Study On Degradation Mechanism Of Mustard Gas Simulant By Plasma Jet

Sulfur mustard gas（HD）,as a highly toxic and blistering chemical warfare agent（CWA）,has been widely used during World War I and has caused mass casualties around the world.As an emerging green,efficient and stable technology,atmospheric pressure low-temperature plasma has shown great potential in the fields of material science,energy and environment,biomedicine,military and space science,and its application safety has been affirmed.In this study,we developed a low-cost,flexible,stable and safe atmospheric pressure cryogenic plasma jet（APPJ）technology driven by pulsed power and AC power for mustard gas simulant（2-CEES）in liquid phase degradation studies.The research contents of this study are as follows:（1）Mechanism study on the degradation of mustard gas simulants in liquid by pulsed-driven plasma jet.A novel strategy for the removal of sulfur mustard surrogate（2-chloroethyl ethyl sulfide,2-CEES）by pulsed-driven cold plasma jet was proposed in this work.The effects of pulse frequency and pulse width values were varied to optimize the degradation fraction.A high degradation fraction was obtained using a high pulse frequency or a short pulse width.Under optimal conditions,the degradation fraction reached 100%after 3 min of plasma treatment,corresponding to a degradation rate of 3.34μg/min and energy efficiency of 0.4μg/W,respectively.The degradation products include 2-chloroethyl ethyl sulfoxide（2-CEESO）and 2-chloroethyl ethyl sulfone（2-CEESO₂）,these liquid products further turned into gas products（H₂S,HCl,or CO₂）after plasma treatment time of 15 min.Further analysis proved that short-lived excited species such as OH,O,and NO_xand long-lived reactive species（mainly O₃）play an important role in 2-CEES oxidation and mineralization.（2）Mechanism study on the degradation of mustard gas simulants in water by AC-driven plasma jet.A novel strategy for the removal of sulfur mustard surrogate in water by AC-driven cold plasma jet was proposed in this work.The degradation efficiency was optimized by optimizing the AC power parameters,and high power and high frequency were more favorable for the degradation of 2-CEES.When the frequency was 12 k Hz and the power was 10.86 W,the degradation efficiency of 2-CEES（1 mg/ml）reached 100%after APPJ treatment for 5 min.To further explore the factors affecting the degradation efficiency of 2-CEES,the gas flow rate and the initial concentration of 2-CEES were changed.It can be found that the gas flow rate was proportional to the degradation efficiency of 2-CEES,and the initial concentration was inversely proportional to the degradation efficiency of 2-CEES.In addition,in order to explore the degradation mechanism of2-CEES,the active particles generated by the plasma in the liquid phase were first detected,and the effect of these active particles on the degradation efficiency of 2-CEES was studied.Two main short-lived active species（OH and ¹O₂）and long-lived active molecules（H₂O₂）were identified in the liquid phase,and the order of the influence of these three active particles on the degradation efficiency of 2-CEES was obtained:OH>¹O₂>H₂O₂.Finally,the products in the residue of 2-CEES were detected by GC-MS and LC-MS.It was found that these degradation products were also degraded with the further increase of discharge time,it can be concluded that 2-CEES will eventually be degraded into gaseous products,such as SO₂,HCl,CO₂,etc.