Effect of gas composition on pulsed corona discharge characteristics and Hg⁰ removal performance

Plasma technology effectively removes Hg⁰ by oxidizing it via highly reactive species, offering an efficient and rapid approach for mercury emission control. In this work, we investigated the mechanism of Hg⁰(g) removal by pulsed corona discharge non-thermal plasma in pure N₂ and N₂(80%)-O₂(20%) mixtures (or simulated air). Experimental and simulation methods were employed to thoroughly investigate corona discharge electrical characteristics, optical properties, and Hg⁰ removal efficiency, while plasma processes and particle evolution mechanisms were analyzed. Hg⁰ was effectively removed in pure N₂ under pulsed corona discharge, achieving 79% efficiency. Despite discharge instability in simulated air due to oxygen’s electronegativity, its strong oxidizing ability enabled nearly complete Hg⁰ oxidation via enhanced plasma chemistry. Mechanistic analysis indicates that the pulse corona discharge generates abundant high-energy electrons and reactive oxygen species, which play a critical role in the effective removal of Hg⁰. The reactive oxygen species in the N₂-O₂ plasma is suggested to be the key issue for improving the efficiency of Hg⁰ removal. The higher electron temperature in simulated air helps provide sufficient reactive conditions for Hg⁰ removal. This research provides valuable insights into the development of more effective non-thermal plasma systems for Hg⁰ control and enhances the theoretical foundation of plasma technology for Hg⁰ removal.