Selenium catalyzed Fe(III)-EDTA reduction by Na2SO3: a reaction-controlled phase transfer catalysis

Area of Science:

• Environmental Chemistry
• Catalysis
• Chemical Engineering

Background:

• Fe(II)-EDTA is crucial for nitric oxide (NO) absorption in flue gas but easily oxidizes to inactive Fe(III)-EDTA.
• Regeneration of Fe(II)-EDTA via Fe(III)-EDTA reduction is vital for denitrification processes.

Purpose of the Study:

• To investigate selenium as a catalyst for enhancing Fe(III)-EDTA reduction.
• To explore the mechanism of selenium-catalyzed reduction and its self-separation properties.

Main Methods:

• Utilized ultraviolet-visible (UV-Vis) spectroscopy, Tyndall scattering, HATR-FTIR, and XRD to study the catalysis mechanism.
• Compared the reduction rates of Fe(III)-EDTA with and without selenium in the presence of sulfite (SO3(2-)).

Main Results:

• Selenium addition increased the Fe(III)-EDTA reduction rate by four times at room temperature (25°C).
• Elemental selenium precipitated out upon sulfite oxidation, enabling self-separation.
• A catalytic cycle involving SeSO3(2-) and nascent Se was proposed for Fe(III)-EDTA reduction.

Conclusions:

• Selenium effectively catalyzes the reduction of Fe(III)-EDTA, significantly improving denitrification efficiency.
• The self-separation property of selenium offers practical advantages for industrial applications.
• The proposed mechanism provides insights into selenium's role in redox processes.