The Big Number

A new decontamination process cranks up the heat to remove various contaminants from soil. 

Winter 2024 | By Silvia Cernea Clark

5,432° F

A decontamination process developed by a team of Rice scientists cranks up the heat to 5,432 degrees Fahrenheit to remove organic contaminants and toxic heavy metals from soil. 

Rice chemist James Tour and researchers from the geotechnical structures and environmental engineering branches of the U.S. Army Engineer Research and Development Center have discovered that mixing polluted soil with nontoxic, carbon-rich compounds that carry electrical current and then zapping the mix with short bursts of electricity flushes out both organic pollutants and heavy metals without using water or generating waste. The ultrafast method will be useful in addressing emergency situations.

Photo illustration of a plant with orange color overlay

According to a study published in Nature Communications, the electrical pulses bring soil temperatures to 1,832–5,432 degrees Fahrenheit in seconds, turning organic contaminants into nontoxic graphite minerals and toxic heavy metals into vapor collected via extraction pipes. “Our high-temperature electrothermal process can remove multiple pollutants simultaneously,” says Bing Deng, a postdoctoral research associate in the Tour lab. “This newly established method, which we call high-temperature electrothermal process, or HET, is based on the flash Joule heating technique we developed a few years ago. It is the first time that direct electric heating has been used for soil remediation.” 

This new process regenerates soil while leaving particles and overall mineral composition relatively unchanged. “Plants actually like it more, because of the minerals that get freed up in the thermal cycling,” Tour says. Experiments using the method have showed germination rates to improve by 20% to 30% in remediated soil. 

Yi Cheng, a Rice postdoctoral researcher and lead co-author who helped with the characterization of soil properties, says the process works equally well on wet soil. “Our process is economical and environmentally friendly,” Cheng adds. 

The collaboration between Rice and the Army Engineer Research and Development Center could help the technology transition from the proof-of-concept stage to real-world practice.

James Tour is the T. T. and W. F. Chao Professor of Chemistry and professor of materials science and nanoengineering in the Wiess School of Natural Sciences at Rice.