Regeneration of cobalt complexes by thermal decomposition and acid treatment for NO absorption

Wet scrubbing of NOx was accomplished by hexamminecobalt(II) solution in a laboratory setting, and the spent absorbent was regenerated by thermal decomposition and acid treatment. The spent absorbent contained precipitates (cobalt nitrosyl) and soluble cobalt in the solution. Thermogravimetric analysis (TGA) showed that the spent sorbent could be decomposed to CoO at temperatures above 900 circle C. Caution needed to be exercised to ensure that the samples were not exposed to oxygen when cooling down to ambient temperature in order to prevent oxidation of CoO to Co3O4. The regenerated cobalt (II) oxide was dissolved in HCI for preparation of hexamminecobalt(II) solutions, and such a regenerated cobalt-based sorbent for NO removal performed at the same level as the fresh one. This study suggests a practical method for the regeneration of a cobalt-based absorbent involved in NO absorption. (C) 2017 Elsevier B.V. All rights reserved.