CO₂ mineralization. As a result, the greenhouse gas can be permanently removed from the atmosphere.

The industrial scaling of electrochemical alkali production can reduce operating costs, minimize environmental impact, and improve the properties of low-carbon building materials. The economic aspects of this manufacturing process are particularly noteworthy, as the demand for efficient binding materials continues to grow.

At Frontis Energy, we are committed to promoting sustainable and economically viable energy solutions. Research like this provides valuable insights and innovations to support such sustainable advancements.

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From waste heat to ultrapure water: A new technology transforming renewable hydrogen

Hydrogen (H₂), produced using renewable energy, has emerged as a possible alternative to fossil fuel. This versatile molecule can serve as an energy carrier, an efficient storage solution, and a sustainable feedstock for transportation, chemical processing, and energy systems worldwide.

Unlike fossil fuels, hydrogen produces no harmful emissions when used. It can be generated using electrolyzers running on renewable energy and abundant water as feedstock. It then becomes a renewable and sustainable energy source, reducing reliance on depleting fossil fuel reserves, helping combat climate change. Consequently, hydrogen production has become a key priority on the political agenda of numerous countries.

However, the water used in electrolyzers must be ultrapure in order to protect the electrodes of electrolyzers from poisoning and avoid chloride oxidation to chlorine. Abundant seawater adds several challenges when directly fed to electrolyzer plants for hydrogen production, making highly pure water, specifically ultrapure water, an expensive necessity. Ultrapure water is produced in a series of steps, including pretreatment to remove suspended solids and desalination to eliminate salts, organics, and colloidal particles. Polishing techniques such as deionization, degasification, and ultraviolet treatment are then used to achieve the required quality. Among these processes, desalination is particularly critical for removing most impurities.

Reverse osmosis, especially seawater reverse osmosis, is a widely used desalination technology but has notable drawbacks, such as requiring high-pressure operation (high energy consumption), intensive pretreatment, and producing concentrated brine, which can harm marine ecosystems when discharged. Membrane distillation has gained attention as an alternative for producing high-quality water and supporting recovery applications. It operates at lower temperatures and has the ability to utilize waste heat.

Membrane distillation is a thermal separation process where a vapor pressure difference across a hydrophobic membrane causes liquid particles to phase change and pass through as gas. Operating at ambient pressure and utilizing low-temperature heat sources (<90 °C), membrane distillation offers significant advantages. However, research on membrane distillation as a viable alternative to reverse osmosis for ultrapure water production remains limited, particularly in areas such as module design and techno-economic analysis.

A group of researchers at the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Germany, has explored the potential of membrane distillation as a cost- and energy-efficient alternative to reverse osmosis for producing ultrapure water for proton exchange membrane (PEM) electrolyzers. The findings were recently published in the Desalination Journal. They introduced membrane distillation as a possible alternative to reverse osmosis for ultrapure water production. But here is the twist: the membrane distillation system ingeniously taps into waste heat from a 5 MW proton exchange membrane electrolyzer, transforming what would typically be an efficiency liability into an asset for sustainability. So far, their results are impressive—membrane distillation not only produces exceptional distillate (<3 μS/cm) but does so at a cost ranging from €2.33 to €2.85 per ton of distillate, compared to reverse osmosis’s €2.80 to €5.51. Using membrane distillation, seawater desalination could be 50% or more cheaper.

Economic analyses highlight that membrane distillation’s cost-effectiveness is driven by its low electrical energy requirements and optimized short-channel module design. Its impressive energy efficiency, enabled using low-grade thermal energy, establishes membrane distillation as a highly versatile and environmentally friendly solution that aligns seamlessly with the vision for renewable hydrogen production. This study positions membrane distillation as more than just an alternative to reverse osmosis: it is a smarter and greener approach to ultrapure water production.

Their findings have the potential to reshape the industrial approach to ultrapure water production. By demonstrating an efficient use of waste heat and providing a more economical solution, it offers industries a pathway to lower operational costs while advancing sustainability. This aligns particularly well with sectors striving for greener operations, such as renewable hydrogen production and other energy-intensive applications. Moreover, the adoption of membrane distillation could catalyze innovation in system design and integration, encouraging industries to optimize processes and reduce dependence on traditional, energy-intensive methods. This shift can contribute to broader sustainability goals and improve the economic feasibility of renewable energy initiatives.

At Frontis Energy, we are committed to advancing sustainable and green energy solutions by embracing innovative technologies like membrane distillation, bringing us closer to a sustainable future.

Schwantes et al. 2025 Thermally driven ultrapure water production for water electrolysis – A techno-economic analysis of membrane distillation, Volume 608, 118848, DOI: 10.1016/j.desal.2025.118848.

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Unlocking the Potential of Conducting Polymers for Sustainable Water Treatment and Energy Solutions

Carbon based materials have a broad range of applications such as energy storage and conversion, electronics, nanotechnology, water purification, and catalysis. They are made of an element which is available everywhere.

In recent times, the electrochemical features of carbon-based electrodes are being enhanced by using conducting polymers. Carbon cloth, woven from carbon microfibers, serves as a promising carbon-based electrode, which acts as a durable and cost-effective medium for facilitating electrochemical reactions that degrade pollutants and improve water quality. These electrodes, notable for their mechanical flexibility, strength, and cost-effectiveness, are employed in processes such as electrochemical oxidation, microbial fuel cells, and other advanced wastewater treatment technologies.

Due to a few limitations of pristine carbon cloth electrodes such as low specific capacitance and limited wettability associated with its inherent hydrophobicity, scientists conduct research to improve the modern electrodes. For instance, since wettability is crucial for for immersing the electrode surface in liquid and ensuring interaction with contaminants, enhancing it is always beneficial for the process. Improving the performance of carbon cloth electrodes could lead to more efficient treatment, faster reaction times, and better overall performance.

A research group at San Diego State University undertook the task of addressing these limitations by making conformal conducting polymer films on carbon fibers via oxidative chemical vapor deposition (oCVD) method. They recently published their results in the Advanced Material Interface Journal. With antimony pentachloride (SbCl5) as the oxidant, they developed a highly uniform coating of poly(3,4-ethylenedioxythiophene) (PEDOT) on three-dimensional porous fibers. The oCVD technique ensures uniform coatings while preserving the geometric and functional properties of the carbon cloth, making it a promising approach for enhancing electrochemical performance.

The PEDOT-coated carbon cloth electrodes achieved a remarkable improvement in specific capacitance and pseudocapacitance compared to pristine carbon cloth. Depending on the deposition temperature, the oCVD PEDOT-coated electrodes showed a 1.5- to 2.3-fold enhancement in specific capacitance. Notably, the electrode fabricated at a deposition temperature of 80 °C exhibited the highest specific capacitance and superior electrochemical performance. Adjusting the deposition temperature to optimize performance can help tailor carbon cloth electrodes for specific wastewater treatment needs.

The investigation underscores the effectiveness of the oCVD method in addressing the limitations of carbon cloth electrodes and expanding their potential applications in wastewater treatment and electrochemical energy storage devices. Furthermore, the researchers showed that PEDOT-coated carbon cloth can be applied as supercapacitors, where flexibility and high capacitance are critical. It should be noted that the study not only showcases significant advancements in material design but also open new avenues for optimizing electrode performance for diverse applications.

Overall, the findings emphasize the growing potential of advanced electrode technologies in addressing industrial challenges. By improving the functionality of carbon-based electrodes through novel material coatings, industries can achieve more efficient and tailored solutions for both wastewater treatment and energy storage. The ability to fine-tune electrode properties to meet specific requirements offers a pathway toward the development of highly efective and cost-efficient technologies, which could be a game-changer for sectors focused on sustainability and resource management. As these innovations continue to evolve, they have the potential to significantly improve operational efficiency and environmental impact across various industries. For example, in wastewater treatment, electrochemical processes such as electrocoagulation, electrooxidation, or electroreduction are often used to remove contaminants.

At Frontis Energy, we believe that improvements and customization can aid in designing electrodes tailored to specific contaminants or types of wastewater.

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