Nitric oxide removal by combined persulfate and ferrous–EDTA reaction systems

Abstract

Nitric oxide (NO) removal from simulated flue gas is investigated using combined aqueous persulfate (Na 2 S 2 O 8 ) and ferrous ethylenediaminetetraacetate (Fe 2+ -EDTA) systems. The results at 23-70 °C showed significant improvement in NO removal using the optimally obtained molar ratio of 1:1 for the Fe 2+ and EDTA compared with temperature-only and combined temperatureFe 2+ activated persulfate systems with 0.1 M Na 2 S 2 O 8 and 0.01 M Fe 2+ in the absence of EDTA.Almost 100% NO conversion can be achieved at 70 °C (flue gas treatment inlet temperature generally at 50-70 °C) compared to temperature and Fe 2+ -activated persulfate systems which require ≥ 90 °C for such high removal efficiency. The percentage increases in NO removal were dependent on temperature, 25-30% and 5-10% at the lower (< 40 °C) and higher (> 40 °C) temperatures, respectively. A very high concentration of Fe II -EDTA appears to negatively impact NO removal. However, this process operates at an optimal NO removal pH of near neutral (~6.5) with efficiency decreasing at very low or high pH. This should reduce the use of auxiliary chemical for pH adjustment and help mitigate the important technological hurdle of undesired ferric product formation associated with Fe 2+ -only activated persulfate and other Fenton-like systems at pH (>3.5). The material balance on iron species (Fe 2+ , Fe 3+ and Fe 2+ -EDTA) was determined to better understand the chemistry of persulfate with Fe 2+ -EDTA for NO removal.The results demonstrate the feasibility of near complete NO removal at relatively lower temperatures (with the advantage of reduced energy usage), and sustained longtime high NO absorption capability.

The Chemical Behaviors of Nitrogen Dioxide Absorption in Sulfite Solution

“…Sci. 2017, 7, 377 2 of 10 oxidation have been reported [5][6][7][8][9][10][11][12], including gas phase catalytic oxidation, ozone oxidation, corona discharge oxidation, and liquid oxidation. After oxidation, the soluble NO2 can be further removed with SO2 in the subsequent absorption process [13].…”

Evaluation of FeIIEDTA‐NO reduction by thiourea dioxide in NO removal with FeIIEDTA

“…However, these regenerating agents were only used as reducing agents on the transformation from Fe III EDTA into Fe II EDTA but neglected to reduce Fe II EDTA-NO. [17][18][19] In addition, sulfite, bisulfite, activated carbon, and selenium were shown relatively weak reducibility on Fe III EDTA transformation, and dithionite and hydrazine were readily deteriorated in air, losing the strong reducing power. Besides, different bacteria such as Pseudomonas sp.…”

Removal of nitric oxide from flue gas using sulfate/hydroxyl radicals from activation of oxone with cobalt and high temperature

“…Emission of uncontrolled amounts of NO x and SO 2 into the atmosphere from the combustion of fossil fuel has severe and detrimental effects on plants, animals and humans . NO x and SO 2 are the major contributor to photochemical smog and acid rain, which harms environment and human health . Compared to SO 2 and NO 2 , which are quite easily removed by wet flue gas scrubbing process (e.g., limestone‐based wet flue gas desulfurization process).…”

“…Compared to SO 2 and NO 2 , which are quite easily removed by wet flue gas scrubbing process (e.g., limestone‐based wet flue gas desulfurization process). NO, as the main component of NO x , is much more difficult to remove because it is very sparingly soluble in aqueous solutions . Therefore, developing efficient NO control technologies is currently a hot issue in the flue gas purification field.…”

“…The wet methods mainly include oxidation absorption, sonochemical removal, electrochemical removal, photochemical removal, complex absorption, and reducing absorption, etc . These technologies show good prospects, but they also suffer from several forms of drawbacks, mainly including high costs, low removal efficiency, high operating temperatures, or disposal cost with some associated environmental problems . With an increase in environmental pressures, it is desirable to develop some new and cost‐effective NO control technologies.…”