How to destroy a “forever chemical”: Scientists are discovering ways to eliminate PFAS

PFAS chemicals initially seemed like a good idea. As Teflon, they made pots easier to clean from the 1940s. They made jackets waterproof and carpets dirt-repellent. Food packaging, fire-fighting foam, and even makeup seemed to perform better with perfluoroalkyl and polyfluoroalkyl substances.

Then tests to detect PFAS in people’s blood began.

Today, PFAS are ubiquitous in soil, dust, and drinking water around the world. Studies suggest they are found in 98% of Americans’ bodies, where they have been linked to health problems such as thyroid disease, liver damage, and kidney and testicular cancer. There are now over 9,000 types of PFAS. They are often referred to as “forever chemicals” because the same properties that make them so useful also ensure that they do not degrade in nature.

Scientists are working on methods to capture and destroy these synthetic chemicals, but it’s not easy.

The latest breakthrough, published in the journal Science on Aug. 18, 2022, shows how a class of PFAS can be broken down into largely harmless components using sodium hydroxide, or lye, an inexpensive compound used in soap. It’s not an immediate solution to this big problem, but it offers new insights.

Biochemist A. Daniel Jones and soil scientist Hui Li working on PFAS solutions at Michigan State University discussed the promising PFAS destruction techniques being tested today.

How do PFAS get from everyday products into water, soil and finally into humans?

There are two main routes of exposure for PFAS to enter humans – drinking water and ingestion.

PFAS can enter soil and leach from landfills through land application of biosolids, ie sludge from wastewater treatment. When contaminated biosolids are applied as fertilizer to agricultural fields, PFAS can enter water and crops and vegetables.

For example, livestock can ingest PFAS through the crops they eat and the water they drink. Cases of elevated PFAS levels in beef and dairy cows have been reported in Michigan, Maine and New Mexico. The extent of the potential risk for humans is still largely unknown.

Scientists in our group at Michigan State University are working on materials to add to soil that might prevent plants from taking up PFAS but would leave PFAS in the soil.

The problem is that these chemicals are everywhere and there is no natural process in the water or soil that breaks them down. Many consumer products are loaded with PFAS, including makeup, dental floss, guitar strings and ski wax.

How are remediation projects now removing PFAS contamination?

There are methods to filter them out of the water. The chemicals stick to activated carbon, for example. But these methods are expensive for large-scale projects, and you still have to part with the chemicals.

For example, near a former military base near Sacramento, California, there is a giant activated carbon tank that takes in about 1,500 gallons per minute of contaminated groundwater, filters it, and then pumps it underground. This remediation project has cost over $3 million, but it prevents PFAS from entering the drinking water used by the community.

Filtering is just one step. Once PFAS is trapped, you need to dispose of activated carbons loaded with PFAS and PFAS is still moving. If you bury contaminated materials in a landfill or elsewhere, PFAS will eventually leach out. That’s why it’s important to find ways to destroy it.

What are the most promising methods scientists have found to break down PFAS?

The most common method of destroying PFAS is by incineration, but most PFAS are remarkably resistant to incineration. That’s why they’re in fire-fighting foams.

PFAS have multiple fluorine atoms bonded to a carbon atom, and the carbon-fluorine bond is one of the strongest. Normally, to burn something you have to break the bond, but fluorine resists breaking carbon. Most PFAS are completely degraded at incineration temperatures around 1,500 degrees Celsius (2,730 degrees Fahrenheit), but it is energy intensive and suitable incinerators are scarce.

There are several other experimental techniques that show promise but have not been scaled up to treat large volumes of the chemicals.

A group at Battelle has developed supercritical water oxidation to destroy PFAS. High temperatures and pressures change the state of water and accelerate chemistry in ways that can destroy hazardous substances. However, scaling remains a challenge.

Others work with plasma reactors that use water, electricity and argon gas to break down PFAS. They are fast, but also not easy to scale.

The method described in the new article, led by Northwestern scientists, shows promise for what they’ve learned about breaking down PFAS. It will not be scaled up to industrial treatment and uses dimethyl sulfoxide or DMSO, but these results will guide future discoveries of what might work.

What are we likely to see in the future?

Much will depend on what we learn about where most human exposure to PFAS comes from.

If exposure is primarily through drinking water, there are other methods with potential. It’s possible that it could eventually be destroyed at the household level using electrochemical methods, but there are also potential risks that have yet to be understood, such as: B. the conversion of common substances such as chloride into more toxic by-products.

The big challenge in remediation is making sure we don’t make the problem worse by releasing other gases or creating harmful chemicals. Humans have a long history of trying to solve problems and making things worse. Refrigerators are a good example. Freon, a chlorofluorocarbon, was the solution to replacing toxic and flammable ammonia in refrigerators, but then it caused stratospheric ozone depletion. It has been replaced by fluorocarbons, which are now contributing to climate change.

If there’s one lesson to be learned, it’s that we need to think through the entire product life cycle. How long do we really need chemicals?

A. Daniel Jones, Professor of Biochemistry, Michigan State University and Hui Li, Professor of Environmental and Soil Chemistry, Michigan State University

This article was republished by The Conversation under a Creative Commons license. Read the original article.

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