Removal of NO and NOx using electrochemically generated Ag(II)/Ag(I) redox mediator in nitric acid medium

摘要

The objective of this work was to develop a process for removal and treatment of waste industrial exhaust gases like NO and NO2 by a mediated electrochemical oxidation (MEO) process-based wet scrubbing method. The electrochemically generated Ag(I)/Ag(II) redox mediator system in nitric acid medium was circulated continuously through a packed-bed column by a closed loop, and the NOx was oxidatively removed by absorption/oxidation. Numerous experimental runs were carried out in order to observe the performance of the wet scrubber-electrochemical cell integrated system as a function of the operating conditions: the initial NO concentration in the feed (400-1200 ppm), superficial gas velocity (0.121-0.364 m/s), concentration of Ag(I) ion mediator (0.01-0.1 M), and the temperature (15-45℃). Low initial NO feed, low gas velocities and high Ag(I) concentration were most suitable for high removal performance. Optimization studies were also carried for the above parameters with complete removal of NO and NOx. 93.5% removal of NO and 73.3% removal of NOx were achieved in the oxidation with electrogenerated Ag(II) in a single stage gas scrubber at 25℃ and atmospheric pressure. This Ag(I)/Ag(II) redox mediator system can be regenerated continuously during the process.