Fabrication of Al2O3/CaO with anti-sintering for efficient removal of As2O3 in simulated flue gas: Experimental and DFT study

Calcium oxide (CaO), as a high temperature sorbent, has been widely applied in the field of heavy metal removal due to its low price and stable chemical properties, but CaO tends to sinter at high temperature, which affects the adsorption performance. In this work, Al 2 O 3 /CaO sorbent with resistance to sintering was synthesized via citric acid and calcine method, which was innovatively employed to the adsorption of As 2 O 3 combining experiment and theoretical analysis. The experimental results demonstrate that the adsorption capacity of untreated CaO reduces immensely with the temperature rising from 1073 to 1273 K, and arsenic adsorption capacity reduces from 303 to 50 mg/kg. Whereas, arsenic adsorption capacity of Al 2 O 3 /CaO almost maintains at high level and reaches to 534 mg/kg at 1173 K, which proves that the addition of Al 2 O 3 can improve the anti-sintering ability of CaO. Meanwhile, through density functional theory (DFT), the adsorption sites of Al 2 O 3 /CaO was further studied. Al site of Al 2 O 3 /CaO was found to be the main adsorption active site and electron transfer channel, which effectively facilitates the separation of lattice oxygen. Finally, the adsorption mechanism of As 2 O 3 on Al 2 O 3 /CaO was proposed.