Abstract
Sulfite and heavy metals are crucial pollutants in the slurry produced by flue gas desulfurization. In this study, a novel cobalt-based activated carbon fiber (Co-ACFs) catalyst-adsorbent was synthesized using an impregnation method; this bifunctional catalyst-adsorbent was used in wet magnesia desulfurization for the simultaneous catalytic oxidation of magnesium sulfite and uptake of heavy metal (Hg2+, Cd2+, and Ni2+) ions. The morphology and surface chemistry of ACFs before and after cobalt loading were investigated using various characterization methods. The kinetics on catalytic oxidation of magnesium sulfite was investigated, and the effects of operation conditions on the simultaneous adsorption capacity of heavy metals were examined. Relative to a non-catalysis material, the 40% Co-ACFs material increased the oxidation rate of magnesium sulfite by more than five times. The Langmuir model can describe the adsorption behavior of Co-ACFs on Hg2+, Cd2+, and Ni2+, indicating that the simultaneous uptake of heavy metals is a single-layer adsorption process. The maximum adsorption capacities for Hg2+, Cd2+, and Ni2+ are 333.3, 500, and 52.6 mg/g, respectively. A pseudo-second-order model confirmed that the removal of heavy metals is controlled by the chemisorption process.
Highlights
Flue gas from coal-fired furnaces is a crucial cause of acid rain, haze, and other pollution-related phenomena
The surface of the Co-activated carbon fiber (ACF) become relatively rough after the introduction of cobalt species
transmission electron microscopy with energy dispersive spectrometer (TEM-EDS) characterization was further conducted to investigate the existence of cobalt oxide particles and the cobalt content in Co-ACFs
Summary
Flue gas from coal-fired furnaces is a crucial cause of acid rain, haze, and other pollution-related phenomena. The composition of this gas is complex because it contains various pollutants such as dust, SO2 , NOx , and heavy metals; pollutants have caused serious harm to the atmospheric environment in China [1,2,3,4]. MgO flue gas desulfurization features high desulfurization efficiency, low energy consumption, less investment requirement, and reliable operation; it satisfies the ultra-low emission requirements of industrial boilers under fluctuating flue gas conditions. To prevent the crystallization of magnesium sulfate in the absorption tower in a traditional magnesia desulfurization process, the concentration of magnesium sulfate in the desulfurization solution should be controlled below 10%.
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