In the face of looming regulations and growing liability risks, companies are seeking help in managing waste containing per- and polyfluoroalkyl substances (PFAS), also known as “forever chemicals.” Dozens of start-ups are hoping to assist by supplying new technologies capable of destroying the carbon-fluorine bond. Once thought to be impossible to degrade, PFAS are proving to be no match for powerful techniques like electrochemical oxidation and supercritical water oxidation. Companies are also demonstrating that emerging technologies for PFAS destruction, like those that rely on the subcritical process hydrothermal alkaline treatment, plasma, ultraviolet light combined with photocatalysts, and sonolysis can break apart PFAS. When combined with technologies that concentrate PFAS on the front end, destruction technologies could provide a cost-effective way to eliminate PFAS in the environment and stop them from ending up in drinking water.
Scientists once wrongly assumed that the carbon-fluorine bond was almost impossible to break. And that meant there was no practical way to completely destroy per- and polyfluoroalkyl substances (PFAS).
PFAS contamination by the numbers
715
Number of US military sites that the Department of Defense is evaluating for potential contamination by per- and polyfluoroalkyl substances (PFAS)
~3,000
Number of open landfills in the US generating leachate containing PFAS
Nearly 12,000
Number of closed landfills in the US generating leachate containing PFAS
~65,000
Number of public water systems that will have to comply with US Environmental Protection Agency limits for perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) proposed last year
4 parts per trillion
Limit proposed by the EPA for PFOA and PFOS in drinking water
$10.3 billion
Amount to be paid by 3M under a proposed settlement of a lawsuit filed by public water utilities over PFOA and PFOS contamination.
“They were truly thought to be ‘forever chemicals,’ ” says Julie Bliss Mullen, who began investigating technologies for removing PFAS from drinking water as an undergraduate in 2010. At the time, “destruction was not really on the table,” she recalls.
But Mullen was obsessed with breaking the carbon-fluorine bond. PFAS can be removed from water, but they just get transferred to another medium and eventually make their way back into the environment, she says. To stop that cycle, you have to destroy the molecules by breaking the “unbreakable” bond.
Around 2014, as a PhD student at the University of Massachusetts Amherst, Mullen got her hands on some electrodes and, as she puts it, “started playing around with electrochemical oxidation in the lab.” The process creates hydroxyl radicals and, unlike other advanced oxidation techniques, facilitates the direct transfer of electrons. “Those electrons will almost immediately break the carbon-fluorine bond if we’re able to get PFAS onto the anode surface,” she says.
Mullen won’t say how she attracts PFAS to the anode surface. But in 2017, she and the university filed for a patent and spun out a company, Aclarity, to commercialize the technology. Mullen never did finish her PhD. Today, as cofounder and CEO of the Massachusetts-based firm, she’s seeing big interest in the technology from landfill operators and wastewater treatment plants.
Aclarity is not the only company vying for a piece of the PFAS destruction market. Dozens of start-ups are working on technologies for destroying the chemicals, which have been linked to cancer and adverse effects on the liver and immune system. Some companies are already operating at full scale; others are not far behind. And it turns out that electrochemical oxidation is just one of many ways to break the carbon-fluorine bond.
Companies are developing an array of approaches, including supercritical water oxidation, hydrothermal alkaline treatment, plasma destruction, ultraviolet light combined with photocatalysts, and sonolysis. They all claim to break down most PFAS into less harmful chemicals, such as carbon dioxide, fluoride ions, and water. But complete destruction of all PFAS, including short-chain PFAS and precursors, is a stretch for some techniques.
Many of these start-ups are partnering with companies specializing in technologies that remove PFAS from contaminated water and concentrate it. The PFAS destruction start-ups come in at the end and destroy the concentrated PFAS.
It’s early days for PFAS destruction and too soon to tell which technologies will succeed in the marketplace. But entrepreneurs who started these companies see the possibility of permanently ridding drinking water of the once-invincible “forever chemicals.”
No comments:
Post a Comment