Removal Of Nitiric Oxide By Fe～Ⅱ(EDTA) Chelate Absorption Combined With Microbial Reduction

The pollution of nitric oxides (NOX) is received increasing attention with the increasing emission amount of NOX and the increasing requirement of people on environmental quality. Many countries have established stringent regulations on NOX emissions. Current technologies for NOX removal from flue gas have associated with some problems, such as high cost, produced secondary pollutant and/or low removal efficiency. On the other hand, the difficulty in removal of NOX from flue gas was increased due to the large emission amount of flue gas and the low solubility of NO, which is the main component of NOX in flue gas. The research on NOX removal from flue gas is becoming a hot issue of air pollution control presently.The newly proposed and adopted method in our work for NOX removal from flue gas, i.e. metal chelate absorption combined with microbial reduction, is deemed as a promising method, and possesses with the characteristics of low cost, completely reduction of NO and high removal efficiency. The reduction properties of microorganisms under the conditions of shaking flasks and continuous operation, the isolation of microorganisms and the process of continuously steady removal of NO were investigated. The mechanism and the preliminary kinetics of this process were analyzed. The aim of this work was to provide a new method and some fundamental data for NOX removal from flue gas. The main experimental results were as follows:(1) The reduction performance of cultivated microorganisms was investigated in the flask culture experiments. The results showed that it was effective to reduce Fen(EDTA)NO and Fem(EDTA) by cultivated microorganisms with the adding of carbon sources. Among the carbon sources investigated, glucose was suitable for the reduction of Fen(EDTA)NO and Feni(EDTA), and ethanol was benefit to the growth of Fen(EDTA)NO reduction bacteria. The optimal reduction pH and temperature range were 6-7 and 30~40℃. The bio-reduction could be achieved efficiently with enough carbon source and cell inoculation. The reduction rate did not increase with adding more amount of carbon source or cell inoculation. The bio-reduction rate could be described by Michaelis-Menten equation and fitting to the first order reaction kinetics. For Feu(EDTA)NO and Fem(EDTA) reduction, the maximum reaction rates ymax were 5.4 mmol.L-1.h-1 and 1.3 mmol-L-1.h-1 and the Michaelis constant k were 63.8 mmol-L-1 and 53.5mmmol-L-1 respectively.(2) Two bacterial strains DN-1 and FR-1 isolated from the cultivated cultures were employed effectively to reduce FeII(EDTA)NO and Fem(EDTA). According to their physiological and morphological properties, FeI!(EDTA)NO reduction strain DN-1 was identified as Pseudomonas sp and FeIII(EDTA) reduction strain FR-1 was identified as klebsiella trevisan sp. Their growth and reduction characteristics were also investigated. The results indicated that the mixture of yeast extract and glucose as a carbon source was benefit to the growth of DN-1. Glucose was more suitable for FeII(EDTA)NO reduction than other carbon sources of sodium acetate, sodium citrate and ethanol, and it was also the best carbon source for FR-1 growth andreduction. With the same reduction characteristics as cultivated cultures, the reduction rates of FeII(EDTA)NO and FeIII(EDTA) by DN-1 and FR-1 did not increase with adding more amount of carbon source. To avoid the suppression of NO3-, NH4CL was selected as nitrogen source for FR-1 growth and the optimal adding amount was 100 mg.L-1. Reduction efficiencies of FeII(EDTA)NO and FeIII(EDTA) by DN-1 and FR-1 were increased with the increasing of the amount of cell inoculation. The maximal growth of FR-1 was obtained at 100mg.L-1 cell inoculation. Reduction of Fen(EDTA)NO by DN-1 could be achieved efficiently among the temperature range of 40~45# and a pH range of 6.9~7.2. The suitable temperature range for FR-1 growth and FeIII(EDTA) reduction was 30~40#. During the pH range of 5.0-8.5, FR-1 growth decreased and FeIII(EDTA) reduction efficiency increased with the increasing of initia...