Perfluorinated substances, or PFAS, often called forever chemicals, are pollutants that persist in the environment and resist natural breakdown. Recent research shows that ultrasound can help eliminate these compounds from groundwater, offering a potential method to reduce their presence in water supplies.
PFAS and related substances have been used for nearly a century in a wide range of consumer goods, from cookware and waterproof clothing to personal care products. Health researchers warn that exposure to PFAS is linked to various health issues, including birth defects and cancer. The chemical bonds that give PFAS their durability are tough to break, which makes removal from the environment particularly challenging.
Researchers at Ohio State University in the United States examined ultrasonic degradation, a process that uses sound to break apart molecules by targeting the bonds within PFAS. The study investigates the effectiveness of this technique against different PFAS structures and concentrations. The findings were published in the Journal of Physical Chemistry A (Citation: ACS Publications).
Groundwater often stores PFAS and related contaminants, making their removal a critical concern for public health and environmental protection. In their laboratory experiments, researchers created mixtures containing three sizes of fluorotelomer sulfonate compounds, representative PFAS found in firefighting foams. Over a three-hour testing period, smaller PFAS molecules degraded much more rapidly than larger ones, a contrast to several other treatment methods where small PFASs are harder to treat.
Co-author Linda Weavers, a professor of civil, environmental and geodetic engineering at Ohio State University, noted that the ability to process smaller PFAS more effectively underscores the potential value of ultrasonic treatment. This observation suggests a future where ultrasound-based methods could complement existing remediation technologies and broaden the toolkit for groundwater cleanup.
System versatility beyond PFAS cleanup
This work is part of a broader line of studies exploring how ultrasound can remove toxic PFAS compounds from the environment. Building on earlier efforts by Weavers, the same technology shows promise for degrading pharmaceuticals in drinking water and wastewater, offering a potential pathway to broader water purification applications (Citation: ACS Publications).
Weavers emphasizes that PFAS are distinctive because many conventional disposal methods fail to address them effectively. Consequently, researchers advocate for a diverse array of technologies to adapt to different PFAS compounds and varying environmental conditions.
Unlike methods that rely on oxidizing chemicals to break down contaminants, ultrasound treats PFAS by emitting low-frequency sound waves. Weavers explains that the process extends beyond the frequencies typically used in medical imaging, tapping into a powerful mechanism that drives chemical transformation in the liquid phase.
This is how the system works
A low-frequency ultrasound pressure wave creates compression in the solution, forming vapor pockets called cavitation bubbles. When these bubbles collapse, they release energy and heat, driving chemical reactions that destabilize the carbon-fluorine bonds that characterize PFAS. In the process, PFAS compounds can break down into smaller, less problematic byproducts that are easier to manage. Although the method can be energy-intensive and costly, it remains a compelling option to explore alongside other treatment strategies for safeguarding groundwater used for drinking and other purposes (Citation: ACS Publications).
Because ultrasound can clear PFAS from solutions so effectively, scientists and government agencies should consider its role in shaping future purification technologies and in combination with other treatment systems. While the current study does not propose an immediate, large-scale rollout, it may lay the groundwork for small, high-energy water filtration devices intended for home use in the future.
Weavers notes that the overarching goal is to scale the approach and determine what it would take to implement it on a larger scale. PFAS are pervasive, so advancing knowledge about how these compounds can be degraded is essential for informed decision-making moving forward.
Reference work: https://pubs.acs.org/doi/10.1021/acs.jpca.3c03011
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