Degradation of particulate matter utilizing non-thermal plasma: Evolution laws of morphological micro-nanostructure and elemental occurrence state

Particulate matter (PM) is harmful to the environment and human health. It is of practical significance to explore green and sustainable technologies for efficient removal of PM by studying the mechanism of PM oxidation and decomposition. A visualization test system for oxidatively decomposing diesel PM using non-thermal plasma (NTP) was developed to perform oxidative decomposition tests on PM samples at different lengths of time at 120 °C. The physical and chemical properties of primary particles, elemental carbon (EC) oxidation activity, and surface functional groups of the PM at different oxidation stages were analyzed to investigate how micro-nanostructure changes of PM affected the oxidation characteristics and elemental occurrence. The structure of primary particles was divided into three parts: in-core, ex-core, and ex-core edge. A dynamic nanostructure model of primary particles was established during the reaction process. The primary particles experienced the evolution process of 'massive removal of crystalline at the outer edge of the nucleus', 'disordered arrangement of crystalline' and 'hollow crystalline in the nucleus after erosion ', corresponding to the early, middle and late stages of oxidation, respectively. The nanostructure properties of PM changed non-linearly during the decomposition of PM by NTP, and there was a linkage effect among the microcrystalline parameters, oxidation activity, and elemental distribution of PM. •Visualization test equipment was built to observe the oxidative decomposition of PM.•The nonlinear microscopic properties of PM directly affected NTP reaction sensitivity.•The three-stage innovative model for carbon particle oxidation by NTP was revealed.•A correlation was observed between the nanostructure and oxidation characteristics of PM.