Performance and mechanism of oxidation, and removal of trace SeO2 in flue gas utilizing a H2O2, NaClO2, and Ca2+ slurry

• Published in: Environmental science and pollution research international 2021-08, Vol.28 (31), p.42934-42944
• Main Authors: Ma, Jingxiang, Zhao, Yi, Wei, Yanan
• Format: Article
• Language: English
• Subjects: Absorbents; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Calcium carbonate; Calcium hydroxide; Calcium ions; Chlorine; Chlorine dioxide; Coal-fired power plants; Earth and Environmental Science; Ecotoxicology; Electrons; Environment; Environmental Chemistry; Environmental Health; Environmental science; Flue gas; Fluorescence; Free radicals; Hydrogen peroxide; Hydroxyl radicals; Oxidation; pH effects; Photoelectron spectroscopy; Photoelectrons; Power plants; Research Article; Selenite; Selenites; Selenium; Selenium dioxide; Slaked lime; Slurries; Sodium chlorite; Spectrometry; Trace elements; Waste Water Technology; Water Management; Water Pollution Control
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-021-13456-x

Selenium (Se) is one of the toxic trace elements in flue gas emitted from coal-fired power plants. A method for oxidation and absorption of selenium dioxide (SeO 2 ) by hydrogen peroxide (H 2 O 2 ) and sodium chlorite (NaClO 2 ) in a calcium-based slurry is proposed, in which hydrated lime (Ca(OH) 2 ) and calcium carbonate (CaCO 3 ) were selected to be absorbents, and H 2 O 2 and NaClO 2 were used to oxidize SeO 2 and selenite ion to selenate ion to reduce their toxicities. The effects of reaction temperature, H 2 O 2 and NaClO 2 concentrations, solution pH, and SeO 2 concentration were investigated, from which the optimal reaction conditions were established. The results indicated that the oxidation efficiency was affected significantly by the solution pH, and H 2 O 2 and NaClO 2 concentrations. The oxidation efficiency of SeO 2 and selenite ion to selenate ion was below 40% using H 2 O 2 and that increased to 92% with NaClO 2 at the optimal conditions. For removal, Ca(OH) 2 and CaCO 3 slurries were used as absorbents and the efficiencies were affected by the slurry temperature. Oxidation behavior and mechanism were analyzed based on the characterization of removal products using hydride generation-atomic fluorescence spectrometry and X-ray photoelectron spectroscopy. SeO 2 and selenite ion can be oxidized to selenate ion, which is less toxic, by active species such as hydroxyl radicals (HO·) and chlorine dioxide (ClO 2 ), which are released during the decomposed processes of H 2 O 2 and NaClO 2 in acid conditions.