The Synthesis of FeCl₃-Modified Char from Phoenix Tree Fruit and Its Application for Hg⁰ Adsorption in Flue Gas

A sample of FeCl3-modified phoenix tree fruit char (MPTFC) was prepared using pyrolysis and a facile chemical immersion method; it was proposed as an effective sorbent for Hg0 adsorption in flue gas. The BET, SEM, FTIR, and XPS methods were adopted for the characterizations of the sorbents, and a series of Hg0 adsorption tests were conducted on a bench-scale Hg0 removal setup in the lab. The morphological analysis of the sorbent indicated that the hollow fiber in phoenix tree fruit (PTF) shifted to organized directional porous tubular columns in phoenix tree fruit char (PTFC) after pyrolysis. The surface area of MPTFC increased slightly in comparison with PTF and PTFC. The MPTFC showed excellent performance for Hg0 adsorption at 200 °C in flue gas ambiance, and the Hg0 removal efficiency approached 95% with 5% (wt.%) FeCl3 modification. The presence of O2 may help to activate the MPTFC for Hg0 adsorption in flue gas, thus greatly promoting Hg0 adsorption capability. NO had a positive effect on Hg0 adsorption, while the presence of SO2 in flue gas restrained Hg0 adsorption by MPTFC. Functional groups, such as C-Cl and Fe-O, were successfully decorated on the surface of PTFC by FeCl3 modification, which contributed greatly to Hg0 adsorption. In addition, C=O, lattice oxygen (Oα), and adsorbed oxygen (Oβ) also contributed to Hg0 adsorption and oxidization.