Suppressing Ammonia Re-Emission with the Aid of the Co₃O₄-NPs@KIT-6 Catalyst in Ammonia-Based Desulfurization

Abstract

The re-emission of NH3 and SO2 caused by the decomposition of (NH4)2SO3 is a crucial concern in ammonia-based desulfurization. In this study, a novel Co3O4-NPs@KIT-6 catalyst with a three-dimensional two-helix structure is proposed for converting (NH4)2SO3 into (NH4)2SO4. The oxidation rate of (NH4)2SO3 with the catalyst was 7.5 times that without any catalyst, and this improvement was attributed to appropriately dispersed Co3O4 nanoparticles with a size of 4–10 nm that interacted with the KIT-6 support. Therefore, the number of active sites with substitution and hole defects was substantially increased, which is advantageous for high catalytic activities. Consequently, the amount of NH3 and SO2 re-emission during (NH4)2SO3 oxidation was reduced by 43.9%, which considerably reduced potential environmental risks. The results of this study serve to advance ammonia desulfurization by improving the desulfurization efficiency, downsizing the oxidation tank, and generating considerable profit from efficient reclaiming of (NH4)2SO4 as a fertilizer.

Oxygen-vacancy enhanced CoO/CeO2 heterojunction for synchronous regulation of sulfur resourcing and selenium adsorption separation from flue gas desulfurization wastewater

“…The turnover frequencies (TOF) of catalysts for SO 3 2− oxidation were calculated according to ESI Text S4 †. OV-CoO/CeO 2 had the highest catalytic oxidation rate and a high turnover frequency compared with other catalysts (Mn@ZIF67, 68 Co/C 3 N 4 , 17 Co-MOF-74, 18 Co 3 O 4 -NPs@KIT-6, 10 BISC, 14 and Co-MCM-48 (ref. 19)) owing to the abundance of OVs, high amount of Co, and increased O* transfer.…”

“…To accelerate SO 3 2− oxidation, multiple catalytic methods have been developed, such as homogeneous catalysis, 7–9 heterogeneous catalysis, 10–12 and photocatalysis. 13 Heterogeneous catalysis is the most suitable method owing to its efficiency, practicality, and secondary environmental impact.…”

“…14–16 In previous studies, we fabricated a series of Co-based monometallic catalysts, including Co/C 3 N 4 , Co-MOF-74, Co 3 O 4 -NPs@KIT-6, BISC, and Co-MCM-48, with SO 3 2− oxidation rates 3–10 times higher than that without a catalyst. 10,14,17–19 Owing to their high catalytic activity, recyclability, and low secondary pollution, Co-based catalysts have great potential for use under real WFGD operating conditions. According to the steady-state assumption 20 and DFT calculations, 14 oxygen diffusion and mass transfer on the heterogeneous catalyst are crucial in SO 3 2− oxidation and determine the overall reaction rate.…”

Ammonium Sulfite Slurry from Ammonia-Based Desulfurization Activates Water-Soluble Humic Substances from Lignite: Performance, Application, and Mechanism

“…3 Due to its high concentration, however, (NH 4 ) 2 SO 3 in the ammonium sulfite slurry (ASS) is not conducive to be oxidized, which not only results in the low oxidization efficiency but also the re-emission of NH 3 and SO 2 . 4 Moreover, the production of ammonium sulfate from ASS often requires energy intensive processes including evaporation, crystallization, solid−liquid separation, desiccation, and so on. Therefore, enhancing the utilization efficiency and simplifying the reuse process of ASS byproducts are extremely crucial.…”

“…During the ammonia-based desulfurization, the SO 2 is converted into sulfite (SO 3 2– ) in solution, which is exposed to a large amount of air for the oxidation reaction and yields ammonium sulfate as a potential fertilizer . Due to its high concentration, however, (NH 4 ) 2 SO 3 in the ammonium sulfite slurry (ASS) is not conducive to be oxidized, which not only results in the low oxidization efficiency but also the re-emission of NH 3 and SO 2 . Moreover, the production of ammonium sulfate from ASS often requires energy intensive processes including evaporation, crystallization, solid–liquid separation, desiccation, and so on.…”