Nitric oxide absorption into cobalt ethylenediamine solution

NO pollutant causes acid rain and urban smog. The removal of NO from exhausted gas streams is necessary to meet stringent effluent discharge limits. NO can be removed from exhausted gas streams by putting soluble cobalt salts and ethylenediamine (H2NCH2CH2NH2) into basic solutions. The Co(en)33+ (en stands for ethylenediamine) ion produced by ethylenediamine binding cobalt acts as a homogeneous catalyst to oxidize NO into soluble NO2 and realize the oxidation and absorption of nitric oxide in the same reactor. The dissolved oxygen in equilibrium with the residual oxygen in the exhausted gas stream acts as the oxidant. The experiments manifest that this process is superior to the methods using Fe(II)–ethylenediaminetetraacetate (EDTA) solution and H2O2 solution as absorbents in removing NO from the exhausted gas stream. NO removal efficiency decreases with the increase of the gas flow rate. NO removal efficiency increases with the Co(en)33+ concentration. pH of the solution affects the NO removal efficiencies obviously. Under anaerobic condition, the NO removal efficiency decreases with pH when pH is over 7.73. Under aerobic condition, there is an optimal pH for NO absorption into the Co(en)33+ concentration. More than 90% of NO in the feed gas can be removed by the Co(en)33+ solution.