Collaborative Research: ECO-CBET: Plasma-Assisted Dehalogenation of Persistent Halogen-Containing Waste Streams

The “take-make-dispose” model for the utilization of halogen-containing compounds has polluted the planet’s water, soil, and air resources. The strong carbon-halogen bonds resulting from halogens being potent oxidants have resulted in a contamination challenge with a daunting legacy. Chlorofluorocarbons (CFCs), which were globally banned 30 years ago to close the Antarctic ozone hole, persist in the atmosphere. Additionally, there are over 9000 poly- and perfluoroalkyl substances (PFAS) currently contaminating rainwater worldwide, and polyvinylchloride (PVC) plastics account for more than 50% of chlorine found in municipal waste. Today, xenobiotic organohalogen compounds are pervasive: PFAS-contaminated water is consumed by 200 million Americans and PVC is the primary contributor to the nation’s annual dioxin burden, surpassing that of any other industrial product. To address this legacy contamination challenge, a step change solution is required, one that surpasses the limited scope of current thermochemical technologies. In this project, plasma-assisted dehalogenation is proposed as a disruptive solution to this challenge. The project focuses on the use of non-equilibrium plasmas for the degradation and recycling of halogen-containing waste and holds enormous potential for improving human health and preserving the environment. This convergent research project will provide unique opportunities for interdisciplinary STEM education and training and prepare a diverse pipeline of students and researchers to become the next generation of interdisciplinary scientists and engineers. Planned outreach activities involve the development of hands-on activities for K-12 programs, with a focus on at-risk and often underrepresented students. The effort involves partnerships with industry to further technological development and activities that raise awareness among local communities about the pervasive presence of halogen-containing compounds and the associated health and safety challenges they pose. The goal of the research is to probe at a mechanistic level plasma-assisted dehalogenation reaction chemistry and to use these insights to develop innovative processes that make possible recycling of reaction products or the full mineralization of haloginated components. Non-equilibrium plasma refers to a partially ionized gas operating at near ambient temperatures, where only the electrons possess kinetic energies high enough to enable the production of short-lived reactive species which act as initiators for chain reactions of various substrates. This convergent research program leverages the PIs’ expertise in chemical reaction engineering, plasma science, chemical modeling and theory, and environmental engineering to establish a plasma dehalogenation model that will be used to design a reactor for plasma-assisted dehalogenation of waste streams with a focus on PFAS and PVC as two testbed cases. The successful completion of this research will lead to new fundamental scientific insights and engineering solutions contributing to a broader framework for dehalogenating a wide range of waste streams. 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.