Selenium catalyzed Fe(III)-EDTA reduction by Na2SO3: a reaction-controlled phase transfer catalysis
2016
Xiang, Kaisong | Liu, Hui | Yang, Bentao | Zhang, Cong | Yang, Shu | Liu, Zhilou | Liu, Cao | Xie, Xiaofeng | Chai, Liyuan | Min, Xiaobo
Fe(II)-EDTA, a typical chelated iron, is able to coordinate with nitric oxide (NO) which accelerates the rates and kinetics of the absorption of flue gas. However, Fe(II)-EDTA can be easily oxidized to Fe(III)-EDTA which is unable to absorb NO. Therefore, the regeneration of fresh Fe(II)-EDTA, which actually is the reduction of Fe(III)-EDTA to Fe(II)-EDTA, becomes a crucial step in the denitrification process. To enhance the reduction rate of Fe(III)-EDTA, selenium was introduced into the SO₃ ²⁻/Fe(III)-EDTA system as catalyst for the first time. By comparison, the reduction rate was enhanced by four times after adding selenium even at room temperature (25 °C). Encouragingly, elemental Se could precipitate out when SO₃ ²⁻ was consumed up by oxidation to achieve self-separation. A catalysis mechanism was proposed with the aid of ultraviolet–visible (UV–Vis) spectroscopy, Tyndall scattering, horizontal attenuated total reflection Fourier transform infrared (HATR-FTIR) spectroscopy, and X-ray diffraction (XRD). In the catalysis process, the interconversion between SeSO₃ ²⁻ and nascent Se formed a catalysis circle for Fe(III)-EDTA reduction in SO₃ ²⁻ circumstance.
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