Unraveling synergistic interfacial mechanisms in ibuprofen adsorption on a N-doped magnetic biochar engineered by the FeCl3/urea deep eutectic solvent

Biochar, as a cost-effective and sustainable material, requires surface engineering for efficient removal of emerging contaminants like ibuprofen (IBU). This study demonstrates a facile one-step strategy using a FeCl 3 /urea deep eutectic solvent (DES) as an all-in-one modifier to concurrently introduce magnetization and N-doping during pyrolysis. By optimizing the pyrolysis temperature (500–800 °C) and peanut shell biomass/DES ratio (1:3–1:5), we identified that these parameters critically governed the biochar’s properties including graphitization, nitrogen content, defect density, surface functionalities and porosity. This enabled the synthesis of an N-doped magnetic biochar (PB600 1/5 ) that achieved a high IBU adsorption capacity of 175.75 mg/g, which was attributed to its favorable pore structure, abundant oxygen-containing groups, N functionalities and accessible Fe species. The adsorption followed pseudo-second-order kinetic and the Langmuir isotherm models, driven by mechanisms including pore filling, hydrogen bonding, Fe-complexation and π-related interactions. The biochar also exhibited excellent reusability and anti-interference ability. This work elucidates the synergistic interfacial mechanisms governing IBU adsorption and highlights the FeCl 3 /urea DES as an effective strategy for designing multifunctional biochar for pharmaceutical wastewater remediation.