Simultaneous NO and SO 2 removal by aqueous persulfate activated by combined heat and Fe 2+ : experimental and kinetic mass transfer model studies

Abstract

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 (K_La) 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 K_La for SO₂ of 1.097 × 10⁻⁴ to 8.88 × 10⁻⁵ s⁻¹ (30–90 °C) and decrease in K_La 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

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