Decoupling the influence of NOx in flue gas on the application of nano-amorphous selenium for mercury removal

• Published in: The Science of the total environment 2024-11, Vol.951, p.175698, Article 175698
• Main Authors: Wang, Li, Li, Yu, Sun, Ruize, Zou, Renjie, Huang, Yongda, Yu, Mingyu, Liu, Jing, Luo, Guangqian, Yao, Hong
• Format: Article
• Language: English
• Subjects: Flue gas; Influence mechanism; Mercury; Nano-amorphous selenium; Nitrogen oxides
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.175698

Nitrogen oxides are inevitable hazardous components in coal-fired flue gas. This study designed a series of experiments and combined theoretical calculations to systematically investigate the effect of NOx on the removal of element mercury (Hg0) by nano-amorphous selenium (nano-a-Se). It was found that the impact of NOx on the removal of Hg0 by nano-a-Se primarily involves two mechanisms: competitive adsorption between NOx and Hg0, and the induced reduction effect of NOx on chemisorbed mercury (HgSe). NO inhibits the removal of Hg0 by nano-a-Se, and competitive adsorption is identified as the main influencing factor. Whereas the inhibitory effect of NO2 on the adsorption of Hg0 by nano a-Se can be counteracted due to its oxidizing effect on Hg0. Therefore, although NO2 presents stronger competitiveness than NO in the competitive adsorption with Hg0, it still shows a promoting effect on Hg0 removal, with 50 ppm NO2 restoring 5.7 % of the Hg0 removal efficiency. Additionally, the mechanism of NOx-induced reduction of HgSe was investigated in detail. NO2 is more capable of inducing the reduction of Hg(II) from HgSe to Hg0. This study presents new insights into the underlying influence mechanism, which could provide valuable references for the application of other selenium-based adsorbents. [Display omitted] •NOx has a certain induced reduction effect on HgSe.•NO2 exhibits stronger competitive adsorption and induced reduction effects than NO.•NO2 promotes Hg0 removal mainly due to its oxidizing effect on Hg0.•The impact of NOx on the Hg0 removal efficiency was comprehensively decoupled.