Comparative characteristics and enhanced removal of tetracycline and ceftriaxone by Fe3O4-lignin and Fe3O4-carbon-based lignin: Mechanism, thermodynamic evaluation, and DFT calculation

•Synthesis of eco-friendly lignin and carbon-based lignin magnetic composites.•Removal of tetracycline (TRC) and ceftriaxone (CEF) by Fe3O4-lignin and Fe3O4-carbon-based lignin.•Electrostatic attraction, hydrophobic, hydrogen bond, and π-π interaction adsorption mechanisms.•Adsorption of TRC was endothermic while that of CEF was exothermic.•DFT calculations and reusability.