Elemental mercury (Hg0) removal from coal syngas using magnetic tea-biochar: Experimental and theoretical insights

Mercury is ranked 3rd as a global pollutant because of its long persistence in the environment. Approximately 65% of its anthropogenic emission (Hg-0) to the atmosphere is from coal-thermal power plants. Thus, the Hg-0 emission control from coal-thermal power plants is inevitable. Therefore, multiple sorbent materials were synthesized using a one-step pyrolysis method to capture the Hg-0 from simulated coal syngas. Results showed, the Hg-0 removal performance of the sorbents increased by the citric acid/ultrasonic application. TSCUF0.3 demonstrated the highest Hg-0 capturing performance with an adsorption capacity of 106.81 mu g/g within 60 min at 200 degrees C under complex simulated syngas mixture (20% CO, 20% H-2, 10 ppmV HCl, 6% H2O, and 400 ppmV H2S). The Hg-0 removal mechanism was proposed, revealing that the chemisorption governs the Hg-0 removal process. Besides, the active Hg-0 removal performance is attributed to the high dispersion of valence Fe3O4 and lattice oxygen (alpha) contents over the T5CUF(0.3) surface. In addition, the temperature programmed desorption (TPD) and XPS analysis confirmed that H2S/HCl gases generate active sites over the sorbent surface, facilitating high Hg-0 adsorption from syngas. This work represented a facile and practical pathway for utilizing cheap and eco-friendly tea waste to control the Hg-0 emission. (C) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Automated summary

This study synthesized multiple sorbent materials and improved the Hg-0 removal performance from coal syngas by applying citric acid/ultrasonic treatment. TSCUF0.3 demonstrated the highest Hg-0 capturing performance and the removal mechanism was proposed. The active Hg-0 removal performance was attributed to the valence Fe3O4 and lattice oxygen content on the sorbent surface, as well as the activation by H2S/HCl gases. This work provides a practical approach for utilizing cheap and eco-friendly tea waste to control Hg-0 emission.