Unveiling synergistic effect of potassium permanganate and potassium ferrate to manufacture magnetic biochar by low-temperature pyrolysis for efficient adsorption of tetracycline and copper

Pyrolysis impregnation of magnetic iron is a promising strategy for preparation of magnetic biochar, but high temperature is usually required to produce magnetic iron species. Herein, a novel co-oxidative pyrolysis using potassium permanganate and potassium ferrate was explored for synthesis of magnetic biochar at 250–400 °C. Additionally, the magnetic biochar was applied to remove tetracycline and copper(II) from aqueous solution. This co-oxidative pyrolysis successfully impregnated magnetite, zero-valent iron, and manganese ferrite into carbon matrix with manganese oxides at 250 °C. Meanwhile, porous structures were created, accompanying by abundant oxygen groups. This magnetic biochar displayed 720.7 and 267.9 mg/g adsorption capacities toward tetracycline and copper(II) at 35 °C correspondingly, with 21.79 emu/g saturation magnetization. High adsorption capability was still achieved in real water matrices, showing great potential of the magnetic biochar for wastewater treatment in industry. The adsorption could be primarily contributed to hydrogen bond/complexation/π-π interaction/pore filling for tetracycline and cation exchange/complexation/electrostatic interaction/pore filling for copper(II). The success in fabrication of highly adsorptive magnetic biochar by potassium permanganate and potassium ferrate co-oxidative pyrolysis at low temperature, demonstrating oxidative magnetization was a promising technology for synthesis of high performance magnetic biochar with low energy consumption.