Enhanced selective production of nitrate in a gas–liquid phase dielectric barrier discharge reactor

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Abstract
A dual-chamber gas–liquid phase dielectric barrier discharge (DBD) reactor with tri-electrodes was designed for air-fed nitrogen fixation (NF). Air was activated in the gas-phase discharge chamber to produce nitrogen oxides (NO x ), and these NO x species continued to synthesize aqueous nitrate species in the gas–liquid discharge chamber. The effect of electrode configuration, applied voltage, air flow rate, initial solution pH and electric discharge duration on the concentration, selectivity of nitrate/nitrite/ammonia, total nitrogen concentration and energy yield (EY) of NF was studied. The results showed that the DBD reactor with tri-electrodes efficiently produced microdischarges for N 2 fixation with high nitrate selectivity at a higher applied voltage. The initial pH of the water in the lower discharge chamber had little effect on the input power but a significant impact on the transfer and conversion of gaseous NO x into aqueous nitrate, and a weak alkaline pH was more favorable for total nitrogen accumulation. Meanwhile, the input air flow rate in the DBD reactor and the water volume in the lower discharge chamber showed an optimum value, and the EY of total NF reached a maximum of 0.84 g kWh −1 at an initial solution pH 11 and water volume of 35 ml. The optical emission spectrum in the discharge regions indicated that the NF results at different applied voltages and air flow rates can be attributed to their influence on the production of N 2 * , N 2 + and •OH, and the experiments including electron quenching and dry air discharge indicated that NH 4 + was mainly produced via the reduction of N 2 by hydrated electrons.
Funding Information
  • National Natural Science Foundation of China (21577011)

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