Preparation of magnetically separable mesoporous activated carbons from brown coal with Fe3O4

Magnetically separable mesoporous activated carbon was prepared from brown coal in the presence of Fe 3 O 4 as a bi-functional additive. Magnetic activated carbon (MAC) was characterized by low-temperature nitrogen adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometry (VSM). The evolution behaviors and transition mechanism of Fe 3 O 4 during the preparation of MAC were investigated. The results show that prepared MAC with 6 wt% Fe 3 O 4 addition having a specific surface area and mesopore ratio of 370 m 2 ·g −1 and 55.7%, which meet the requirements of adsorption application and magnetic recovery. Highly dispersed iron-containing aggregates with the size of 0.1 μm in the MAC were observed. During the preparation of MAC, Fe 3 O 4 could enhance the escape of volatiles during the carbonization. Fe 3 O 4 could also accelerate burning off the carbon wall during activation, which leads to enlarging micropore size, then resulting in the generation of mesopore and macropore. As a result, a part of Fe 3 O 4 converted into FeO, FeOOH, α-Fe, γ-Fe, Fe 2 SiO 4 and compound of Aluminum-iron-silicon. The prepared activated carbon, which was magnetized by both of residual Fe 3 O 4 , reduced α-Fe and γ-Fe, can be easily separated from the original solution by external magnetic field.