Hydrothermal Destruction of PFAS during Designer Biochar Reactivation

Per- and Polyfluoroalkyl Substances (PFAS) are a class of man-made chemicals and have been used in firefighting foams, non-stick coatings, paper products, textiles, and many other commercial products. However, PFAS are highly resistant to biotic and abiotic degradation, can withstand very high temperatures, and readily bioaccumulate and endanger public health and environment. Currently, the widespread occurrence of PFAS in the environment has been recognized as an emerging issue.

Numerous treatment technologies have been developed to remove PFAS. Typically, activated carbon is the most common and feasible technology to filtrate PFAS from drinking water. Biochar is a carbon rich material produced from biomass like forestry or agricultural residues by pyrolysis, making it a less expensive sorbent compared to activated carbon.

While both biochar and activated carbon are excellent for removing PFAS from water, handling these spent adsorbents is a big challenge. If PFAS-laden filters are put into a landfill, PFAS could desorb and discharge back into the water and soil surrounding the landfill. Incineration has been a common way to treat PFAS-laden material. However, the incineration of PFAS poses issues due to PFAS compounds commonly breaking down into smaller, less manageable PFAS compounds during this process. Because of this, as of April 26, 2022 the Office of the Assistant Secretary of Defense has put a temporary ban on the incineration of PFAS compounds until a safe disposal guidance can be issued to comply with the National Defense Authorization Act of 2022.

ISTC researcher Wei Zheng received a grant from the US Department of Defense’s (DoD) Strategic Environmental Research and Development Program (SERDP) to develop low-energy hydrothermal technology to destroy PFAS bound to biochar and at the same time reactivate the biochar for reuse. This project will address multiple stages of the remediation strategy:

  1. Create a low-cost designer biochar that will efficiently capture PFAS from contaminated waters.
  2. Develop a low-energy hydrothermal treatment system for the destruction of PFAS as well as researching their decomposition mechanisms.
  3. Reactivate the PFAS-laden biochar without eliminating the ability of the biochar to remove PFAS in the future.

There is currently a lack of knowledge concerning the safe destruction of PFAS. The technique developed in this project provides a novel, efficient, and economical adsorbent to remove PFAS from contaminated water, but also completely destruct PFAS and regenerate the adsorbent. The impact of this research could be widespread as the scientific community continues to learn more about this family of chemicals and how to properly remediate and dispose of PFAS. It will also help federal and state agencies improve their management strategies concerning PFAS. The SERDP project started in February 2023 and will be funded through January 2027.

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