Deep insight into the effect of NaCl/HCl/SO2/CO2 in simulated flue gas on gas-phase arsenic adsorption over mineral oxide sorbents

Coal combustion is one of the major pathways by which arsenic enters the ecological environment. An effective method to control arsenic emissions in-furnace is to transform the arsenic from a vapour to fly ash particles using mineral sorbents. However, flue gas components have a significant effect on gas-phase arsenic adsorption, which limits the industrial application of mineral sorbents. In this paper, the effect mechanism of flue gas components (NaCl/HCl/SO2/CO2) on gas-phase arsenic adsorption over different mineral oxide sorbents was investigated. The results demonstrate that the order of arsenic adsorption is CaO > MgO/Fe2O3> NaCl > Al2O3 > SiO2. NaCl promotes the arsenic adsorption of CaO above 800 degrees C, and the arsenic removal efficiency of CaO with 5 % NaCl is 52.51 % at 900 degrees C. NaCl inhibits the arsenic adsorption of MgO and Fe2O3, and promotes arsenic adsorption by Al2O3 and SiO2. Acid gases inhibit arsenic adsorption by the sorbents and the order of the inhibition intensity of acid gases at 700 degrees C is HCl > SO2 > CO2. The active sites (Ca-O, FeO, or AlO bonds) in the sorbents are the main reaction sites for arsenic adsorption, and captured arsenic is in the form of AsO-1/2- and AsO3/4.

Automated summary

The study found that different mineral oxide sorbents have varying effects on gas-phase arsenic adsorption, with NaCl promoting or inhibiting the arsenic adsorption efficiency of different sorbents. Acid gases also have different inhibitory effects on the adsorption, with the order of inhibition intensity being HCl > SO2 > CO2 at 700 degrees C.