Removal of elemental mercury from coal combustion flue gas using bentonite modified with Ce-Fe binary oxides

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 (Hg-0) 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 Hg-0 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 degrees C, respectively. O-2, NO, and HCl promoted Hg-0 removal whereas SO2 and H2O inhabited Hg-0 removal. The Hg-0 removal process was dominated by heterogeneous adsorption and CeXFe4X/Ben was used as a sorbent. Furthermore, the Hg-0 removal mechanism was revealed, where CeO2 and Fe2O3 served as active sites for Hg-0 removal. Multiple adsorption-regeneration cycles demonstrated that the deactivated CeXFe4-X/Ben could be effectively regenerated after thermal treatment at 400 degrees C for 1 h under air atmosphere.