CAREER: Transforming the synergistic interactions between pyrogenic carbonaceous matter and sulfur species into solutions for contaminant detoxification

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Many halogenated pollutants enter the environment as pesticides, surfactants, and industrial chemicals. These toxic pollutants often end up in the sediment of lakes, rivers, estuaries and the ocean, along with combustion-derived air pollutants like soot and char called pyrogenic carbonaceous matter (PCM). PCM can mix and react with a chemical known as sulfide that naturally exists in many sediments. This project aims to understand how the interaction between PCM and sulfide can degrade halogenated pollutants naturally. The ultimate goal is to use the new understanding of these reactions generated from this research to produce inexpensive engineering solutions that will detoxify pollutants in the sediment and improve human and ecological health. In conjunction with this research initiative will be an educational outreach program targeted at underserved high-school students that will use 3D virtual reality modules and hands-on lab experiences to help students understand how pollutants enter the environment and how natural processes can promote their clean up. A technology-rich and inquiry-based instruction manual will also be developed and distributed to teachers through training workshops and online venues to more efficiently reach the public.There is a pressing need to develop ecologically sound and economically feasible solutions to degrade toxic halogenated pollutants in the environment. These pollutants are found in existing contaminated sites and new halogenated pollutants continue to enter the environment. A recently published study by the PI demonstrates that PCM and sulfide together promote the abiotic degradation of DDT, a halogenated pollutant, which released lower toxicity products. This dehalogenation reaction represents a vast untapped resource for detoxifying pollutants as both PCM and sulfide are naturally occurring in sediment. Yet, due to the complexity that arises from the heterogeneity of the PCM system in the environment, the required conditions for dehalogenation are not understood. This project aims to define these conditions. The specific goals of this project are to: 1) isolate surface functionality, conductivity, and porosity from the complex properties of PCM by synthesizing PCM-like polymers as a model system; 2) characterize the mechanism for the PCM-dependent formation of surface-bound sulfur species using X-ray absorption near-edge structure spectroscopy (XANES); 3) understand how surfaces are involved in dehalogenating contaminants; and 4) investigate the long-term effectiveness of PCM-facilitated dehalogenation in environmental matrices. The results from this project will transform our current understanding of how halogenated pollutants are degraded in the environment by recognizing the abiotic dehalogenation capacities of naturally abundant environmental reagents. An in depth investigation of the speciation and distribution of sulfur species formed on PCM surfaces using XANES will allow for the discovery of a novel reaction pathway that can be harnessed to detoxify pollutants. Moreover, by identifying important PCM properties that are responsible for its reactivity, a new generation of carbon-based materials can be tailored to achieve simultaneous sorption and destruction of pollutants. This will revolutionize current remediation practices by utilizing these carbon-based materials. Lastly, this project will identify the chemical structures that are susceptible to natural breakdown by PCM and inform industry on sustainable chemical designs that minimize environmental impacts. The educational component of this project aims to engage students with diverse learning styles by incorporating innovative instructional strategies, such as developing 3D virtual reality learning modules and employing inquiry-based teaching. The PI will offer a four-week long program each year, entitled ?Water and Pollutants,? to engage high school students from inner city Philadelphia on current environmental issues and engineering solutions. In addition, teacher-training workshops will be organized in the 5th year to promote broader participation and help implement the developed activities into high school classrooms. This project will directly impact approximately 300 undergraduate students, 800 high school students, and 38 high school teachers through the teacher-training workshop.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.