Review on Magnetic Adsorbents for Removal of Elemental Mercury from Flue Gas

Abstract

Mercury in flue gas has been identified to be one of the most harmful environmental pollutants to humans and other organisms as a result of its bioaccumulation, volatility, persistence, high toxicity, etc. Although many adsorption removal technologies have been developed to control mercury emissions, they are difficult to be used in practical industrial applications as a result of their own technology and cost constraints. Thus, more efficient and low-cost mercury pollution control technologies need to be further developed. Because of its good adsorption performance, easy separation and recovery, low toxicity, and high chemical stability, magnetic adsorbents are considered as one of the most promising adsorbents for controlling mercury emissions in flue gas. This review mainly analyzes the latest developments and research progress in the removal of Hg 0 in flue gas by magnetic adsorbents, especially magnetic iron-based adsorbents, magnetic carbon-based adsorbents, magnetic fly-ash-based adsorbents, and magnetic mineral-based adsorbents. The Hg 0 removal performance, mechanism, and kinetics of magnetic adsorbents are reviewed. The effects of flue gas compositions (such as O 2 , NO, SO 2 , CO 2 , H 2 O, etc.) on Hg 0 capture performance are summarized. The merits and drawbacks of magnetic adsorbents for capturing Hg 0 and the future development directions are also discussed. In comparison to other adsorbents, magnetic adsorbents can be easily separated from fly ash as a result of their better magnetization characteristics. It was found that the MoSe x (inter)Fe 3 O 4 adsorbent showed good Hg 0 removal performance, and the capacity of Hg 0 removal was up to 135 mg/g. In addition, considering the entire life cycle, magnetic adsorbents are more attractive in costs than other common adsorbents. The development and design of the magnetic adsorbents, which possess high adsorption efficiency, simple and efficient separability, green sustainability, good regeneration ability, and low production cost, are considered to be one of the research hotspots in the future. The purpose of this work is to provide theoretical guidance for the further development of magnetic adsorbents in the field of mercury control.

Removal of CO2 from Flue Gas Using Seaweed Porous Carbons Prepared by Urea Doping and KOH Activation

“…The CO 2 adsorption capacity of NSK (2) decreases from 4.06 to 3.31 mmol/g, and the CO 2 adsorption capacity of NEK (2) decreases from 3.25 to 2.83 mmol/g. This may be because the H 2 O (g) will condense and form a water film on the surface of adsorbents, thereby blocking the pores. − Another possible reason is that H 2 O (g) may compete with CO 2 to adsorb at the active sites on the adsorbent surface, thereby reducing the adsorption performance of CO 2 . − The research of Chen et al also found that the adsorption capacity of CO 2 decreased correspondingly with the increase of water molecules.…”

Removal of Elemental Mercury Using Seaweed Biomass-Based Porous Carbons Prepared from Microwave Activation and H2O2 Modification

“…Then, these formed new active substances can further participate in the process of Hg 0 removal, thus being able to increase the Hg 0 capture efficiency. The specific reaction steps are described by eqs –. − …”

Mercury Removal from Flue Gas by Noncarbon Sorbents

“…The Ag nanoparticles tended to grow to larger and nonuniform particles, which will decrease the Hg 0 removal performance of Ag/ zeolite. 34 Several effective strategies for controlling the size and 19…”