Removal of tetracycline from water using rice straw lignin activated carbon magnetized with NiFe₂O₄

This study presents a novel approach for removing tetracycline from water using activated carbon derived from rice straw lignin and magnetized with nickel ferrite nanoparticles. Comprehensive characterization (XRD, BET, EDX, SEM, FTIR) confirmed the successful incorporation of magnetic nanoparticles and the development of a porous structure. Adsorption experiments were conducted across a range of tetracycline concentrations (100–300 mg/L), adsorbent dosages (0.005–0.015 g), pH values (2.1–11), and temperatures (293–313 K). The maximum adsorption capacities reached 322.58 mg/g for pure activated carbon and 714.28 mg/g for the magnetic form at pH 4 and room temperature. Mechanistic studies indicated that the adsorption process was spontaneous, endothermic, and primarily governed by chemisorption, involving hydrogen bonding and π–π interactions between tetracycline molecules and the functional groups on the adsorbent surface. Additionally, the magnetic adsorbent retained 46.72 % of its initial capacity after three reuse cycles, demonstrating good stability and reusability. This work highlights an efficient, sustainable, and magnetically recoverable adsorbent, providing a promising solution for antibiotic removal and agricultural waste valorization in water treatment applications.