New Catalyst System Promises More Efficient and Sustainable Reduction of PFAS ‘Forever Chemicals’

A type of compound called per-and poly-fluoroalkyl substances (PFAS) is known as "forever chemicals" because of its high resistance against degradation. Despite efforts to degrade PFAS, current methods are limited by a lack of scalable, efficient, and environmentally friendly processes.

Existing Methods of Reducing PFAS

PFAS is a fluorinated compound bound by strong carbon-fluoride (C-F) bonds, which are difficult to break. It is this stable chemical structure that leads to thousands of variants of PFAS, such as clothing, cosmetics, non-stick cookware, and food packaging.

The current process used to remove PFAS from water and soil involves the absorption of this compound into carbon material. Using a pad of activated carbon and a stream of flowing water, PFAS can be absorbed, but the activated carbon-carbon needs to be burnt in order to destroy or safely store PFAS.

This method is laborious and energy inefficient, in addition to the environmental effects of burning carbon material. There are physical separation techniques that offer solutions for isolating PFAS, but they do not actually destroy the chemical. Instead, they only exacerbate the management challenges associated with waste contamination.

Scientists also explore the technique of using a strong oxidizing agent to break PFAS apart. However, this approach requires aggressive substances that break PFAS down into smaller pieces, which may even be harder to completely remove.

Effective Catalyst Treatment

For decades, a type of eco-friendly chemical reducing agent called nano zero-valent metals (nZVMs) have been extensively used in treating groundwater and soil contaminated with chlorinated compounds. Despite its potential, there has been a lack of research into the use of nZVMZ in defluorinating PFAS, largely because of the lack of proper catalyst needed to activate the reaction.

Prior studies suggest that PFAS can be degraded using nano zero-valent zinc and vitamin B12, a naturally occurring water soluble catalyst which is present in our daily diet. Still, the process was found to be slow and inefficient.

Since B12 has the potential to catalyze this reaction, a team of researchers from the University of New South Wales (UNSW) wanted to synthesize a catalyst that mirrors the unique ring shape of B12. Led by Dr. Jun Sun and Professor Naresh Kumar, they developed a new method for efficient and sustainable PFAS remediation.

The synthesis was carried out using a structure called a porphyrin ring. It was tested on two common types of PFAS: branched PFOS and PFOA. The researchers mixed the PFAS chemicals with nZVMs and the porphyrin ring in a buffer solution.

After that, the researchers measured the breakdown of forever chemicals. By analyzing the amount of fluoride ions produced by the reaction, they can tell how much of the PFAS has been degraded.

The result of the study reveals that within five hours, around 75% of the fluoride had been released from branched PFOS and PFOA, indicating a significant reduction of PFAS within the solution. Meanwhile, the catalyst system based solely on B12 showed less than 8% defluorination within the same time period.

In the future, the experts plan to scale up the process in an environmentally friendly way by incorporating it into an electrode. They also hope to utilize this method on linear PFAS and not just on branched types.