Simultaneous Absorption and Oxidation of Nitric Oxide and Sulfur Dioxide by Aqueous Solutions of Sodium Persulfate Activated by Temperature

The absorption–oxidation of nitrogen oxide (NO) induced by aqueous solutions of sodium persulfate (Na 2 S 2 O 8 ) in the presence of SO 2 has been studied in a bubble column reactor operated in semibatch mode. The effects of Na 2 S 2 O 8 concentration (0.01–0.20 M), temperature (23–70 °C), 1550 ppm gas-phase SO 2, and solution pH on NO removal (1000 ppm gas-phase concentration) were investigated. The presence of SO 2 dramatically improved NO gas absorption and oxidation while it was itself completely removed. The NO fractional conversions in the presence of SO 2 ranged from 77% to 83%, with the greatest effect occurring at lower temperatures (23 and 30 °C). While persulfate concentration of 0.1 M appeared optimal for aqueous NO removal, both in the absence and presence of SO 2, significant improvements in NO removal were observed for persulfate concentrations of >0.05 M but antagonistic effects were observed with concentrations of <0.05 M in the presence of SO 2, compared to without SO 2 . The pH range of 6.5–8.5 appears to be ideal for NO removal in the presence of SO 2 . The individual and simultaneous chemistry of NO x and SO 2 removal by persulfate is discussed. The results demonstrate the feasibility of removing NO x and SO x simultaneously by aqueous scrubbing.