Plasma treatment on flame soot: view from nanostructure and reactivity of soot

Abstract

In recent years, the use of plasma for pollutant emission control has an expected potential. In this study, soot particles from flames were sampled from an ethylene inverse diffusion flame, which were placed in a self-designed dielectric barrier discharge plasma device for reaction treatment. The nanostructure and oxidation reactivity of soot particles after plasma treatment were evaluated by transmission electron microscopy, Raman spectroscopy, X-ray diffraction analysis and X-ray photoelectron spectroscopy. With 16 kV, 2.5 kHz as an example, with the treatment of plasma, the fringe length decreases (1.3% and 9.6%), and the fringe tortuosity increases (1.1% and 8.7%) in both high-maturity and low-maturity soot particles, which means that the oxidation activity of soot is enhanced after plasma discharge. Raman spectra, X-ray diffraction analysis spectra and X-ray photoelectron spectroscopy spectra have confirmed this phenomenon, especially the oxidation activity of soot particles under the action of plasma at high maturity is more obvious. It is worth noting that the enhancement of soot oxidation activity after plasma discharge has certain limitations, that is, the oxidation activity will not continue to increase after it is enhanced to a certain intensity, which may be related to the selection of Ar as the atmosphere gas.