Purification method removes PFAS from water while transforming waste into high-value graphene

Rice University researchers have developed an innovative solution to a pressing environmental challenge: removing and destroying per- and polyfluoroalkyl substances (PFAS), commonly called “forever chemicals.”

A study led by James Tour, the T.T. and W.F. Chao Professor of Chemistry and professor of materials science and nanoengineering, and graduate student Phelecia Scotland unveils a method that not only eliminates PFAS from water systems but also transforms waste into high-value graphene, offering a cost-effective and sustainable approach to environmental remediation. This research was published March 31 in Nature Water.

PFAS are synthetic compounds in various consumer products, valued for their heat, water and oil resistance. However, their chemical stability has made them persistent in the environment, contaminating water supplies and posing significant health risks, including cancer and immune system disruptions. Traditional methods of PFAS disposal are costly, energy-intensive and often generate secondary pollutants, prompting the need for innovative solutions that are more efficient and environmentally friendly.

“Our method doesn’t just destroy these hazardous chemicals; it turns waste into something of value,” Tour said. “By upcycling the spent carbon into graphene, we’ve created a process that’s not only environmentally beneficial but also economically viable, helping to offset the costs of remediation.”

The research team’s process employs flash joule heating (FJH) to tackle these challenges. By combining granular activated carbon (GAC) saturated with PFAS and mineralizing agents like sodium or calcium salts, the researchers applied a high voltage to generate temperatures exceeding 3,000 degrees Celsius in under one second.

The intense heat breaks down the strong carbon-fluorine bonds in PFAS, converting them into inert, nontoxic fluoride salts. Simultaneously, the GAC is upcycled into graphene, a valuable material used in industries ranging from electronics to construction.

The research results yielded more than 96% defluorination efficiency and 99.98% removal of perfluorooctanoic acid (PFOA), one of the most common PFAS pollutants. Analytical tests confirmed that the reaction produced undetectable amounts of harmful volatile organic fluorides, a common byproduct of other PFAS treatments. The method also eliminates the secondary waste associated with traditional disposal methods such as incineration or adding spent carbon to landfills.

“This dual-purpose approach is a game changer,” Scotland said. “It transforms waste into a resource while providing a scalable, cost-effective solution to an urgent environmental issue.”

The implications of this research extend beyond PFOA and perfluorooctane sulfonic acid, the two most studied PFAS; it even works on the most recalcitrant PFAS type, Teflon R. The high temperatures achieved during FJH suggest that this method could degrade a wide range of PFAS compounds, paving the way for broader water treatment and waste management applications. The FJH process can also be tailored to produce other valuable carbon-based materials, including carbon nanotubes and nanodiamonds, further enhancing its versatility and economic appeal.

“With its promise of zero net cost, scalability and environmental benefits, our method represents a step forward in the fight against forever chemicals,” Scotland said. “As concerns over PFAS contamination continue to grow, this breakthrough offers hope for safeguarding water quality and protecting public health worldwide.”