Nitric oxide removal from flue gas by combined persulfate and ferrous EDTA solutions: Effects of persulfate and EDTA concentrations, temperature, pH and SO2
Abstract The effects of persulfate (PS) and ethylenediaminetetraacetate (EDTA) concentrations at different temperature and pH on the removal of NO were studied using combined Na2S2O8 and Fe2+ EDTA aqueous solutions. The experiments were conducted in the temperature and pH ranges of 23 70 degC and 2 12, respectively, using 0.05 0.20 M PS and 0.01 M Fe2+ in the absence and presence of 0.005 0.050 M Na2 EDTA. The effect of SO2 was also preliminarily investigated. Increased temperature led to increased conversions of NO (percent inlet NO removed) at all PS levels but high concentrations of EDTA produced antagonistic effects with increasing temperature. With 0.10 M Na2S2O8, 0.01 M Fe2+ and 0.01 M EDTA, NO conversion increased with temperature from 23 to 70 degC. At 70 degC, NO conversion increased from 83.40 96.28% as EDTA concentration increased from 0.005 to 0.01 M EDTA but decreased to 29.22 and 0.4% with 0.02 and 0.05 M EDTA, respectively. The results at 40 and 50 degC showed optimal NO conversions in the pH range 6 8, and higher at 50 degC. However, at higher pH >11) NO conversion is higher at 40 degC than at 50 degC. The speciation and material balance of the iron species were determined at different Fe2+ and EDTA concentrations. The results, which showed sustained NO absorption at lower temperatures and mid pH, could in practice minimize process pH adjustment and energy usage in wet scrubbers. The process could be applicable to the simultaneous cleanup of NOx and SO2 from oil and coal fired power plant and industrial boiler.