Researchers have developed a new biochar-based material that could significantly improve PFOS removal by both capturing the persistent contaminant from water and breaking it down using ultraviolet light.
The technology addresses one of the biggest challenges in treating per- and polyfluoroalkyl substances (PFAS), which are notoriously resistant to conventional treatment methods.
The study, published in the journal Biochar, was led by researchers from Jinan University and San Diego State University.
Their newly engineered material, known as Ga₂O₃@biochar, combines adsorption with photocatalytic degradation, enabling it to concentrate perfluorooctane sulfonate (PFOS) on its surface before destroying much of the pollutant through light-driven chemical reactions.
Laboratory testing demonstrated impressive results, with the material removing more than 99% of PFOS from water within 30 minutes.
Following ultraviolet exposure, over 80% of the captured PFOS was degraded, while more than 70% of its carbon-fluorine bonds were broken, highlighting its potential as a more sustainable approach to PFOS removal.
A new strategy for tackling PFAS pollution
PFOS is among the most persistent members of the PFAS family, often referred to as “forever chemicals” because of their exceptional chemical stability.
These compounds have been detected in groundwater, rivers and drinking water supplies worldwide, where they present a long-term environmental challenge.
Many existing treatment methods can extract PFOS from contaminated water, but they simply transfer the pollutant into another waste stream that still requires disposal or further treatment.
The newly developed Ga₂O₃@biochar material aims to overcome this limitation by integrating pollutant capture with chemical destruction in a single process.
The research team created the composite by embedding β-Ga₂O₃, a durable semiconductor photocatalyst, into porous biochar produced from wheat straw.
This combination provides a large surface area for adsorption while enabling ultraviolet light to initiate reactions that break down the concentrated PFOS molecules.
Engineered structure improves PFOS removal
Researchers evaluated several material compositions and found that biochar containing 1% gallium delivered the strongest overall performance.
The addition of β-Ga₂O₃ modified both the pore structure and electronic characteristics of the biochar. The composite exhibited greater mesoporosity, enhanced light absorption, a narrower electronic bandgap and more efficient separation of charge carriers generated during photocatalysis.
These structural improvements translated directly into higher treatment efficiency. Under test conditions, the material rapidly adsorbed PFOS before ultraviolet irradiation triggered extensive degradation of the pollutant.
Computational modelling using density functional theory also helped explain the enhanced performance. The simulations showed efficient electron transfer between the biochar and β-Ga₂O₃, reducing charge recombination and strengthening photocatalytic activity.
Laboratory experiments identified photogenerated electrons, superoxide radicals and singlet oxygen as the primary reactive species responsible for breaking down PFOS.
Regenerating the material during treatment
The study found that PFOS degradation followed a gradual chain-shortening process. Initial desulfonation reactions were followed by decarboxylation and progressive defluorination, steadily dismantling the highly stable molecular structure.
An additional advantage of the process is that photocatalytic degradation simultaneously regenerates the adsorbent.
Rather than relying on chemical regeneration methods that generate secondary waste, the material can be reused across multiple treatment cycles after ultraviolet exposure.
Potential for real-world water treatment
The researchers also evaluated the material using real groundwater samples. While treatment efficiency remained promising, naturally occurring compounds in environmental water influenced overall performance, indicating that site-specific water chemistry will require further investigation.
Future research will focus on assessing degradation byproducts, evaluating economic and environmental performance at larger scales, and adapting the technology to treat a broader range of PFAS compounds.
If successfully developed for commercial applications, the combined adsorption and degradation approach could represent an important step beyond conventional separation technologies, offering a more complete solution for PFOS removal while reducing the environmental burden associated with managing concentrated PFAS waste.
