LAWRENCE — A scholarly report in the journal Science Advances from researchers at the University of Kansas shows a new eco-friendly method for separating the chemicals found in common refrigerants for easier recycling at industrial scale.
"The motivation of this work is to enable separation of highly complex gaseous refrigerant mixtures," said lead author Abby Harders, who performed the research as a KU doctoral student in the research group of co-author Mark Shiflett, Foundation Distinguished Professor of Chemical and Petroleum Engineering. "This effort has been driven by climate legislation phasing out certain hydrofluorocarbon (HFC) refrigerants."
The paper's key innovation uses membranes — amorphous fluorinated polymers, to be specific — that efficiently isolate complex refrigerant mixtures. Other separation methods, like distillation, are less effective because of the complex composition of the mixtures. Harders said the membranes are fabricated to allow some gases to pass through while restricting others — resulting in effective purification.
To demonstrate the technology could scale to industrial viability, the team — including many associated with KU's Wonderful Institute for Sustainable Engineering — developed a custom-coating process to create submicron coatings on the membrane's porous supports, creating composite hollow fibers. The results show a functional prototype, proving the technology's usefulness to firms engaged in refrigerant recovery and reuse.
Harders cited international agreements and legislation like the Kigali Amendment to the Montreal Protocol and the American Innovation and Manufacturing Act that will phase out HFC production as the ultimate solution to atmospheric warming from refrigerants. In the meantime, however, solutions for dealing responsibly with complex gases in existing equipment destined for landfills around the world are badly needed, she said.
For example, according to the U.S. Environmental Protection Agency, HFC-134a, the most common refrigerant used in MVAC systems today, is a "potent greenhouse gas with a global warming potential that is 1,430 times that of CO2."
Harders said economically viable solutions for recycling the heat-trapping gases will keep more of them from release into Earth's atmosphere.
"A large percentage of refrigerant today is not recovered — it's simply vented into the atmosphere," she said. "Much of this occurs when equipment is decommissioned. In some cases, recovering refrigerant may not seem worthwhile, or those responsible for recovery may not recognize its value. Additionally, if refrigerant is not fully evacuated, it can end up in landfills, where it eventually leaks into the atmosphere. Approximately 90% of refrigerant leakage occurs at the end of a system's life."
The KU researcher said she hopes the method she largely devised in her time at KU could help bridge the gap ahead of the next generation of refrigerants.
"To increase reusability and allow for the extraction and recycling of HFC refrigerants from end-of-life units, it's essential to separate them effectively so they can be purified and reintroduced into the market," she said. "However, no existing industrial technology can currently achieve this. These refrigerants form complex mixtures that cannot be separated using traditional heat-driven methods like distillation."
Today, Harders works as a chemical engineer and head of research and development with Lawrence-based Icorium Engineering , a startup that emerged from the Shiflett Research Group situated in KU's Innovation Park . While Icorium focuses on separation of refrigerants using ionic liquids, the new method demonstrated in Harders' paper offers a new tool to the industry.
"Part of Abby's Ph.D. research at KU is now being translated into the startup company," said Shiflett, who co-founded Icorium and now serves as its chief science officer. "Abby also has a fascinating education journey. She earned her undergraduate degrees in chemistry and mathematics at Bethel College in central Kansas, participated in an NSF-sponsored Research Experience for Undergraduates during 2019 in my lab and then came to KU for her Ph.D. in chemical engineering. She was an amazing student, receiving the Chancellor's Doctoral Fellowship for her doctoral research and graduating with a 4.0 GPA at the top of her class. She's published 10 papers and is a co-inventor on a patent application. Needless to say, I'm very proud of her and her research and journey."
Harders and Shiflett's co-authors on the paper were Luke Wallisch, Michael Lundin and Ed Atchison of the Wonderful Institute for Sustainable Engineering at KU, Chloe Le of California Polytechnic State University, Gabrielle Zaher of the University of Washington, and Whitney White of Warren, New Jersey-based Chromis Technologies.
For Harders, whose generation will face yet more severe challenges from a warming climate, the chance to bring her engineering expertise to fight the climate crisis has personal meaning.
"I feel like I'm doing work that not only will impact me or future kids I might have, but something that can hopefully impact a lot of people's lives," she said. "That's something that really helps me stay motivated, not get burnt out, because what I'm doing will hopefully continue to be well received by policymakers and have industrial value. Eventually, we'll have full-scale commercial use so that it can actually do what it's intended to do and make the impact that we want it to make."
