Per- and polyfluoroalkyl substances (PFAS) pose a major challenge to water pollution due to their persistence and resistance to conventional treatment methods. To address this issue, researchers around the world are turning to innovative technologies, particularly using bacteria or nanomaterials, to effectively remove PFAS from water.

What exactly are nanomaterials?

Nanomaterials are materials with dimensions on the nanometric scale, which is one billionth of a meter. To give you an idea:

• A water molecule measures about 1.5 nanometers (nm).
• A bacterium is about 1,000 nm long.
• A hair measures approximately 100,000 nm in diameter.

Nanomaterials began to gain significant interest in the 1980s, but their history dates back much further. The concept of manipulation on a nanometric scale was first introduced in 1959 by physicist Richard Feynman in his famous lecture, “There’s Plenty of Room at the Bottom.” He envisioned the possibility of manipulating atoms individually.

The first concrete developments of nanomaterials occurred in the 1970s and 1980s with the discovery of fullerenes (a nanometric form of carbon) by Harold Kroto, Robert Curl, and Richard Smalley in 1985, which earned them the Nobel Prize in Chemistry in 1996. The development of carbon nanotubes in the early 1990s by Sumio Iijima also marked a major breakthrough in the field.

Since then, nanomaterials have been extensively studied for their unique properties, paving the way for innovative applications in fields as diverse as medicine, electronics, energy, textiles, and cosmetics. Their large specific surface area and increased chemical reactivity make them particularly interesting for environmental applications, including water purification.

Why use nanomaterials to fight PFAS?

Nanomaterials can interact with PFAS in water in various ways, depending on their composition and structure. The main approaches under study include:

1. Adsorption: Some nanomaterials, such as carbon nanotubes and modified graphene, can “adsorb” PFAS due to their large specific surface area. Adsorption means that PFAS molecules attach to the surface of the nanomaterial, allowing for their removal from water.
2. Catalytic degradation: Some nanoparticles can help break the carbon-fluorine chains in PFAS, triggering the degradation of PFAS into less persistent and/or less harmful byproducts.
3. Advanced filtration: The size of nanomaterials opens the possibility of creating membranes with pores so small that they could filter out all contaminants from water.

Promising ongoing studies

Several recent studies show promising results regarding the use of nanomaterials to remove PFAS from water. Here are some of the most notable research efforts:

1. Adsorption:
   • A study conducted by the State University of New York demonstrated that zero-valent iron nanoparticles (nZVI) can effectively reduce PFAS concentrations in water. The nZVI degrades PFAS through redox reactions, transforming these compounds into less toxic products. Their experiments reported an 85% reduction of PFOS after just 10 minutes of exposure to zero-valent iron nanoparticles.
   • A team from the University of El Paso, Texas, studied the use of modified carbon nanotubes for PFAS adsorption. Preliminary results indicate rapid and efficient adsorption of PFAS, even at low concentrations: carbon nanotubes managed to remove 100% of PFOA in the water sample in just 3.5 hours. The nanotubes can then be regenerated and reused, making them a potentially sustainable option for water treatment.
2. Degradation:
   • South Korean researchers recently explored the use of MMO-TiO2 nanoparticles to catalyze the degradation of PFAS under UV light. This method, known as photodegradation, could offer a solution for contaminated sites exposed to sunlight. Their initial results promise more than 95% elimination of PFOA subjected to this treatment.
3. Nanostructured membranes:
   • Nanofiber-based membranes have already been on the market for a few years. Some filters equipped with these membranes can filter up to 99% of PFAS present in water. These membranes are designed to be durable and resistant to clogging, a common issue in conventional filtration technologies.

Challenges and future outlook

Although the results are encouraging, several challenges remain before these technologies can be applied on a large scale. One of the main obstacles is the production cost of nanomaterials, which remains high. Moreover, the safety of the nanomaterials themselves must be assessed, as some nanoparticles can pose risks to human health and the environment if not properly managed.

Despite these challenges, research into nanomaterials for PFAS removal is advancing, with numerous initiatives aimed at reducing costs and improving process efficiency. As these technologies progress, they could offer a viable solution for treating PFAS-contaminated water, thus protecting ecosystems and public health.

If you want to stay informed on this crucial topic, be sure to regularly visit our blog at infopfas.com and follow our updates on social media!

Sources :

• There’s Plenty of Room at the Bottom, Wikipedia
• Richard E. Smalley, Robert F. Curl, and Harold W. Kroto, Science History Institute
• The Discovery and Future of Carbon Nanotubes Sumio Iijima, NEC
• Redox-active rGO-nZVI nanohybrid-catalyzed chain shortening of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), Science Direct
• Enhanced adsorption of PFOA with nano MgAl₂O₄@CNTs: influence of pH and dosage, and environmental conditions, Science Direct
• Enhanced removal of perfluoroalkyl substances using MMO-TiO₂ visible light photocatalyst, Science Direct
• Efficient removal of per- and polyfluoroalkyl substances (PFASs) in drinking water treatment: nanofiltration combined with active carbon or anion exchange, Royal Society of Chemistry

*Images by Starline and DC Studio, from Freepik