Study on the chemical adsorption of gaseous As2O3 by ash.

• Thermal stability analysis of As clarifies dominance of chemical adsorption. • As amount adsorbed by ash in flue gas is far less than ash's adsorption capacity. • Chemical adsorption by ash is mainly through the joint action of Ca and Fe in ash. • As Adsorption by high-Ca ash increases with temperature due to the stable product. • Instability of Fe 2 O 3 product make As amount adsorbed by high-Fe ash peak at 800 °C. Arsenic (As) transformation during flue-gas cooling process determines terminal As emission. In this study, the dominant role of chemical adsorption in gaseous As transformed to ash was confirmed. Dynamic curves of As 2 O 3 adsorption by ash at 500–900 °C were obtained. The adsorbed As amount increased linearly with time, far from reaching saturation, and the maximum amount was approximately 10 times the As content in ash collected from power plant dust collectors, indicating that the actual capacity of ash was far higher. Analysis of As form and elemental distribution directly proved that chemical adsorption by ash was mainly through the joint action of Ca and Fe, and its correlation with other components was weak. At 500–900 °C, as temperature increased, the amount of As adsorbed by CaO gradually increased, whereas that of Fe 2 O 3 first increased and then decreased. The adsorption product of CaO was stable, whereas certain forms of products of Fe 2 O 3 released at 800 °C. Therefore, as temperature increased, the amount of As adsorbed by ash with high Fe content first increased and then decreased, reaching a maximum at 800 °C °C, whereas that of ash with higher Ca content kept increasing. The strong adsorption capacity of ash with high Ca and Fe contents helps reduce terminal As emission. [ABSTRACT FROM AUTHOR]