Nitrate and nitrite fertilizer production from air and water by continuous flow liquid-phase plasma discharge

Abstract

The current nitrogen production technology requires a large amount of fossil fuel based H2, which is unsustainable and results in profound environmental consequences. In this study, a novel, continuous flow liquid-phase plasma discharge (CFLPPD) reactor was investigated to produce nitrate and nitrite in liquid as nitrogen fertilizer. Three CFLPPD operating parameters were examined including air flow rate, power applied, and treatment time, all at three levels (0.5, 1.25, 2.0 L/min for air flow rate; 100, 200, and 300 W for power applied; and 20, 40, and 60 min for treatment time) using a 3 × 3 × 3 factorial design. The results showed that the production of NO3 and NO2 (NOx) increased linearly with increasing power usage under all tested air flow rates. The highest yields of NOx under three treatment times were associated with an air flow rate of 2.0 L/min and power usage of 300 W, which were 73.0, 110.8, and 136.2 mg/L, respectively. The best energy efficiency of 1.108 g-NOx/kWh was obtained corresponding to the operating condition of 2.0 L/min in air flow rate, 300 W in power usage, and 40 min in treatment time. The concentration of H2O2 was linearly correlated with the NOx concentration in the CFLPPD treated liquid (R = 0.9747). The liquid pH rose slightly ranging from 7.79 to 8.79, which was not detrimental to the nutrients uptake by the crops receiving the NOx fertilizer produced in this study. The work presented a green technique to manufacture nitrogen fertilizer for sustainable crop production.