An improved method of removal for high concentrations of NO by electro-scrubbing process

In the Ag(II)/Ag(I) redox mediator integrated scrubber system, NO reacts with the Ag(II) ions produced by the electrochemical oxidation of Ag(I) in an electrochemical cell present in the scrubbing solution (aqueous HNO3 acid) to form NO2. This NO2 is then absorbed into the scrubbing solution and degraded to nitrate. Numerous experimental runs were carried out to evaluate the feasibility of the integrated system to treat industrial waste gases containing high NOx levels. The results showed that the levels of NO and NOx removal increased with increasing Ag(II) loading and contact time. Under optimized conditions, 93.5% and 73.3% of the NO and NOx, respectively, were removed by a single stage gas scrubber with 1.62 g L−1 Ag(II) operating at 25 °C and atmospheric pressure.

► Ag(II) produced by the electrochemical oxidation is as a strong oxidant.
► High loading NO reacts with the Ag(II) to form NO2.
► NO2 is absorbed into the scrubbing solution and degraded to nitrate.
► Low level of Ag(II) shows higher efficiencies for NO and NOx removal at 25 °C.