Adsorption of ciprofloxacin on sugarcane bagasse modified with carbon nanotubes: Influence of parameters and sorption mechanism

The increasing occurrence of emergent pollutants in water bodies, such as ciprofloxacin (CIP), underscores the interest in the study of remediation processes. In this context, adsorption emerges as a widely utilized method, employing both economically viable biowaste and highly efficient specialized materials as adsorbents. The main objective of this research was to prepare a composite from sugarcane bagasse (SB) and carbon nanotubes to study its applicability as an adsorbent in the removal of CIP. The composite was prepared by ultrasonic dispersion of alkalinized sugarcane bagasse fibers and oxidized carbon nanotubes. The uptake of CIP was tested by a series of batch experiments with parameter variations. Surface properties were characterized by using SEM, FTIR, and XRD analysis. The composite had a pH_PZC = 6.46 with a proportion of active acid sites of 61.67 % and a phenolic groups predominance. The addition of oxidized carbon nanotubes increased the sorption capacity up to 20 % compared with SB. The study revealed enhanced sorption in the slightly acidic zone at pH values close to pH_PZC. Indeed, mechanisms favorable to sorption were π-π interaction and low CIP solubility. Process kinetics followed pseudo the second order and Weber and Morris models. Finally, experimental data seemed to fit the Langmuir model with a maximum adsorption capacity (q_m) of 16.835 mg·g⁻¹ at 30 °C, without disregarding the Freundlich mechanism since the regression factor R² is similar for both.