The growing occurrence of antibiotics in aquatic environments has emerged as a notable environmental issue given their potential detrimental impacts on ecosystems and the well-being of individuals. Therefore, there is a pressing need to develop effective strategies for removing antibiotics from wastewater. Herein, PW12/Fe3O4/biochar nanocomposite as a highly efficient adsorbent was synthesized to remove metronidazole (MNZ) antibiotic from wastewater through a sustainable and environmentally friendly approach. Simple surface modifications, such as chemical and physical modification with acid and base, as well as adding polyoxometalate were employed to enhance the adsorption of MNZ. The physical and chemical characteristics of the adsorbent were extensively analyzed using several techniques as follows, Fourier transform infrared (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray (EDX), Brunauer-Emmett-Teller (BET), and transmission electron microscopy (TEM). Experimental results demonstrated a significant increase in the efficacy of MNZ removal when the adsorbent surface was modified with polyoxometalate (H3PW12O40) compared to magnetic biochar (MBC). This improvement favors the pore-filling mechanism, electrostatic, H-bonds, and π-π interactions. To optimize the operating parameters for MNZ removal, response surface methodology (RSM) was employed using Design Expert software, considering the pH of a solution, initial pollutant concentration, adsorbent amount, and contact time. The results revealed that when the conditions were ideal (pH ∼1, initial concentration of MNZ at 5 mg/L, adsorbent amount of 0.6 g/L, and contact time of 60 minutes), the removal efficiency and the adsorption capacity reached 94.28 % and 78.45 mg/g, respectively. The analysis of isotherm and kinetic experiments revealed that the adsorption mechanism followed the Freundlich isotherm and pseudo-second order kinetic models, respectively. Furthermore, the adsorbent demonstrated excellent efficiency and reusability, with a removal efficiency of over 90% even after four cycles, highlighting its potential and economic viability as an adsorbent for metronidazole removal.

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