Effect of crystallographic structure of MnO2 on degradation of 2-CEES

In this study, four MnO2 samples with different crystallographic structures (alpha-, beta-, delta- and gamma-MnO2) were synthesized by the hydrothermal method. The relationship between the characteristics of the four crystalline samples and their degradation ability against 2-chloroethyl ethyl sulfide (2-CEES), a simulant of the chemical warfare agent sulfur mustard, and the relevant reaction mechanism were investigated. Characterization data indicated that the various crystal types displayed different specific surface areas, frequency of lattice defects, amounts of adsorbed/inserted water, and numbers and strength of basic sites. The combined effects of these differences caused different degradation activity in 2-CEES degradation to be observed. The reaction followed pseudo-first-order kinetics, whereby gamma-MnO2 exhibited the highest degradation activity. The mechanism of 2-CEES degradation was studied by gas chromatography and infrared spectroscopy methods, and data indicated the key role played by substrate hydrolysis and oxidation in the degradation process. (C) 2021 Elsevier B.V. All rights reserved.