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Removal of elemental mercury from coal combustion flue gas using recyclable Dy modified Mn-Fe mixed oxide nanoparticles

2022; Elsevier BV; Volume: 10; Issue: 5 Linguagem: Inglês

10.1016/j.jece.2022.108493

2213-3437

Yan Shao, Jinhang Fan, Jiayi Li, Jiangxiu Yang, Yuan Wang, Hongcheng Ruan, Zihao Liu, Honghu Li, Yifei Long, Jiangjun Hu,

Geochemistry and Elemental Analysis

To enhance its SO 2 tolerance and further improve the Hg 0 removal performance, Dy was applied to modify the Mn-Fe mixed oxide sorbent. Results showed that appropriate Dy addition promoted the Mn 3 O 4 formation, decreased the grain size, enlarged the surface area, increased the chemisorbed oxygen concentration and weak acid sites of sorbent, thus promoting its Hg 0 removal performance. The calcination at excessive high temperature would result in the grain growth and decrease the sorbent activity. MnFeDy 0.4 -400 (with Dy/Fe molar ratio of 0.4 and calcined at 400 °C) exhibited the best Hg 0 removal performance. Around 86% Hg 0 removal could be achieved over MnFeDy 0.4 -400 under 5% O 2 , 300 ppm NO, 1000 ppm SO 2 and 3% H 2 O. O 2 could replenish the active oxygen species and maintain the surface metal ions at high-valent state, which was essential to Hg 0 removal. With presence of NO, abundant active nitrogenous species could form over MnFeDy 0.4 -400 surface, contributing to the Hg 0 removal. Due to strong basicity, Dy species functioned as a SO 2 trap agent to preserve the predominant active species Mn 3 O 4 , thereby improving the capacity of sorbent to resist SO 2 . The formation of active nitrogenous species over MnFeDy 0.4 -400 would not be significantly affected by SO 2 . Moreover, MnFeDy 0.4 -400 had superparamagnetic property. This enabled spent MnFeDy 0.4 -400 to be separated from fly ash by magnetic separation. Regeneration and stability evaluation tests manifested that MnFeDy 0.4 -400 might be a promising material that could be utilized for Hg 0 removal from flue gas. • MnFeDy 0.4 -400 showed good Hg 0 removal performance and tolerance to SO 2 . • Appropriate Dy addition and calcination temperature contributed to nano-Mn 3 O 4 formation. • Dy species functioned as a SO 2 trap agent to preserve the predominant active species Mn 3 O 4 . • The magnetically responsive MnFeDy 0.4 -400 could be separated from fly ash by magnetic separation.