Adsorption and reaction mechanism of arsenic vapors over γ-AlO in the simulated flue gas containing acid gases.

Arsenic emission from fuel combustion and metal smelting flue gas causes serious pollution. Addition of sorbents is a promising way for the arsenic capture from high temperature flue gas. However, it is difficult to remove arsenic from SO/HCl-rich flue gas due to the competitive reaction of the sorbents with arsenic and these acid gases. To solve this problem, arsenic adsorption over γ-AlO was studied in this work to evaluate its adsorption mechanism, resistance to acid gases as well as regeneration behavior. The results show that γ-AlO had good resistance to acid gases and the arsenic adsorption by γ-AlO could be effectively carried out at a wide temperature range between 573 and 1023 K. Nevertheless, adsorption at higher-temperature (like 1173 K) leaded to the decrease of surface area and the rearrangement of crystal structure of γ-AlO, reducing the active sites for arsenic adsorption. The adsorption of arsenic was confirmed to occur at different active sites in γ-AlO by forming various adsorbed species. Increasing temperature facilitated arsenic transformation into more stable chemisorbed As and As which were difficult to remove through thermal treatment regeneration. Fortunately, the regeneration of spent γ-AlO could be well performed using NaOH solution.