Integrated As2O3/SeO2 capture mechanism by Mn–Fe binary oxide in coal-fired flue gas

The integrated capture of multiple pollutants is a prospective approach to achieve the economical pollution reduction. In this work, the integrated capture of As2O3 and SeO2 in coal-fired flue gas by Mn–Fe binary oxide was investigated combined the experiments and density functional theory (DFT) calculations. Results showed that Mn–Fe binary oxide has a significant performance for As2O3 and SeO2 removal. When the Mn/Fe ratio was 1:1, Mn–Fe binary oxide presented the optimum capture ability for As2O3 (SeO2) at 600 °C (750 °C). For the integrated adsorption progress, As2O3 exhibited a better adsorption selectivity than SeO2, which made it easier to adsorb onto sorbent surface, prior to SeO2, and it was negative to SeO2 capture. On the other hand, the presence of SeO2 facilitated the As2O3 capture, for that the pre-adsorption product of SeO2 was favorable to As2O3 retention. Aiming to the phenomenon, DFT calculations were conducted to reveal the integrated adsorption mechanism. Mn and Fe sites were active sites on Fe/Mn3O4 surface for As2O3 and SeO2 adsorption. The presence of SeO2 increased the As2O3 adsorption energy on Fe/Mn3O4 surface, while the adsorption energy of SeO2 decreased with As2O3 introduction. In addition, the adsorption energy of As2O3 on Fe/Mn3O4 surface with pre-adsorbed selenium was higher than that on the clean surface, and it might be reason for the positive effect of pre-adsorbed selenium on As2O3 capture. The results from this work would help to provide an insight on the integrated removal of trace element (TEs) from coal-fired power plant.