Plasma discharge synthesis of nitrite ions NO2– for wastewater treatment from water-soluble compounds of reactive nitrogen

Abstract

Currently, there is a critical situation of high matter of water-soluble nitrogen compounds in water bodies of developed countries. In world practice, it is believed that the most promising method for removing nitrogen compounds from wastewater is anammox technology based on the biochemical process of oxidizing ammonium with nitrite under anoxic conditions. Bacterial anammox is based on the reaction between nitrite ion and ammonium ion, which converts them to molecular nitrogen. However, anammox bacteria are characterized by a low growth rate and require specific growing conditions. As an alternative to the bacterial anammox technology, there is proposed a technology of plasma microwave-discharge synthesis of nitrite ions NO2– from air, carried out in a microwave plasma in a magnetron-type plasmatron for purifying waste water from water-soluble compounds of reaction nitrogen. The unique possibilities of non-equilibrium low-temperature plasma, as a medium for chemical reactions, and, in particular, in microwave plasma, are the basis of new promising technologies. Under the conditions of microwave discharge turbulence, ionized molecules of nitrogen N2+ and oxygen O2–, approaching each other, interact, it triggers an avalanche-like cascade of reactions with the formation of two molecules of nitrogen monoxide NO, which is starting for the transition from the electron shock stage of plasma chemical reactions to the stage of avalanche-like photolytic synthesis of nitrogen oxides NOx. Based on the results of studying the concentration of the final products of plasma chemical reactions in the microwave discharge zone, the synthesis of nitrite ions of NO2– is predominant. Experimental studies were carried out on the effect of the NO2– nitrite ion stream obtained at the plasmatron outlet on a model solution of ammonia hydrate (NH4OH) at a concentration of 150 mg/l. The most optimal was the time of exposure of ionized gas to the model solution for 5 minutes, while the efficiency of removing ammonium ions was 99.83%. Thus, plasma microwave-discharge synthesis of nitrite ions NO2– can be an alternative to biological anammox technology and is characterized by simple and compact installation.

Keywords

• nitrogen
• wastewater
• anammox technology
• ammonia hydrate
• microwave discharge plasma
• synthesis of nitrite ions