Efficient capture of As2O3 in high-temperature flue gas by Fe2O3/CaSiO3 with anti-sintering properties: Experimental and DFT study

A Fe 2 O 3 /CaSiO 3 composite adsorbent was synthesized using calcium nitrate as a precursor for the adsorption and removal of As 2 O 3 from high-temperature flue gas at temperatures ranging from 1073 K to 1273 K. A combination of experimental investigations and theoretical calculations was employed to analyze the impact of Fe-doped calcium silicate on its arsenic adsorption performance, as well as to elucidate the adsorption mechanism of the Fe 2 O 3 /CaSiO 3 composite material for As 2 O 3 . The experimental results demonstrated that the incorporation of Fe 2 O 3 resulted in an enhanced pore structure within the material. When the molar ratio of Fe:Si was set at 1:5, the Fe 2 O 3 /CaSiO 3 adsorbent exhibited optimal As 2 O 3 adsorption capacity at 1273 K, achieving a remarkable value of 996.0 mg/kg—significantly higher than that observed with pure calcium silicate. During the adsorption process, the doped iron oxide released additional free electrons, thereby facilitating the conversion of lattice oxygen into chemisorbed oxygen. Furthermore, density functional theory (DFT) calculations were utilized to further investigate the microscopic mechanisms underlying the behavior of the Fe 2 O 3 /CaSiO 3 composite adsorbent. The findings indicated that Fe sites within Fe 2 O 3 /CaSiO 3 served as primary active sites and electron transport channels for this material, promoting both separation and conversion processes involving lattice oxygen. During arsenic adsorption, significant orbital hybridization occurred between Fe atoms and O atoms in As 2 O 3 , which contributed to enhancing stability within the chemisorption system. Overall, Fe 2 O 3 /CaSiO 3 displayed exceptional performance in terms of arsenic adsorption capabilities along with notable anti-sintering properties, positioning it as a promising composite material for effective arsenic removal under high-temperature conditions.