Abstract
In this study, the manganese-doped manganese–cobalt–iron spinel was prepared by the sol–gel self-combustion method, and its physical and chemical properties were analyzed by XRD (X-ray diffraction analysis), SEM (scanning electron microscope), and VSM (vibrating sample magnetometer). The mercury removal performance of simulated flue gas was tested on a fixed bed experimental device, and the effects of Mn doping amount, fuel addition amount, reaction temperature, and flue gas composition on its mercury removal capacity were studied. The results showed that the best synthesized product was when the doping amount of Mn was the molar ratio of 0.5, and the average mercury removal efficiency was 87.5% within 120 min. Among the fuel rich, stoichiometric ratio, and fuel lean systems, the stoichiometric ratio system is most conductive to product synthesis, and the mercury removal performance of the obtained product was the best. Moreover, the removal ability of Hg0 was enhanced with the increase in temperature in the test temperature range, and both physical and chemical adsorption play key roles in the spinel adsorption of Hg0 in the medium temperature range. The addition of O2 can promote the removal of Hg0 by adsorbent, but the continuous increase after the volume fraction reached 10% had little effect on the removal efficiency of Hg0. While SO2 inhibited the removal of mercury by adsorbent, the higher the volume fraction, the more obvious the inhibition. In addition, in an oxygen-free environment, the addition of a small amount of HCl can promote the removal of mercury by adsorbent, but the addition of more HCl does not have a better promotion effect. Compared with other reported adsorbents, the adsorbent has better mercury removal performance and magnetic properties, and has a strong recycling performance. The removal efficiency of mercury can always be maintained above 85% in five cycles.
Highlights
Mercury, as a highly toxic trace element in nature, has attracted wide attention from environmentalists all over the world due to its volatility and bioaccumulation [1,2,3]
In order to study the influence of temperature on the mercury removal effect of magnetic manganese–cobalt–iron spinel, the temperature of the fixed-bed reactor was set to 100 ◦ C, 125 ◦ C, 150 ◦ C, 175 ◦ C, and 200 ◦ C, and the mercury removal experiment was carried out
A manganese-doped manganese–cobalt–iron spinel adsorbent was prepared by the sol–gel self-combustion method
Summary
As a highly toxic trace element in nature, has attracted wide attention from environmentalists all over the world due to its volatility and bioaccumulation [1,2,3]. These non-carbon-based adsorbents have good mercury removal capacity, they are generally not easy to recycle, while magnetic adsorbents, which are easy to separate from fly ash, can be recycled and reused well, which can significantly reduce the operation cost of power plants. Considering that Co is a natural ferromagnetic element, this study plans to dope manganese ions into cobalt ferrite spinel to prepare a magnetic manganese–cobalt–iron spinel, in order to achieve efficient mercury removal and recyclability of the adsorbent. The adsorption performance of gas-phase zero-valent mercury (Hg0 ) was investigated in a fixed-bed reaction system, and the effects of Mn doping amount, fuel addition amount, reaction temperature, and flue gas components on the mercury removal performance were discussed, and the regeneration performance of the screening of the sorbent was explored, aiming to provide theoretical guidance and research basis for the development of efficient and recyclable spinel ferrite adsorbents
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