Efficient removal of moxifloxacin from aqueous solutions using sulfonated graphene oxide: Adsorption mechanisms, thermodynamics, and reusability

Removing pharmaceutical pollutants from aquatic environments is a significant focus in current environmental research. Graphene-based materials, valued for their stability, are considered effective adsorbents for removing pharmaceuticals from contaminated water. This study explored the adsorptive removal of moxifloxacin onto sulfonated graphene oxide (SGO) from aqueous solutions under various conditions, such as contact time, pH, adsorbent amount, moxifloxacin concentration, presence of inorganic ions, and temperature. The equilibrium adsorption of moxifloxacin onto SGO was examined at different temperatures. The adsorption was confirmed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The maximum adsorption occurred within 240 min at pH 4 with an adsorbent dosage of 0.01 g/50 mL of a 50 mu mol/L moxifloxacin solution. The kinetic data best fit the pseudo-second-order model, rather than the pseudo-first-order or Elovich models. The Langmuir isotherm model described the equilibrium adsorption isotherms, with a maximum adsorption capacity of 1000.00 mu mol/g at 25 degrees C. The values of activation energy (E-a) and thermodynamic parameters (Delta G(double dagger), Delta H-double dagger, Delta S-double dagger, Delta G, Delta H, and Delta S) indicated that the adsorption of moxifloxacin onto SGO is a spontaneous, endothermic physisorption process. A high release of moxifloxacin (99 %) from antibiotic-loaded SGO occurred in 1 mol/L HCl in DMF within 240 min. Even after five adsorption/desorption cycles, SGO maintained over 90 % of its initial adsorption capacity. Therefore, SGO could serve as an effective adsorbent for removing the antibiotic moxifloxacin from aquatic environments.