Nitrosonium

Abstract: The chemical interaction between non-thermal plasma species and aqueous solutions is considered in the case of discharges in humid air burning over aqueous solutions with emphasis on the oxidizing and acidic effects resulting from formed peroxynitrite ONOO− and derived species, such as transient nitrite and stable HNO3. The oxidizing properties are mainly attributed to the systems ONOO−/ONOOH [E°(ONOOH/NO2) = 2.05 V/SHE], ·OH/H2O [E°(·OH/H2O) = 2.38 V/SHE] and to the matching dimer system H2O2/H2O [E°(H2O2/H2O) = 1.68 V/SHE]. ONOOH tentatively splits into reactive species, e.g., nitronium NO+ and nitrosonium NO 2 + cations. NO+ which also results from both ionization of ·NO and the presence of HNO2 in acidic medium, is involved in the amine diazotation/nitrosation degradation processes. NO 2 + requires a sensibly higher energy than NO+ to form and is considered with the nitration and the degradation of aromatic molecules. Such chemical properties are especially important for organic waste degradation and bacterial inactivation. The kinetic aspect is also considered as an immediate consequence of exposing an aqueous container to the discharge. The relevant chemical effects in the liquid result from direct and delayed exposure conditions. The so called delayed conditions involve both post-discharge (after switching off the discharge) and plasma activated water. An electrochemical model is proposed with special interest devoted to the chemical mechanism of bacterial inactivation under direct or delayed plasma conditions.

Abstract: The dynamic character of the active centers has made it difficult to unravel the reaction path for NH3-assisted selective catalytic reduction (SCR) of nitrogen oxides over Cu-CHA. Herein, we use density functional theory calculations to suggest a complete reaction mechanism for low-temperature NH3-SCR The reaction is found to proceed in a multisite fashion over ammonia-solvated Cu cations Cu(NH3)(2+) and Bronsted acid sites. The activation of oxygen and the formation of the key intermediates HONO and H2NNO occur on the Cu sites, whereas the Bronsted acid sites facilitate the decomposition of HONO and H2NNO to N-2 and H2O. The activation and reaction of NO is found to proceed via the formation of nitrosonium (NO+) or nitrite (NO2-) intermediates. These low-temperature mechanisms take the dynamic character of Cu sites into account where oxygen activation requires pairs of Cu(NH3)(2+) complexes, whereas HO-NO and H3N-NO coupling may occur on single complexes. The formation and separation of Cu pairs is assisted by NH3 solvation. The complete reaction mechanism is consistent with measured kinetic data and provides a solid basis for future improvements of the low-temperature NH3-SCR reaction.