Hydrofluorocarbon Greenhouse Gas Mineralization via Oxidative Low-Temperature Plasma

Hydrofluorocarbons (HFCs) are potent greenhouse gases with 100-year global warming potential up to 12,400 times that of CO2. Due to their recalcitrant C–F bonds, waste HFC refrigerants are typically remediated in intensive high-temperature facilities. Herein, we investigated two low-temperature, atmospheric-pressure plasma processes for remediating three common HFCs: CH2F2 (HFC-32), CHF3 (HFC-23), and CH2FCF3 (HFC-134a). First, we studied HFC degradation in a dielectric barrier discharge (DBD) reactor with a downstream alkaline trap. Addition of oxidants including CO2, O2, and, to a lesser extent, water vapor enhanced mineralization to fluoride. Therefore, we employed a low-temperature arc utilizing the alkaline absorbent as the ground electrode to produce reactive oxygen species. Compared to DBD, the arc significantly increased single-pass HFC degradation to 71.4% for CH2FCF3, 88.7% for CHF3, and 91.3% for CH2F2, with 80.0–99.9% conversion to fluoride. Therefore, the plasma-water arc could enable modular and decentralized HFC remediation. The insights into radical chemistry at the plasma-water interface offer broader mechanistic understanding for degradation of recalcitrant halogenated organic contaminants.