A New Approach For Fe(Ⅱ)EDTA-NO And Fe(Ⅲ)EDTA Reduction In NO_x Scrubber Solution Using Bio-electro Reactor

A new process for the removal of NO_x from flue gas by a combined Fe(II) EDTA absorption and microbial reduction has been demonstrated. During the process, NO_x can be absorbed by Fe(II)EDTA solution efficiently to form Fe(II)EDTA-NO and part of Fe(II)EDTA will be oxidized by oxygen in the flue gas to form Fe(III)EDTA, which can be biologically regenerated by strain DN-2 and strain FR-2 in our former studies. Otherwise, it has been reported that bio-electro reactor could efficiently provide a chance for simultaneous denitrification and metal ion removal. Therefore, a use of bio-electro reactor is suggested to promote the reduction of Fe(II)EDTA-NO and Fe(III)EDTA in NO_x scrubber solution in this paper. This study use Fe(II)EDTA as absorption solution and bacterial strains isolated from the cultivated cultures are inoculated to the bio-electro reactor. As a new promising method, bio-electro reactor is adopted to convert Fe(II)EDTA-NO and Fe(III)EDTA to Fe(II)EDTA, while the absorption solution is regenerated.The character and reduction ability of the strain FR-2 , DN-2 and the mixture of two strains was studied. During the biofilm startup period, the mixture of strain FR-2 and strain DN-2 was inoculated into the reactor. The effect of current density on the reduction of Fe(II)EDTA-NO and Fe(III)EDTA was investigated. SEM was employed to confirm the biofilm formation on the electrode and analyse the state of bacteria. It was analysed the biological reduction, electrochemical reduction and electrochemical combined with biological reduction of Fe(II)EDTA-NO and Fe(III)EDTA in the bio-electro reactor. We find out that the electric current can promote the growth of cells.After the cultivation, the impacts of reactor operating and the concentration of Fe(II)EDTA-NO and Fe(III)EDTA on NO_x scrubber solution reduction were studied. The results showed that the reduction rate of Fe(III)EDTA and the generation rate of Fe(II)EDTA was both decreased rapidly when the concentration of Fe(II)EDTA-NO rose. The reduction of Fe(II)EDTA-NO and Fe(III)EDTA can not be occured when there is no electric current in the reactor. The maximum generation rate of Fe(II)EDTA was attained when the current density was 0.09 mA cm^-2 (I=0.03 A).