Tag: biofouling

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Transforming water systems with scalable membrane solutions

Fresh water from a faucet

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

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Water desalination and fluoride ions removal from water using electrodialysis

Clean freshwater is of the utmost importance for our health. Despite its central role for our lives, progressing global industrialization threatens freshwater resources around the world. Albeit a vital trace element, fluoride is a serious public health threat. Absorbed in larger quantities for a long time, fluoride causes fluorosis, a form permanent poising responsible for irreparable bone damage.

Fluoride bearing rocks are particularly common in India. Fluoride is leached into adjacent aquifers and contaminates the soil. Sometimes, the concentration of fluoride ions in Indian aquifers exceeds 30 mg/L. Toxic concentrations of 20-80 mg / day over a period of 10 to 20 years cause irreparable damage to the human body.

Fluoride ions in groundwater are removed for water treatment using membranes. However, such membranes foul easily, for example by bacteria present in wastewater or other deposits.  Fouling can become a serious threat to public health. Therefore, a particular focus in membrane research is on the development of fluoride removing membranes that prevent fouling. It can be accomplished when bacterial growth is slowed down or inhibited entirely. For water treatment, antimicrobial surface modifications are used in high-quality membranes for ultrafiltration, nanofiltration, reverse osmosis and electrodialysis.

Electrodialysis is often used to remove water contamination, because only little energy is needed for the process. For electrodialysis membranes, salt deposits are an economic risk that is to be avoided. Precipitates can occur when the concentration of bivalent ions in the water is too high. Added to precipitates comes the risk of biofouling caused by microbial growth. Both affect the performance of electrodialysis membranes, causing economic losses as the membranes must be cleaned or replaced. For efficient water treatment, it is therefore important to improve the thermal and mechanical properties of the membranes.

A group of scientists have synthesized a composite anion exchange membrane for water-salt altitude and fluoride ion removal by electrodialysis that has improved antimicrobial properties. She published her results in the journal ACS ES&T Water. The consortium consisted of researchers of the Academy of Scientific and Innovative Research in Ghaziabad, India and the University of Tokyo.

Their anion exchange membranes are based on cross-linked terpolymers with built-in silver nanoparticles to slow microbial growth. The membranes are suitable for water desalination and fluoride ion removal by electrodialysis. The preparation of the terpolymers and polyacrylonitrile copolymers was carried out by N-alkylation using various alkyl halides. N-alkylation of the terpolymer through various alkyl groups affected the water absorption, hydrophobicity, ion transport and ionic conductivity of the membrane. Long alkyl groups increased the effectiveness of fluoride removal as well as the oxidative and physical stability of the membranes. The suitability of the composite membranes was verified by testing removal efficiency of fluoride ions (5.5 and 11 mg/L) from a sodium chloride solution (2 g/L) by electrodialysis at an applied voltage of 2 V.

The incorporation of 0.03% silver nanoparticles in the quaternized polymer caused the desired antimicrobial effect. The uniform distribution of silver nanoparticles in the liquid and solid phases was detected by transmission electron microscopy and atomic force microscopy. The attachment of bacteria was quantified counting colony forming units and 100x lower when silver nanoparticles were present in the membrane. The reduced microbial attachment to the membrane surface is therefore due to the antimicrobial effect of the silver nanoparticles. The small amount of 0.03% silver nanoparticles was sufficient to achieve desired antimicrobial effect in the membrane.

After 15 days and at a water temperature of 50°C, no detectable silver leaching occurred. The novel membranes are thus an improved anion exchange solution with antimicrobial properties for efficient removal of fluorine and desalination by electrodialysis.

Methodology

The entire synthesis was carried out in four steps:

  • Step 1: Silver nitrate was diluted with deionized water to produce a 30 mm solution
  • Step 2: Terpolymer and quaternized terpolymers were prepared by free radical polymerization
  • Step 3: Composite additives were prepared by the reduction of silver nitrate with sodium borohydrite in the presence of dimethylformamide
  • Step 4: The membrane was networked with the silver nanoparticles

Characterization of the anion exchange membrane

The membrane was characterized using several analytical methods:

  • UV-VIS and IR spectroscopy
  • Incorporation of silver nanoparticles by scanning electron microscopy, atomic force microscopy and transmission electron microscopy
  • Thermal stability, tensile properties, solubility and further physicochemical and electrochemical properties of the silver nanoparticle composite
  • Desalination and fluoride removal
  • The effectiveness of silver nanoparticles on microbial attachment
  • Energy consumption and efficiency during water desalination and fluoride removal by the composite membrane
  • Membrane stability with respect to pH, temperature and Fenton’s Reagent was evaluated

Reference:

Pal et al. 2021 “Composite Anion Exchange Membranes with Antibacterial Properties for Desalination and Fluoride Ion Removal” ACS ES&T Water 1 (10), 2206-2216, https://doi.org/10.1021/acsestwater.1c00147

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Self-cleaning membranes for biofouling control and prevention in water treatment

Membrane-based water treatment is critical for obtaining potable water, for example through wastewater treatment and seawater desalination. However, membrane fouling remains a common undesirable phenomenon affecting all membrane-based separation processes. Various efforts have been made to either directly control biofouling or to prevent it.

Ceramic membranes have better thermal and chemical stability along with higher fouling resistance and longer lifetimes when compared to polymeric membranes. These properties render ceramic membranes superior to polymers.

During the filtration process, the amount of water that can pass through a membrane is known as membrane flux. Due to membrane fouling, this flux is reduced and the affected membrane needs to be refurbished. Different membrane cleaning strategies have been researched including self-cleaning conductive polymeric membrane and electrically-assisted filtration but neither of them has shown a satisfactory flux recovery behavior.

Previous researches have suggested the use of ‘nano zeolite’ and carbon nanostructures for water treatment and desalination applications.

  • Zeolites are crystalline aluminosilicates possessing a well-defined inorganic structure, whose microporous 3-D channels and pores act as filters.
  • Carbon nanostructures consist of highly entangled carbon nanotubes which are made through a standardized chemical vapor deposition method.

To investigate the use of ceramic membranes made from nano zeolite and carbon nanostructures, a group of researchers at the New York University Abu Dhabi, United Arab Emirates, developed a new electro-ceramic membrane and evaluated its antifouling performance. Their research findings were published in the Chemical Engineering Journal.

Research Approach:

Zeolite / CNS membrane preparation:

Nano zeolite-Y (nano-Y) membranes were prepared by dispersing the desired amounts of nano-Y, carbon nanostructures, and polyvinylidene fluoride (PVDF) binder in a water-alcohol solution.

The suspension was vacuum filtered through a microfiltration membrane filter and the membrane was peeled off from it before drying it at room temperature.

Three different ratios of zeolite and carbon nanostructures were prepared initially, with 60, 70, and 80 wt% zeolite. The carbon nanostructures and the binder were prepared at a ratio of 1:1.

Membrane characterization:

The electrical conductivity and mechanical properties of the dried membranes were investigated.

The surface morphology of the zeolite carbon nanostructure membrane was studied through scanning electron microscopy and transmission electron microscopy.

Other tests including the membrane contact angle test were also performed on the different labeled membranes.

Membrane cleaning setup and antibacterial assessment:

Two foulants, yeast (200 mg / L) and sodium alginate (30 mg / L) were used as biofoulants.

A custom-made cell was designed and a fresh membrane was used for each electrochemical measurement performed using linear sweep voltammetry.

Antibacterial properties of the nano-Y carbon nanostructure membranes were determined by the disk diffusion method. Different bacteria were cultured overnight at 37°C in a shaking incubator at 100 rpm.

Results:

Membrane cross-sections showed a uniform distribution of nano-zeolite particles with the carbon nanostructure. Decreasing tensile strength was seen interpreted as successful nano zeolite incorporation. These values changed from 3.3 MPa to 2.1, 1.1 or 0.3 MPa, respectively for 60, 70 and 80 weight% nano-Y. In addition, a decrease in water contact angle from 84.7±2° to 18±4° was demonstrated within 4 min.

The composite membrane demonstrated enhanced electrocatalytic activity for hydrogen evolution in two foulants; yeast and sodium alginate.
These MF electro-ceramic self-cleaning, anti-bacterial membranes seem promising for various separation processes such as in wastewater treatment, dye separation and oil / water separation where fouling and bacterial growth are a major concern.

(Photo: WET GmbH, Attribution, via Wikimedia Commons)

Reference: https://doi.org/10.1016/j.cej.2020.128395 Electro-ceramic self-cleaning membranes for biofouling control and prevention in water treatment, Chemical Engineering Journal, Volume 415, 2021