The addition of Fe2O3 into furnaces is a promising method for arsenic pollution control. Nevertheless, Fe2O3 particles undergo serious sintering under actual furnace temperatures. To improve its sintering resistance, Fe2O3 hollow microspheres were synthesized by the template method and were tested in flue gas containing SO2 and NO in the range of 1000-1300 °C. The results demonstrated that the amount of arsenic captured could be steadily maintained above 5 mg/g throughout the operating temperature range, and Fe2O3 microspheres could maintain the originally developed pore structure and hollow morphology well even at 1200 °C. Based on product analysis and density functional theory calculations, the fixation pathway of arsenic was proposed. In no oxygen conditions, As2O3 was first bound to the Fe2O3 surface by forming an -O-As-O-Fe stable structure and then was oxidized by lattice oxygen. The introduction of O2 could regenerate the consumed lattice oxygen and therefore promote arsenic capture. Finally, the oxidized arsenic was fixed in products in the form of FeAsO4. Additionally, the impact of acid gases was also investigated. SO2 showed a notable inhibiting effect on arsenic capture, while the impact of NO was less noticeable.
Keywords: arsenic adsorption; coal-fired flue gas; hollow microspheres; iron oxide; particle sintering.