As2O3 capture from incineration flue gas by Fe2O3-modified porous carbon: Experimental and DFT insights

Abstract

A series of Fe2O3-modified porous carbon sorbents (Fe/PC) were synthesized and used for As2O3 capture from incineration flue gas. The molecular interaction mechanism was investigated by theoretical calculations based on density functional theory (DFT). The results indicate that the flourishing pore structure and high specific surface area of porous carbon are beneficial for Fe2O3 dispersing, which provides affluent active sites for arsenic capture. Fe/PC sorbent with a Fe content of 14.93 wt% exhibited high arsenic removal capacity of 16.09–29.32 mg/g in a wide temperature window (150–400 °C). The pseudo-first-order model best fitted the experimental data of As2O3 removal. The influences of flue gas compositions depend on the adsorption temperature. H2O promoted arsenic removal at lower temperature. HCl and SO2 played facilitation roles in arsenic removal at higher temperature. The states of arsenic in sorbents were As3+ and As5+, both adsorption and oxidation processes are responsible for As2O3 removal by Fe/PC sorbents. DFT calculation results indicate that the O-hollow site on the Fe2O3 surface has the strongest adsorption affinity for As2O3. The deep orbital hybridization and electron sharing between As2O3 and Fe2O3 are responsible for the high adsorption performance of Fe/PC sorbent.