Wet ammonia desulphurization process can be retrofitted for combined removal Of SO2 and NO from the flue gas by adding soluble cobalt(II) salts into the aqueous ammonia solutions. The Co(NH3)(6)(2+) formed by ammonia binding with Co2+ is the active constituent of scrubbing NO from the flue gas streams. A stirred vessel with a plane gas-liquid interface was used to measure the chemical absorption rates of nitric oxide into the Co(NH3)(6)(2+) solution under anaerobic and aerobic conditions separately. The experiments manifest that the nitric oxide absorption reaction can be regarded as instantaneous when nitric oxide concentration levels are parts per million ranges. The gas-liquid reaction becomes gas film controlling as Co(NH3)(6)(2+) concentration exceeds 0.02 mol/l. The NO absorption rate is proportional to the nitric oxide inlet concentration. Oxygen in the gas phase is favorable to the absorption of nitric oxide. But it is of little significance to increase the oxygen concentration above 5.2%. The NO absorption rate decreases with temperature. The kinetic equation of NO absorption into the Co(NH3)(6)(2+) solution under aerobic condition can be written as N-NO = K(NO,G)k(4)K(1) (p(NO) + gamma C-Co(NH3)62+ L,C-)C-Co(NH3)62+(2) (L,) p(o2)/k(-3) + k(4)K(1)C(Co(NH3)62+,LpO2)(2) (c) 2005 Elsevier B.V. All rights reserved.