Sulfur dioxide and nitric oxide concentration reduction technology in exhaust gas based on electrochemistry

Abstract

The first chapter reports on the performance of the sulfite/FeIIIEDTA (Ferric ethylenediaminetetraacetic acid) fuel cell, in which dissolved sulfur dioxide ($SO_2$), sulfite ($SO_3^{2-}_(aq)$), is oxidized to treat $SO_2$ emitted from flue gas. As a terminal electron acceptor, FeIIIEDTA was harnessed to regenerate the absorbent of nitric oxide (NO), that is FeIIEDTA. The effects of various operating parameters, such as reactants concentrations, pH of reactants, and operating temperature, on the performance of the fuel cell were investigated. The highest performance was obtained of 7.51 mW $cm^{-2}$ with the anode solution of 1 M $Na_2SO_3$ and 1 M NaOH and the cathode solution of 100 mM FeIIIEDTA and 1 M HCl at 80 $\circ C$. After the 6-hour discharge of the fuel cell at 0.1V, the quantity of the products were analyzed and the faraday efficiency about the FeIIEDTA was turned out to be 55.5 %. The durability of the fuel cell was also tested, resulting in a stable operation for 30 hours. This fuel cell is expected to alleviate air pollution by removing $SO_2$ and regenerate NO absorbent simultaneously with the electrical energy generation. In the second chapter, the dry-type adsorbent for nitric oxide removal was synthesized. The supporting material was graphene oxide, and it was functionalized with EDTA-silane to impose the metal chelating ability. Then prepared adsorbent was reduced by hydrazine in order to gain the electrical conductivity for its regeneration in case of iron oxidation caused from the oxygen in the flue gas. Then iron was chelated to the adsorbent because FeIIEDTA is well known for its nitric oxide capturing ability.