| NOx emission is one of air pollution problems committed to figure out in China.Selective catalytic reduction (SCR) is the major technology of flue gasdenitrification (De-NOx). In spite of this, SCR encounters some problems, such ascatalyst poisoning, high operating costs and secondary pollutions. c (Fe(Ⅱ)EDTA asthe representative) can absorb NOx specifically with the formation ofFe(Ⅱ)EDTA-NO, which resolves NO gas-liquid mass transfer resistance andprovides a promising alternative for De-NOx. However, the regeneration of ferrouschelators requires large amounts of organic matters or energy. Therefore, establishingnew regeneration methods with less material or energy consumption is urgent.MFCs are considerd as a promising alternative power source due to its uniqueability of simultaneous waste water treatment and electricity generation. Based onthe feature of MFC, we propose a method of simultaneous ferrous chelatorregeneration and wastewater treatment with NO chelating complex (mainlyFe(Ⅲ)EDTA and Fe(Ⅱ)EDTA-NO) being MFC catholyte. The effects of differentexternal resistances, pH and initial concentrations of catholyte on Fe(Ⅲ)EDTA andFe(Ⅱ)EDTA-NO reduction and electricity generation characteristics are investigated.Further, Fe(Ⅲ) reducing microorganisms and denitrifying bacteria were introducedcorresponding into cathodes to improve the performance of MFC. Reduction andelectricity generation characteristics of Fe(Ⅱ)EDTA-NO under the conditions ofchemical cathode and biocathode are preliminary discussed. The results are asfollows:(1) Fe(Ⅲ)EDTA and Fe(Ⅱ)EDTA-NO can be used as cathode electron acceptorsto promote MFC operation and Fe(Ⅱ)EDTA regeneration with, electricity generationsimultaneously.(2) In chemical cathode, the pH value and initial concentration of catholytehave obvious effect on electricity generation and Fe(Ⅱ)EDTA regeneration in MFC. Low pH causes Fe(Ⅲ)EDTA transforming to the free ions, and then increases thepotential of cathode. Proton is needed to reduce Fe(Ⅱ)EDTA-NO and lower pH alsocan enhance MFC performance. The maximum current density and power density ofMFC was19A/m~3and2.02W/m~3in pH=5.0more than11A/m~3and1.28W/m~3inpH=7.0, respectively.(3) Compared to the chemistry cathode, biocathode does well in electricitygeneration and reduction for Fe(Ⅲ)EDTA and Fe(Ⅱ)EDTA-NO. The output currentof MFC in Fe(Ⅲ)EDTA biocathode was0.5mA, higher47%than0.34mA inFe(Ⅲ)EDTA chemistry cathode. The reduction efficiency of Fe(Ⅲ)EDTA was fasterin Fe(Ⅲ)EDTA biocathode than chemistry cathode. When initial concentration ofFe(Ⅲ)EDTA was1mM, biocathode reduction efficiency achieved80%at fourthhour,20%higer than chemistry cathode. The reduction efficiency ofFe(Ⅱ)EDTA-NO was the same as Fe(Ⅲ)EDTA,68%to52.7%at third hour.(4) The molecular biology measurements of microorganisms in the anode,Fe(Ⅲ)EDTA biocathode and Fe(Ⅱ)EDTA-NO biocathode of biofuels indicated thatelectricigens in anode mainly included Comamonas sp. and Cupriavidus basilensis;the dominant species in Fe(Ⅲ)EDTA biocathode were Ochrobactrum sp.,Comamonas sp. and Rhodococcus ruber; in addition to denitrification bacteria suchas Azonexus and Stenotrophomonas sp., there were a lot of Ochrobactrum sp. inFe(Ⅱ)EDTA-NO biocathode.(5) During Fe(Ⅱ)EDTA-NO reduction in MFC, a certain amount ofFe(Ⅲ)EDTA was accumulated in chemical cathode condition, while thisphenomenon can not be found in biocathode. Fe(Ⅲ)EDTA reduction process couldbe accelerated by ferric-reducing bacteria in Fe(Ⅱ)EDTA-NO biocathode.Meanwhile, part of Fe(Ⅱ)EDTA-NO can be reduced by denitrification bacterias. |
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