One-step preparation of coal-based magnetic activated carbon with hierarchically porous structure and easy magnetic separation capability for adsorption applications

Abstract

Coal-based magnetic activated carbons (CMACs) were prepared from Zhundong coal in the presence of various Fe-based additives by fast one-step physical activation method. The roles of types and doses of Fe sources for pore structures and magnetic properties of the resulting CMACs were systematically investigated. Fe species in coal promoted the development of mesopore structures, and AC-FC-3 derived from FeCl3-loaded coal (3% Fe content) possessed hierarchical pore structure with highest micropore and mesopore volumes up to 0.282 cm3·g−1 and 0.222 cm3·g−1, respectively. Considering the minimum dose of additives, the CMACs loaded a trace amount of reduced iron powder (0.5% and 1% weight ratios of coal) were prepared, and had improved micropore and mesopore structures compared with AC derived from the demineralized coal. Meanwhile, strong magnetic iron oxides (Fe3O4 and γ-Fe2O3) were generated during CO2 activation process. The CMACs derived from different Fe sources loaded coal samples with same Fe content (3% weight ratio of coal) had saturation magnetizations of 0.55–14.26 emu·g−1. Evaluated as adsorbents for Methylene Blue (MB) removal, the CMACs with hierarchical pore structure exhibited better MB adsorption capacities up to 120.3 mg·g−1. Furthermore, the magnetic properties of CMAC could accelerate the solid–liquid separation with an applied magnetic field and improve recovery efficiency of the adsorbent.