Project Summary (2025-2030)

There is a pressing need for more reliable and cost-effective remediation of contaminated soils and sediments at Superfund sites to mitigate exposure and protect public health. This project will develop a sustainable thermal remediation technology to rapidly and reliably treat soils contaminated with such priority pollutants, including activated PAHs byproducts of environmental transformations. Similar to all other thermal remediation technologies, high energy requirements are a major cost driver that hinders its scalability and broad application. Thus, significantly decreasing energy requirements for thermal treatment is a critical goal (and anticipated benefit) of this project. In previous studies, the team made significant novel scientific contributions: (a) Discovery of a new pyrolytic degradation pathway that degrades PAH by anoxic heating and eventually converts them to a stable and non-toxic (char-like) carbonaceous residue, which is a safe treatment endpoint. (b) Recognition of the importance of soil components like clays, which can catalyze PAH decomposition reactions, apparently facilitated by π-cation interactions between PAHs with transition metals. (c) Use of a combined mathematical and experimental approach to analyze soil behavior and soil-contaminant interactions during pyrolytic treatment, and derive the kinetics of decomposition reactions. This framework allows the researchers to study potential tradeoffs between PAH degradation efficiency, energy requirements, and residual toxicity of treated soils due to toxic byproducts potentially forming at low temperatures.

Thus, the Specific Aims are to:

1. Understand and exploit the catalytic effect of natural clays with common transition metals (e.g., Fe, Cu) to accelerate the pyrolytic degradation of PAHs, detoxify the contaminated soils and decrease the required treatment temperature, time, and energy.

2. Apply molecular modeling with density-function theory to advance molecular-level understanding of PAH proximal adsorption and degradation mechanisms on catalytic sites, and characterize pathways and byproducts to guide safe application.

3. Develop a process model for designing and optimizing pyrolysis reactors.

The hypothesis is that pyrolytic treatment of contaminated soils under carefully selected conditions will consistently achieve regulatory compliance and completely eliminate toxicity while recovering soil fertility to facilitate ecosystem restoration. Furthermore, clays enriched with common transition metals will catalyze pyrolytic degradation of PAHs and decrease the required temperature and contact time to significantly lower the energy requirements. Overall, this project will advance molecular-level understanding of PAH degradation in pyro-catalytic treatment systems and enable predictive understanding of contaminant/soil interactions and reaction mechanisms. Thus, this project will inform the design of thermal treatment processes with lower energy requirements, higher throughput capacity, and wider applicability.