A new approach for Fe(III)EDTA reduction in NO(x) scrubber solution using bio-electro reactor

Area of Science:

• Environmental Science
• Biotechnology
• Chemical Engineering

Background:

• Nitrogen oxides (NOx) are major air pollutants contributing to environmental issues.
• Flue gas treatment often involves chemical absorption, like using Fe(II)EDTA, which can oxidize to Fe(III)EDTA.
• Microbial reduction offers a sustainable alternative for pollutant removal, with Strain FR-2 known for Fe(III)EDTA reduction.

Purpose of the Study:

• To investigate the use of a bio-electro reactor to enhance the microbial reduction of Fe(III)EDTA by Strain FR-2.
• To optimize the conditions for Fe(III)EDTA reduction in a combined absorption-microbial process for NOx removal.
• To evaluate the impact of electrical parameters and co-existing substances on the reduction efficiency.

Main Methods:

• A bio-electro reactor system was employed, utilizing Strain FR-2 immobilized on an electrode.
• Fe(II)EDTA was introduced, and its oxidation product, Fe(III)EDTA, was subjected to microbial reduction under applied electrical current.
• Environmental Scanning Electron Microscopy (ESEM) was used to observe biofilm formation on the electrode.
• Experiments were conducted varying current density and introducing sodium nitrite (NaNO2) to assess their effects.

Main Results:

• The application of electric current significantly accelerated the reduction of Fe(III)EDTA.
• Fe(III)EDTA reduction rate increased with rising current density up to a certain point, after which it decreased.
• Biofilm formation on the electrode surface was confirmed via ESEM.
• The presence of NaNO2 notably inhibited the Fe(III)EDTA reduction rate.

Conclusions:

• A bio-electro reactor effectively promotes the microbial reduction of Fe(III)EDTA by Strain FR-2, enhancing NOx removal processes.
• Optimizing current density is crucial for maximizing the efficiency of Fe(III)EDTA reduction.
• The microbial community's activity is sensitive to co-contaminants like NaNO2, impacting the overall process effectiveness.