Magnetic Fe3O4/activated carbon for combined adsorption and Fenton oxidation of 4-chlorophenol

Abstract Development of composite adsorbents having high removal efficiency as well as convenient separation and regeneration properties is important for water treatment. This study synthesized magnetic activated carbon (MAC) from activated carbon (AC) by impregnation of iron oxides in the porous structure. Systematic characterization results demonstrated that MAC contained Fe3O4 and had size of ∼0.5 mm, saturated magnetization of 8.99 emu/g, specific surface area of 473 m2/g, and pore volume of 0.54 cm3/g. Batch adsorption experiments were conducted using 4-chlorophenol (4-CP) as the probing pollutant and both MAC and AC as the adsorbents. Results showed that the adsorption rate followed intra-particle diffusion model and pseudo-second-order rate model, and that the adsorption equilibrium can fit to Freundlich isotherm equation. After adsorption, H2O2 was added to initiate a heterogeneous Fenton reaction catalyzed by impregnated Fe3O4 on MAC. More than 90% of aqueous 4-CP was degraded within 1 h, with optimal conditions of pH 3.0, 20 mM H2O2, and Fe2+/Fe3+ ratio of 3:1. After 5 cycles of adsorption-regeneration, the MAC composite remained >80% removal efficiency for 4-CP, indicating that it could be reused as an effective and retrievable adsorbent in water treatment of organic pollutants.