Novel process for simultaneous removal of NO(x) and SO2 from simulated flue gas by using a sustainable Ag(I)/Ag(II) redox mediator.

The objective of this work is to develop a sustainable process for simultaneous removal of waste gases such as NO, NO2, and SO2 by an electrochemically generated Ag(I)/Ag(II) redox mediator system. High removal efficiency was achieved for NO and SO2 by the wet scrubbing method at room temperature and atmospheric pressure. This removal is achieved through oxidation and absorption by contacting the gaseous stream with redox mediator ions that offer specific or selective solubility for the solute gases to be recovered in a wet scrubber. The process parameters such as gas velocity, liquid velocity, Ag(I) concentration, and HNO3 concentration were investigated to explore the possibility of complete removal of waste gases. The Ag(I)/Ag(II)-based mediated electrochemical oxidation process proved to be quite effective for simultaneous removal of NO, NO(x), and SO2 from the simulated flue gas mixtures containing NO and SO2 over a wide concentration range of 100-400 ppm. Studies were carried out with individual gas components for the mixture, and the effect of input NO and input SO2 concentrations on the NO(x) and SO2 removal efficiencies at 20 degrees C was examined. Complete oxidation of NO to NO2 with 100% NO removal efficiency and 92% NO(x) removal efficiency was achieved along with 100% SO2 removal efficiency, highlighting a potentially far greater efficiency of the Ag(I)/Ag(II)-based system in functionality and selectivity. Active research work in this direction is anticipated in the near future.