Oxidative Absorption of Elemental Mercury from Flue Gas Using a Modified Fenton-like Wet Scrubbing System
2019
Wang, Yan | Xu, Hui | Liu, Yangxian
A novel oxidative absorption process of elemental mercury (Hg⁰) from flue gas using a Mn²⁺-modified Fe³⁺/H₂O₂ wet scrubbing system (i.e., Mn²⁺-modified Fenton-like wet scrubbing system) was proposed. The influence of several technological parameters (concentration of Fe³⁺, H₂O₂, and Mn²⁺, solution pH value, solution temperature, and concentration of Hg⁰, NO, and SO₂) on Hg⁰ absorption in a bubbling stirred reactor was investigated. On the basis of the detection of free radicals and reaction products, the routes and mechanism of Hg⁰ oxidative absorption were also proposed. Results revealed that adding Mn²⁺ greatly promoted Hg⁰ absorption using a Fenton-like wet scrubbing system. The enhancement role resulted from generating more •OH radicals (they were produced from the synergistic effect of Mn²⁺ and Fe³⁺ in a Mn²⁺-modified Fenton-like wet scrubbing system). Hg⁰ removal efficiency was elevated via increasing the concentration of Fe³⁺, Mn²⁺, or H₂O₂ and was decreased by increasing the concentration of Hg⁰, NO, or SO₂. Increasing the solution temperature and pH value showed double influence on Hg⁰ absorption. Hg⁰ was oxidized by •OH and H₂O₂, and •OH played a key role. •OH was found to be produced from three sources: (1) Fe²⁺/H₂O₂ system, (2) Mn²⁺/H₂O₂ system, and (3) by the synergistic role of Fe³⁺ and Mn²⁺ in a Mn²⁺-modified Fenton-like wet scrubbing system.
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