Absorption and oxidation of nitric oxide (NO) by aqueous solutions of sodium persulfate in a bubble column reactor

The absorption-oxidation of nitric oxide (NO) by aqueous solution of sodium persulfate (Na₂S₂O₈) has been studied in a bubble column reactor operated in semibatch mode. The effects of different process variables such as the persulfate concentration (0.01-0.2 M), temperature (23-90 °C), pH (4-12), sodium chloride concentration (0-0.5 M), and NO concentration (500-1000 ppm) were studied. In general, the NO fractional conversion (percent of inlet NO removed) at all temperatures increased almost linearly with persulfate concentration up to about 0.1 M, after which it started to level off. Increased temperature led to an increased fractional conversion of NO at all persulfate levels. At 0.1 M persulfate concentration, conversions of up to 69% and 92% were observed at 70 and 90 °C, respectively. Solution pH and chloride concentration were both found to affect NO absorption at higher temperatures. The effect of pH was moderate, but sodium chloride showed a significant effect on NO absorption at 70 °C, to the point of causing complete removal of NO. The effect of initial NO concentration in the gas phase was found to be marginal. The results demonstrate the feasibility of NO removal using aqueous solutions of sodium persulfate.