Three-layer core-shell magnetic Fe3O4@C@Fe2O3 microparticles as a high-performance sorbent for the capture of gaseous arsenic from SO2-containing flue gas

Abstract Gaseous arsenic capture from flue gas is of great concern due to the high toxicity of arsenic. In this study, a new type of sorbent, magnetic Fe 3 O 4 @C@Fe 2 O 3 microparticles with a core-shell structure, was designed by taking advantages of the easy separation property of magnetic sorbents and the excellent adsorption property of Fe 2 O 3 for the capture of arsenic. The Fe 3 O 4 @C@Fe 2 O 3 material exhibits a three-layer structure with high specific surface area (27.242 m 2  g −1 ), large pore volume (0.181 cm 3  g −1 ) and excellent magnetic properties (74.1 emu g −1 ). The synthesized Fe 3 O 4 @C@Fe 2 O 3 sorbent demonstrates better arsenic capture performance than Fe 3 O 4 , Fe 3 O 4 @C or commercial Fe 2 O 3 materials. The capture rate of Fe 3 O 4 @C@Fe 2 O 3 for gaseous As 2 O 3 could reach 1.94 mg g −1  min −1 in optimal conditions, and its capacity is 36.22 mg g −1 with a breakthrough threshold of 50%. The performance tests indicate that gaseous As 2 O 3 could be efficiently captured from simulated flue gas and that the presence of SO 2 and O 2 plays a crucial role in As 2 O 3 capture. The capture mechanism indicates that the conversion of Fe 3+ /Fe 2+ during the oxidation of SO 2 by O 2 can accelerate the formation of highly active chemisorbed oxygen, and then the adsorbed As 2 O 3 can bond with chemisorbed oxygen to from stable Fe(III)-As(V) compound. After magnetic separation, the spent sorbent can be regenerated through alkali desorption, which facilitates the centralized control of arsenic and the recycling of sorbent. Therefore, the Fe 3 O 4 @C@Fe 2 O 3 composite is a promising sorbent for gaseous As 2 O 3 capture from SO 2 -containing flue gas due to its excellent separation and regeneration properties.