Simultaneous NO and SO2 removal by aqueous persulfate activated by combined heat and Fe2+: experimental and kinetic mass transfer model studies.

This study evaluates the chemistry, kinetics, and mass transfer aspects of the removal of NO and SO2 simultaneously from flue gas induced by the combined heat and Fe2+ activation of aqueous persulfate. The work involves experimental studies and the development of a mathematical model utilizing a comprehensive reaction scheme for detailed process evaluation, and to validate the results of an experimental study at 30-70 °C, which demonstrated that both SO2 and Fe2+ improved NO removal, while the SO2 is almost completely removed. The model was used to correlate experimental data, predict reaction species and nitrogen-sulfur (N-S) product concentrations, to obtain new kinetic data, and to estimate mass transfer coefficient (KLa) for NO and SO2 at different temperatures. The model percent conversion results appear to fit the data remarkably well for both NO and SO2 in the temperature range of 30-70 °C. The conversions ranged from 43.2 to 76.5% and 98.9 to 98.1% for NO and SO2, respectively, in the 30-70 °C range. The model predictions at the higher temperature of 90 °C were 90.0 and 97.4% for NO and SO2, respectively. The model also predicted decrease in KLa for SO2 of 1.097 × 10-4 to 8.88 × 10-5 s-1 (30-90 °C) and decrease in KLa for NO of 4.79 × 10-2 to 3.67 × 10-2 s-1 (30-50 °C) but increase of 4.36 × 10-2 to 4.90 × 10-2 s-1 at higher temperatures (70-90 °C). This emerging sulfate-radical-based process could be applied to the treatment of flue gases from combustion sources. Graphical abstract.