Characteristic and CIP antibiotic and DR79 dye of lemongrass biochar derived from distillation waste

Abstract

Lemongrass residue-derived biochar was produced via pyrolysis and evaluated as a sustainable adsorbent for the removal of ciprofloxacin (CIP) and Direct Red 79 (DR79) from aqueous solutions. The physicochemical characteristics of the Biochar was investigated using SEM, BET, EDS, FTIR, and pH_pzc analyses. Pyrolysis at 600 °C generated a carbon-rich mesoporous material with a developed pore network, a specific surface area reaches 79.7 m² g⁻¹, and abundant aromatic structures while retaining oxygen-containing surface functionalities. The biochar exhibited effective adsorption toward DR79 (q_m~44 mg g⁻¹) than CIP (q_m~33 mg g⁻¹). Equilibrium data were best described by the Sips and Freundlich models, indicating adsorption on a heterogeneous surface. Kinetic studies showed that the Elovich model provided the best fit for both pollutants, while intra-particle diffusion played a more significant role in CIP adsorption. DR79 removal was mainly governed by electrostatic attraction, π–π interactions, and pore filling, whereas CIP adsorption involved hydrogen bonding, intra-particle diffusion, and aromatic interactions. These results demonstrate the potential of lemongrass residue biochar as a low-cost, eco-friendly adsorbent for the treating a wide range of organic contaminants.