Imidacloprid removal by modified graphitic biochar with Fe/Zn bimetallic oxides

Coping with the critical challenge of imidacloprid (IMI) contamination in sewage treatment and farmland drainage purification, this study presents a pioneering development of an advanced modified graphitic white melon seed shells biochar (Fe/Zn@WBC). The Fe/Zn@WBC demonstrates a substantial enhancement in adsorption efficiency for IMI, achieving a remarkable removal rate of 87.69% within 30 min and a significantly higher initial adsorption rate parameter h = 4.176 mg g^-1·min^-1. This significant improvement outperforms WBC (12.22%, h = 0.115 mg g^-1·min^-1) and highlights the influence of optimized adsorption conditions at 900 °C and the graphitization degree resulting from Fe/Zn bimetallic oxide modification. Characterization analysis and batch sorption experiments including kinetics, isotherms, thermodynamics and pH factors illustrate that chemical adsorption is the main type of adsorption mechanism responsible for this superior ability to remove IMI through pore filling, hydrogen bonding, hydrophobic interaction, electrostatics interaction, π-π interactions as well as complexation processes. Furthermore, we demonstrate exceptional stability of Fe/Zn@WBC across a broad pH range (pH = 3-11), co-existing ions presence along with humic acid under various real water conditions while maintaining high removal efficiency. This study presents an advanced biochar adsorbent, Fe/Zn@WBC, with efficient adsorption capacity and easy preparation. Through three regeneration cycles via pyrolysis method, it demonstrates excellent pyrolysis regeneration capabilities with an average removal efficiency of 92.02%. The magnetic properties enable rapid separation facilitated by magnetic analysis. By elucidating the efficacy and mechanistic foundations of Fe/Zn@WBC, this research significantly contributes to the field of environmental remediation by providing a scalable solution for IMI removal and enhancing scientific understanding of bimetallic oxides-hydrophilic organic pollutant interactions.