First commercially produced in the 1940s, the family of per- and polyfluoroalkyl substances (PFAS) known today boasts thousands of members. The rock-solid carbon-fluorine bonds guarantee thermal and chemical stability, while other chemical groups make them repel water, oil and fats. This is why they are a mainstay in so many industrial and consumer products.
The three-step process begins with filtration and concentration steps before destruction in a bottle-shaped reactor.
Here, a photochemical process operating at room temperature and pressure breaks down PFAS compounds into free fluoride and carbon dioxide.
Claros says the photochemical system achieves over 99% destruction of all PFAS compounds, including ultrashort chains (C1-C3), within 1-3 hours. The company adds that energy use and cost studies show the system to be the most efficient process available when compared with hydrothermal and electrochemical processes.
Designed as a low-energy, small-footprint process, it can be used in both batch and continuous modes and can be scaled up with what the company describes as low Capex and energy costs.
It currently comes in 5-liter, 10-liter and 100-liter batch reactors, with 1,000-2,000 liter systems available on request.
In addition, Claros recently has obtained ISO/IEC 17025 certification and possesses advanced analytical capabilities, which enables the company to provide a one-stop solution for PFAS treatment that includes analysis, removal and destruction services by combination.
Kureha’s interest is not new, with the two organisations working on a collaboration for a few years now. The latest investment will accelerate this work, including scaling up the system and associated business development to become a pioneer of industrial scale PFAS destruction in Japan and Taiwan.
“We will try our best to deliver the system to the market as early as possible utilizing each of our strengths,” noted Kureha America President and CEO Naomitsu Nishihata.
‘Halting’ PFAS Using an Alkali Catalyst
Aquagga, based in Tacoma, Washington, uses a patented process called hydrothermal alkaline treatment (HALT) for the complete destruction of PFAS.
The patent describes a process that combines PFAS with an alkali, such as sodium hydroxide, which is then heated and pressurised in a sealed reactor. These conditions break the C-F bonds, turning PFAS in their building blocks, including sodium carbonate, sodium fluoride and sodium sulphate.
Aquagga describes its process as being similar to super critical water oxidation but says using alkali as a catalyst allows the process to be operated at much lower temperatures, pressures and with much less process complexity.
The process originally was developed by the Colorado School of Mines where researchers were fine-tuning a technique for renewable energy generation that relied on heating algae or wastewater sludge under high pressure to essentially speed up the natural geochemical processes that create hydrocarbon fuels.
Wondering whether a similar strategy could be used to deal with PFAS, they found that adding strong alkalis to the mixture before heating was very effective.
The school then entered into an exclusive licensing agreement with Aquagga, itself a spin out of the University of Alaska Fairbanks and University of Washington, to commercialize the HALT.
In the last four years Aquagga has raised nearly $4 million in funding, including Phase II small business innovation research (SBIR) contracts with the EPA and The Defense Advanced Research Projects Agency, or DARPA, and over $750,000 in private investment.
The company currently offers the technology in mobile units capable of three different treatment rates: 1-2 gallons/hr, 10-20 gallons/hr, and 50-150 gallons/hr.
Renewable PFAS Adsorbents
A quite different approach is being taken by Cyclopure in Chicago. This company has developed a novel adsorbent known as Dexsorb, which has high selectivity for PFAS removal, regardless of chain length, structure or functional group.
Starting with corn starch, an enzymatic biotransformation converts this to beta cyclodextrin. Following a one-stop polymerisation process, cyclodextrin is produced. It’s the 0.78 nm crevices or “cups” within this molecule that give the high molecular selectivity for PFAS.
Trillions of such cups in each gram of Dexsorb create a network of uniform pore structures with rapid uptake and a high capacity, more than 10 times than what’s available in activated carbon, according to the company.
"A lot of attention is being given to destruction technologies, which are required to prevent PFAS from re-entering the environment,” explains CEO Frank Cassou. “But, a back-end destruction technology requires a highly effective front-end removal technology for complete PFAS elimination."
Operators of large-scale engineered systems across the U.S. are installing the technology, including one running at 250 gallons/minute, Cassou says. The company also has a bid in for a 14 million gallon/day project.
In addition, Cyclopure recently won approval for its technology from the Massachusetts Department of Environmental Protection to remove PFAS6 chemicals from drinking water. The approval is effective statewide for use in all four of the department’s regions.
The issue is more than skin-deep
Meanwhile, revelations about PFAS continue to emerge in the peer-reviewed literature.
In June, research published in Environment International found that 17 commonly used PFAS can be absorbed readily through human skin.
Carried out in the U.K. by researchers at the University of Birmingham’s School of Geography, Earth and Environmental Sciences, the findings are notable for several reasons.
"The ability of these chemicals to be absorbed through skin has previously been dismissed because the molecules are ionized,” says study co-author Oddný Ragnarsdóttir. “The electrical charge that gives them the ability to repel water and stains was thought to also make them incapable of crossing the skin membrane.”
The research shows this theory doesn’t always hold true and that uptake through the skin could be a significant source of exposure to PFAS she adds.
Of the 17 PFAS tested, all of which are regulated by the EU's Drinking Water Directive,
15 substances showed substantial dermal absorption – at least 5% of the exposure dose. At the exposure doses examined, absorption into the bloodstream of the most regulated PFAS, PFOA, was 13.5% with a further 38% of the applied dose retained within the skin for potential longer-term uptake into the circulation.
The amount absorbed seemed to correlate with the length of the carbon chain within the molecule. Substances with longer carbon chains showed lower levels of absorption, while compounds with shorter chains that were introduced to replace longer carbon chain PFAS like PFOA, were more easily absorbed. Absorption of perfluoropentanoic acid, for example, was four times that of PFOA at 59%.
"This study helps us to understand how important exposure to these chemicals via the skin might be and also which chemical structures might be most easily absorbed,” says study co-author Stuart Harrad. “This is important because we see a shift in industry towards chemicals with shorter chain lengths because these are believed to be less toxic. However, the tradeoff might be that we absorb more of them, so we need to know more about the risks involved."
A month earlier a study published in Eco-Environment & Health highlighted the levels, health risks and transport protein binding capabilities of PFAS in early life.
The researchers, led by a team from School of Public Health at Fudan University in Shanghai, China, analyzed six types of PFAS in 1,076 mother-child pairs. They found PFOS was most prevalent in maternal serum, while placental transfer efficiency of PFAS was higher than breastfeeding transfer, suggesting that these chemicals are more likely to cross the placenta and accumulate in the fetus.
Their findings prompted the researchers to call for tighter PFAS regulations and further research into their environmental and health effects.
