Synthesis of magnetic biochar with high iron content and large specific surface area: Synergistic effect of Fe doping and KOH activation

Magnetic biochar has promising applications in environmental remediation, catalysts, electrode materials, etc. The influence of the sequence of iron doping process and KOH activation process on the properties of magnetic biochar is significant and has not been studied yet. In this work, the properties of magnetic biochar were evaluated by changing the order of iron doping and KOH activation, accompanied by the comparison of simultaneous these two processes. Following the doping of biochar with iron, the oxide clusters of iron distributed in the surface of the carbon skeleton protect the interior from etching by KOH, resulting in low specific surface area (SSA). The advantages of the synergy strategy were evident in the high surface iron content and large SSA of the synthesized magnetic biochar. Further, batch adsorption and recovery experiments were performed on Fe/KOH-C obtained by a simple and low-cost synergistic synthesis strategy, and the results showed that the maximum adsorption capacity of tetracycline was up to 375 mg g−1, with advantages in terms of recovery. Pore filling, electrostatic attraction, π-π interaction, and complexation reaction of the surface functional groups were proved to be the adsorption mechanism of Fe/KOH-C.