Hydrothermal carbonization (HTC) is a promising and powerful technology for manufacturing magnetic biochar with abundant functional groups at relatively low temperature. Herein, K2FeO4-accelerated HTC of kelp was studied to manufacture high-performance magnetic biochar for eliminating tetracycline (TC) in aqueous solution. Nanoscale magnetic iron oxides were generated with abundant oxygen containing groups and porous structures as the HTC was performed at 300 C-degrees. This magnetic biochar displayed 1245.43 mg/g adsorption capacity at 35 C-degrees with 56.48 emu/g saturation magnetization. The adsorption was mostly ascribed to hydrogen bonding/coordination/cation exchange of oxygen functional groups and iron oxides. Moreover, K2FeO4-promoted HTC also exhibited good efficiency and generality for manufacturing potent magnetic biochars from different biowastes for eliminating TC in aqueous solution.
