ERASE-PFAS: Boosting mass transfer for PFAS electrooxidation through enhanced electro-migration

Per- and poly-fluoroalkyl substances (PFAS) are a group of over 12,000 artificial chemicals. Because of their excellent stability, PFAS are widely used in commercial products and industry. Unfortunately, widespread PFAS use has resulted in environmental contamination. This problem is made worse by the extreme resistance of PFAS to breakdown. For this reason, PFAS are sometimes referred to as “forever chemicals.” It is estimated that over 80% of drinking water sources in the USA are contaminated by PFAS at concentrations potentially harmful to human health. The magnitude of this public health issue has led to research focused on developing effective approaches to treat PFAS contamination. Electrochemical oxidation (EO) shows promise as an efficient and cost-effective method for the destruction of PFAS in water. In EO, the transport of PFAS from bulk water to the reaction surface (the anode) limits the rate at which PFAS can be destroyed. Modifying the anode with thin tips on the surface creates a locally enhanced electric field treatment (LEEFT) that increases the electric field strength thousands of times. While LEEFT can increase electric-field driven PFAS transport (and thus greatly enhance the efficiency and rate of PFAS destruction), there are significant knowledge gaps regarding PFAS electromigration and destruction that prevent optimization of the process. This project will address these knowledge gaps by investigating the destruction of various PFAS on anodes with different structures under different electric field strengths. Successful completion of this project has great potential to benefit society through the development of LEEFT technology to improve PFAS destruction with significantly reduced cost. Additional benefits to society result from training and outreach to increase scientific literacy and help develop the Nation’s STEM workforce. Although EO is among the most efficient and cost-effective methods for PFAS degradation, the approach is limited by suboptimal degradation efficiency. Improving total PFAS mass transport to the anode has been proven effective to achieve higher PFAS degradation efficiencies. Although total mass transport is the sum of diffusion and electromigration, researchers generally seek to optimize diffusion while ignoring the contribution of electromigration due to the typically low electric field strength under most operational conditions. LEEFT can significantly enhance electric field strengths by several orders of magnitude under low voltages, creating electromigration flux comparable to or surpassing that of diffusion. The goal of this project is to systematically study the influence of electric field strength on PFAS electromigration, EO degradation of PFAS, and the combined efficacy of LEEFT in enhancing electromigration and degradation. The degradation of various PFAS by Ti4O7, anodes with different surface morphologies will be investigated. A feature of this project is the focus on addressing environmentally-relevant PFAS concentrations ranging from nanogram to milligram per liter. The effects of background anion concentrations on PFAS destruction will be assessed to evaluate the treatability of this process. Successful completion of this project will facilitate translation of research outcomes into practical applications for PFAS treatment. New knowledge gained from this project will be integrated into summer programs tailored for K-12 students that focus on exploring and addressing complex societal challenges with significant impacts. 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.