Capture of NH3 using air plasmas to form NH4NO3 for N recycling: Impact factors and mechanisms

Ammonia loss results in significant resource waste and environmental pollution. In this study, we proposed and explored the way of using air plasmas to capture NH3 to form NH4NO3 for N recycling under different reaction modes, discharge powers, and gas flow rates. The reaction mechanisms under different modes were also revealed. A needle-needle discharge driven by AC power was used and ammonia gas was utilized to simulate the volatilized ammonia. Notably, white particles were observed during Mode 1 and Mode 2 (these particles gradually disappeared over time in Mode 2), while no particles or significant NOx were detected in Mode 3 throughout the process. The quantitative NH4NO3 yield was significantly influenced by discharge power and NH3 flow rate, reaching its highest value in Mode 1 at 24 W and 20 sccm in this investigation. Directly mixing the air discharge products with NH3 in Mode 1 under the threshold decomposition temperature of NH4NO3 leads to the stable formation of NH4NO3. Discharging in the NH3/air mixture will inhibit the generation of NOx and further restrain the NH4NO3 formation in Mode 2 and 3. Additionally, the temperature rises during discharge and also decomposes NH4NO3, resulting in unstable NH4NO3 formation in Mode 2.