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The simultaneous control of SO2/NOX can be realized with the [Fe(II)‐EDTA]2− aqueous solution. However, the [Fe(II)‐EDTA]2− is easily oxidized to [Fe(III)‐EDTA] − by oxygen, which has no ability to bind NO. The reduction of [Fe(III)‐EDTA] − to [Fe(II)‐EDTA]2− is a key to the maintenance of the NO removal efficiency with the [Fe(II)‐EDTA]2− aqueous solution. The reduction of [Fe(III)‐EDTA]− can be accomplished by sulfite produced by SO2 dissolving in the aqueous solution under the catalysis of activated carbon. The experiments were performed in a fixed‐bed reactor to investigate the regeneration of [Fe(II)‐EDTA]2− catalyzed by activated carbon. The influences of [Fe(III)‐EDTA] − and sulfite concentrations, pH, liquid flow, temperature, on [Fe(III)‐EDTA] − catalytic reduction have been tested. The experimental results indicate that the [Fe(III)‐EDTA]− reduction increases with the [Fe(III)‐EDTA]− and sulfite concentrations. Raising the temperature can increase the [Fe(III)‐EDTA] − conversion. The optimal pH range for the reduction of [Fe(III)‐EDTA] − is 5.7–7.5. The apparent activation energy determined from the experimental results is 35.2 ± 0.5 kJ mol−1. The continuous experiment manifests that simultaneous removal of NO and SO2 with the [Fe(II)‐EDTA]2− solution coupled with the Fe(II) regeneration catalyzed by activated carbon can be maintained at a high NO removal efficiency for a long period of time. The kinetic equation of [Fe(III)‐EDTA]‐ reduction by sulfite catalyzed with activated carbon can be described as r = k 2 k 1 KC[Fe(III)−EDTA]−1/n C H + C SO32− k − 1 C EDTA true( 1 + C normalH + / Knormalaθ true) + k 2 C SO32− · ρ b ε © 2012 American Institute of Chemical Engineers Environ Prog, 32: 206‐212, 2013

The wet ammonia (NH 3 ) desulfurization process can be retrofitted to remove nitric oxide (NO) and sulfur dioxide (SO 2 ) simultaneously by adding soluble cobalt(II) salt into the aqueous ammonia solution. Activated carbon is used as a catalyst to regenerate hexaminecobalt(II), Co(NH 3 ) 6 2þ , so that NO removal efficiency can be maintained at a high level for a long time. In this study, the catalytic performance of pitch-based spherical activated carbon (PBSAC) in the simultaneous removal of NO and SO 2 with this wet ammonia scrubbing process has been studied systematically.

A novel method has been put forward to retrofit the wet ammonia desulfurization process to realize the combined removal of sulfur dioxide and nitric oxide by introducing soluble cobalt(II) salt into aqueous ammonia solution. The active constituent of scrubbing NO from the flue gases is the CoðNH 3 Þ 2þ 6 produced by ammonia coordinating with Co 2þ . The regeneration of CoðNH 3 Þ 2þ 6can be realized under the catalysis of activated carbon so as to sustain a high NO removal efficiency for a long time. In this paper, the adsorption-reduction behavior of CoðNH 3 Þ 3þ 6 on activated carbon has been researched using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. A conclusion can be drawn from the results that cobalt ions in the aqueous solution are adsorbed by activated carbon and most of them are reduced to Co 2þ ions, and some of the Co 2þ ions are further reduced into metallic cobalt. The results also demonstrate that the functional groups on the surface of carbon take part in this redox reaction. The C-H groups on the carbon surface are oxidized into C-OH, and then some of the hydroxyl groups are further oxidized into carbonyl or carboxyl groups.