Major products and their formation and transformation mechanism through degrading UDMH wastewater via DBD low temperature plasma

Unsymmetrical dimethylhydrazine (UDMH) is a liquid propellant widely used in aviation and aerospace. It produces a large amount of dimethyl hydrazine wastewater during long-term storage, testing, and reinjection. Traditional treatments produce numerous secondary contaminants such as residual high carcinogens, including N-nitrosodimethylamine (NDMA) and formaldehyde dimethylhydrazone (FDMH). In this paper, the dielectric barrier discharge (DBD) low temperature plasma technology is used to degrade the dimethyl hydrazine wastewater. Aiming at the problem of secondary pollutants in the degradation process, we used qualitative and quantitative methods to study the changes of NDMA and FDMH during the degradation of dimethyl hydrazine wastewater by DBD low temperature plasma. The kinetics of these two products showed that the degradation process of NDMA was consistent with the first-order reaction kinetics. Using density functional theory, we established molecular models of UDMH, NDMA and FDMH. According to the molecular orbital theory, the formation mechanism of NDMA and FDMH was calculated from three aspects: reaction structure, reaction path and energy change. We found that during the degradation of dimethyl hydrazine, the dimethyl hydrazine oxidation product was initiated by hydrogen abstraction on methyl (-CH3) and amine (-NH2). NDMA is produced by the oxidation of -NH2, whereas FDMH is mainly produced from dimethyl hydrazine and formaldehyde.

Automated summary

In this study, the dielectric barrier discharge (DBD) low temperature plasma technology was used to degrade dimethyl hydrazine wastewater. Qualitative and quantitative methods were used to study the changes of NDMA and FDMH during the degradation process. The formation mechanisms of NDMA and FDMH were calculated using density functional theory and molecular orbital theory. Through the research, it was found that NDMA is produced by the oxidation of -NH2, while FDMH is mainly produced from dimethyl hydrazine and formaldehyde.