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Zusammenfassung:
Mercury removal from coal combustion flue gas remains a great challenge for environmental protection because of the lack of cost-effective sorbents. This study prepared a series of bentonites modified with Ce-Fe binary oxides (CeXFe4-X/Ben) for elemental mercury (Hg0) capture from flue gas. The textural properties, crystal structure, magnetic properties, redox properties, and surface chemistry of CeXFe4-X/Ben were characterized. The results testified that modification procedure had little effect on the pore shape and pore size of bentonite. During modification process, a synergistic effect occurred between iron oxide and cerium oxide and Ce-Fe binary oxides entered the interlayer of bentonite. The CeXFe4-X/Ben samples presented far better Hg0 removal performance compared with raw, Fe-modified, and Ce-modified bentonite. The optimum Ce/Fe molar ratio and adsorption temperature were 2:2 and 150–200 °C, respectively. O2, NO, and HCl promoted Hg0 removal whereas SO2 and H2O inhabited Hg0 removal. The Hg0 removal process was dominated by heterogeneous adsorption and CeXFe4-X/Ben was used as a sorbent. Furthermore, the Hg0 removal mechanism was revealed, where CeO2 and Fe2O3 served as active sites for Hg0 removal. Multiple adsorption-regeneration cycles demonstrated that the deactivated CeXFe4-X/Ben could be effectively regenerated after thermal treatment at 400 °C for 1 h under air atmosphere.
