Adsorption of ciprofloxacin onto engineered biochar derived from floating aquatic weed biomass with isotherm kinetic and interaction mechanism analysis

Amidst growing awareness of One Health and environmental sustainability, contamination of soil and water by various pharmaceutical residues and their role in the dissemination of antimicrobial resistance (AMR) assume significance. In the current investigation, biochar, a promising green material (WH700-1 h) derived from the underexplored aquatic weed water hyacinth, was assessed for its adsorptive capabilities against a widely reported pharmaceutical, ciprofloxacin (CIP). Chemical activation using KOH (yielding KOH-WH700-1 h) and iron salts (yielding Fe-WH700-1 h) enhanced the surface properties of the raw biochar. Adsorption isotherm models revealed both monolayer and heterogeneous surface adsorption, with maximum adsorption capacities of 17.83, 138.50 and 155.04 mg g − 1 for WH700-1 h, Fe-WH700-1 h, and KOH-WH700-1 h, respectively. The iron leaching from the Fe-WH700-1 h biochar was negligible. Kinetic models indicated chemisorption mechanisms for all biochars following the Pseudo Second Order model (R² = 0.99). Brunauer–Emmett–Teller (BET), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM) revealed high surface area (294.189 m 2 g − 1 ), well-developed porosity, diverse functional groups, and heterogeneous surface morphology, all of which contribute to enhanced CIP adsorption. KOH-activated water-hyacinth derived biochar exhibited the highest adsorption capacity in this study, with a q max of 155.04 mg g − 1 . Utilizing water hyacinth-derived biochar as a low-cost, eco-friendly adsorbent for antibiotic removal bridges environmental health and AMR, supports a circular waste valorization approach, and contributes to safer water resources.