Reduction Of Chelate Complexes In NO_x Scrubber Solution Using Three-dimensional Bio-electrode Reactor

A three-dimensional bio-electrode reactor was innovatively ultilized for the reduction of chelate complexes in NOx scrubber solution, the main components of which were Fe(â…¡)EDTA-NO and Fe(â…¢)EDTA. It was hoped that the biological reduction of Fe(â…¡)EDTA-NO and Fe(â…¢)EDTA could be improved simultaneously.Two reactors with different particle electrodes (granular activated carbon and graphite particle) were set up to form biofilm and graphite particle was found to be the prefered particle electrode. Effects of glucose concentration and current density on the biological reduction of Fe(â…¢)EDTA and Fe(â…¡)EDTA-NO was investigated and the two parameters were optimized in consideration of cost and efficiency.By comparison of Fe(â…¡)EDTA formation via Fe(â…¡)EDTA-NO and Fe(â…¢)EDTA reduction in three different methods (biological, electrochemical and bio-electrode), the three-dimensional bio-electrode reactor was verified to be advantagetous. Moreover, microbial reduction was significantly improved with electrode structure changed from two-dimensional to three-dimensional with reduction efficiency of Fe(â…¡)EDTA-NO and Fe(â…¢)EDTA up to 91.4% and 80% respectively.The preliminary analysis of the reduction process demonstrated that Fe(â…¡)EDTA served as the primary electron donor in Fe(â…¡)EDTA-NO reduction while Fe(â…¢)EDTA reduction took advantage of both added glucose and hydrogen generated from cathode as electron donor. Fe(â…¡)EDTA-NO and Fe(â…¢)EDTA had inhibition to each other's microbial reduction.Continuous operation of the reactor was also researched. Steady reduction efficiency could be maintained even without electricity supply. However, the reduction efficiency decreased significantly in the absence of glucose, indicating that heterotrophic microorganisms were domiante in the biofilm.