Rice University chemist James Tour has led a research team to develop a rapid electrothermal mineralization (REM) process that, in seconds, can remediate the buildup of synthetic chemicals that can contaminate soil and the environment. The study was published in Nature Communications on July 20.
Per- and polyfluoroalkyl substances (PFAS), or persistent and bioaccumulative pollutants that can accumulate in soil, threaten the environment and human health. PFAS, a large group of synthetic chemicals resistant to heat, oil, water and grease, are used in consumer products such as firefighting foam, food packaging, carpets, cleaning products, paper and paints.
Existing methods for breaking down PFAS are often inefficient, consuming large amounts of energy and water without eliminating these contaminants. The REM process, however, offers a more effective, efficient and environmentally friendly solution.
The REM process uses electrical input to the soil plus biofuel, an environmentally friendly conductive additive, to rapidly heat contaminated soil to over 1000°C in seconds through a pulse of direct current. The intense heat converts PFAS into calcium fluoride, a non-toxic mineral, utilizing the natural calcium compounds present in the soil. This method has demonstrated high removal efficiency (greater than 99%) and mineralization ratios (greater than 90%).
“Our research shows that this high-temperature electrothermal process can effectively mineralize PFAS into nontoxic calcium fluoride,” said Tour, the TT and WF Chao Professor of Chemistry and Professor of Materials Science and Nanoengineering. “The process maintains essential soil properties and improves soil health by increasing nutrient supply and supporting arthropod infiltration.”
This discovery builds on previous work where electrothermal heating was used to vaporize heavy metals and convert organic contaminants in soil into non-toxic graphite materials. In the current study, the research team mixed soil with biochar and applied a pulsating current, achieving rapid heating and mineralization. The effectiveness of the process was confirmed through advanced testing methods, including liquid chromatography-mass spectrometry and ion chromatography.
The REM process stands out for its speed, efficiency, scalability and environmental benefits. The method reduces energy consumption, greenhouse gas emissions and water use compared to existing rehabilitation practices. The lab-scale process can handle up to 2 kilograms of soil per batch, marking an important step toward the larger-scale, field-based application systems currently being designed.
“This method provides a more environmentally friendly and cost-effective approach to soil remediation,” said Yi Cheng, a Rice Academy fellow and postdoctoral research associate in the Tour lab. “We are excited about the potential for field testing and wider deployment in the near future.”
This study was a collaboration between Rice and the US Army Corps of Engineers Research and Development Center funded by a Rice Academy Fellowship, the Air Force Office of Scientific Research and the Army Corps of Engineers.
Other authors include Bing Deng of Rice’s Department of Chemistry, Phelecia Scotland, Lucas Eddy, Karla Silva, Bowen Li, Kevin Wyss, Jinhang Chen, Qiming Liu, Tengda Si, and Shichen Xu; Arman Hassan and Matthew McCary of Rice’s Department of Biosciences; Bo Wang and Michael Wong of Rice’s Department of Chemical and Biomolecular Engineering; Mine Ucak-Astarlioglu and Christopher Griggs of the US Army Corps of Engineers Research and Development Center; Xiaodong Gao, Debadrita Jana and Mark Torres; Materials Science Department at Rice and NanoEngineering’s Khalil JeBailey and Boris Yakobson; and Yufeng Zhao of Corban University.
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