Catalytic Oxidation Removal of Sulfur Dioxide by Ozone in the Presence of Metallic Ions

Abstract

Desulfurization of flue gas by ozonation aided by the catalysis of a metallic ion was investigated experimentally. The results showed that the removal efficiency of SO 2 was only 30% at a 1:1 molar ratio of O 3 /SO 2 without the addition of a catalyst. However, the efficiency was substantially increased when a metallic ion was added to the absorption solution at the same ratio of O 3 /SO 2 . In particular, the performance was optimal using a Mn 2+ catalyst. Under the optimal condition given as the absorption liquid temperature of 20 °C, gas flow rate of 10 L/min, molar ratio of 1.0 for O 3 /SO 2 , and Mn 2+ concentration of 6.4 × 10 −4 mol/L, the removal efficiency of SO 2 was 99%. A reaction mechanism of SO 2 with ozone in the liquid-phase oxidation catalyzed by Mn 2+ was proposed. The advantage of ozonation desulfurization technology is that SO 2 is directly transformed into a valuable product, sulfuric acid, which provides favorable environmental and economic benefit.

Simultaneous Sulfite Electrolysis and Hydrogen Production Using Ni Foam-Based Three-Dimensional Electrodes

“…East Asia is the most threatened region by anthropogenic SO 2 emissions because of China’s high dependence on coal. , To mitigate the current situation, flue gas desulfurization (FGD) technologies have been implemented in order to capture SO 2 from gas streams in power plants . In particular, wet-type technologies with high removal efficiencies are preferred, in which SO 2 becomes sulfite (SO 3 2– ). , Then, by exposing the resulting solution to strong oxidants, such as ozone, disposals can be transformed into useful byproducts . Notably, the use of aqueous ammonia as an absorbent with subsequent oxidation yields ammonium sulfate, which has potential use as a fertilizer …”

Theoretical study of the oxidation reactions of sulfurous acid/sulfite with ozone to produce sulfuric acid/sulfate with atmospheric implications

“…4,[13][14][15] The oxidation reactions of SO 2 have been extensively studied in a variety of experimental approaches and theoretical calculations. 1,[12][13][14][16][17][18][19][20][21][22][23][24][25][26][27] Several reaction mechanisms have been proposed, ranging from gas-phase oxidation by atmospheric radicals (Criegee intermediate 16,17,[25][26][27] and hydroxyl 4,13,14 and hydroperoxy radicals 18 ) to aqueous-phase reaction by O 3 , 20,24,28 hydrogen peroxide, 29 and others. 30 To date, a consensus has emerged that the production of gaseous sulfate is determined by the SO 2 + OH reaction.…”

“…New models have been recently proposed for the formation of sulfate in the troposphere, clouds, aerosols, acid rain, and fog to bridge the gap between the modeled and observed sulfate. 20,[32][33][34][35] SO 2 can be quickly taken into fog and rain droplets, 36 which is followed by its liquid phase oxidation by O 3 and H 2 O 2 . 20,24,28,29,37,38 Model studies suggest that the oxidation of SO 2 in the aqueous phase results in more than 80% of the global sulfate production.…”

“…20,[32][33][34][35] SO 2 can be quickly taken into fog and rain droplets, 36 which is followed by its liquid phase oxidation by O 3 and H 2 O 2 . 20,24,28,29,37,38 Model studies suggest that the oxidation of SO 2 in the aqueous phase results in more than 80% of the global sulfate production. 39 In some of these models, the hydrolysis reaction of SO 2 plays an important role, and bisulte anion (HSO 3 À ) serves as a product of hydrolysis, which is one of the dominant sulfur(IV) species.…”

“…24) together with transition metal ion catalysts (Co 2+ , Fe 3+ , and Mn 2+ ). 20,40 Furthermore, the gas-phase oxidation of SO 2 by O 3 is known to have minor contributions to atmospheric sulfate formation due to its relatively high energy barrier and small rate constant. 49 However, Cheng et al have reported that the concentrations of O 3 drop dramatically during the haze period together with an increase in sulfate production; this suggests new possible pathways for the formation of sulfate in the presence of O 3 .…”