membranes – Frontis Energy

DOI: 10.13140/RG.2.2.30211.46883

In a world increasingly defined by the need for cleaner processes, sustainable production, and advanced materials, membrane technology has emerged as a key enabler across multiple industries from water purification and energy generation to chemical separation and bioprocessing. Its high selectivity, compact footprint, and low energy requirements make it indispensable in meeting both environmental and performance demands.

At the heart of membrane fabrication lies a well-established method known as non-solvent-induced phase separation. This technique involves casting a polymer solution into a thin layer and exposing it to a non-solvent, typically through immersion or vapor contact, which triggers phase separation, forming a porous matrix with fine-tuned filtration properties. Due to its simplicity and scalability, this method has become a mainstay in industrial membrane production, offering reliable performance across many applications.

However, as industries demand more specialized and high-efficiency membranes, researchers are continuously pushing the boundaries of conventional fabrication techniques. One of the most promising advancements is the spray-modified non-solvent-induced phase separation method, which swaps immersion for targeted non-solvent spraying. This subtle yet powerful modification enables patterned surface architectures, improved permeability, and reduced fouling, all while maintaining the advantages of scalable continuous production. Such innovation is instrumental in tailoring membranes to meet the complex needs of modern filtration systems.

Building on this progress, a recent study conducted by the Catholic University Leuven in Belgium successfully adapted the spray-modified non-solvent-induced phase separation technique to a roll-to-roll, 12-inch pilot-scale platform. This represents a meaningful advancement from laboratory concept to industrial feasibility. The findings were recently published in the Membranes. Through strategic variations in polymer concentration, molecular weight, and the inclusion of hydrophilic additives such as polyethylene glycol and polyvinylpyrrolidone, researchers fabricated defect-free, uniformly patterned polysulfone ultrafiltration membranes with remarkable performance gains. Notably, these membranes delivered up to 350% higher water flux compared to traditional flat membranes, attributed to their deep surface patterns—reaching 825 µm—and a porous, finger-like internal structure that enhances throughput without sacrificing rejection efficiency.

Among the additives tested, polyethylene glycol emerged as the standout, yielding membranes with high pure water permeance (over 1000 Liters/m²/hour/bar) and consistent protein rejection levels (around 90%). These membranes also demonstrated excellent structural fidelity and homogeneity, which are critical for ensuring long-term durability and process reliability. The study further identified operational parameters, such as optimal casting speed, non-solvent spray rate, and solution viscosity control, as essential contributors to reproducible membrane quality and process scalability.

This leap from bench to pilot scale carries profound industrial implications. The ability to continuously produce high-flux, anti-fouling membranes with precise structural characteristics offers industries a robust and scalable filtration solution. Applications span from municipal and industrial wastewater treatment to biopharmaceutical production and food processing—sectors where membrane performance can directly influence both environmental outcomes and operational costs.

In essence, the optimized spray-modified non-solvent-induced phase separation approach does more than enhance membrane metrics; it embodies the transition from research novelty to commercial readiness. By bridging the gap between design and deployment, this work lays a foundational blueprint for mass-producing advanced membranes that are not only efficient, but also economically and environmentally viable. It is a compelling example of how thoughtful engineering and process innovation can move technologies from promising prototypes to real-world solutions, thus shaping the future of filtration in a world that urgently needs it.

Frontis Energy envisions a world transformed by sustainable membrane innovations, where clean water, resource efficiency, and resilient infrastructure are accessible to all.

Ilyas, et al., 2025, Pilot-scale polysulfone ultrafiltrationpPatterned membranes: phase-inversion parametric optimization on a roll-to-roll casting system, Membranes 15, 8, 228, DOI: 10.3390/membranes15080228

Image: Pixabay

DOI: 10.13140/RG.2.2.11561.25447

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.

Mankertz, Theis, Linnartz, Wessling, 2025, Membrane arrangement influences time to steady state in FCDI with multi-ionic salt solutions, Desalination, Volume 613, 118939, DOI: 10.1016/j.desal.2025.118939.

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Tag: membranes

Transforming water systems with scalable membrane solutions

Improved membrane configurations for capacitive flow-electrode desalination