Performance of Sorbent Particles for Removal of Cadmium in Hot Gas

Abstract

The use of particulate kaolinite as a sorbent for capturing cadmium compounds in hot flue gas was studied in the influence of temperature and residence time on removal efficiency. More than a half of the cadmium fed into the reactor was captured by kaolinite samples. It was also found that the amount of cadmium captured increased with time and that the removal efficiency at a temperature of 1073K was slightly higher than at 873K. To clarify the mechanism of cadmium adsorption, the solubility of cadmium captured by particulate kaolinite was examined in both water and nitric acid. Acid-soluble cadmium constituted more than 80% of the total captured cadmium, while water-soluble cadmium constituted between 40-80%. This suggests that cadmium does not penetrate into the kaolinite particles, but it remains on the surface and that physical condensation accounts for approximately half of the cadmium aerosol captured by kaolinite particles.