(402c) Biochar-Enabled Advanced Reduction Process for Enhanced Sorption and Degradation of per- and Polyfluoroalkyl Substances (PFAS) in Water

Per- and polyfluoroalkyl substances (PFAS) are manmade chemicals that are increasingly detected in the environment. PFAS exposure at low concentrations (e.g., ng/L) has been linked to various adverse effects on human health and the environment, so removing PFAS from the environment is urgently needed. However, due to the strong carbon-fluorine (C-F) bond in PFAS molecules, PFAS destruction is extremely challenging. The advanced reduction processes (ARPs) that generate reactive reducing radicals have been identified as an effective approach to breaking down the C-F bonds in PFAS by reductive reactions. We have been working on the development and optimization of ARPs for PFAS destruction and defluorination in water over the past years. We found that up to ~100% destruction efficiency and ~85% defluorination efficiency for different long-chain and short-chain PFAS in water can be achieved by the ARPs. The ARPs were sensitive to solution chemistry (e.g., pH, dissolved oxygen, and sulfite dosage) that controls the species and yield of reducing radicals responsible for PFAS destruction and defluorination. Adding biochars and modified biochars before ARPs was observed to enhance the destruction and defluorination efficiencies of PFAS in water due to the: (1) enhanced sorption (preconcentration) of PFAS on biochar surfaces; and (2) prolonged longevity for reducing radicals for extended reductive reactions between PFAS molecules and reducing radicals. These findings demonstrate that the ARPs, assisted by biochars, can be used as a viable strategy for the deep destruction and defluorination of various PFAS in water.