Exploring the Adsorption Efficiency of Sulfonated Graphene Oxide for Ciprofloxacin Removal from Aqueous Solution: Insights from Density Functional Theory, Kinetics, Thermodynamics, and Reusability

The pollution of water resources with pharmaceutical substances poses a critical threat to global health and environmental stability. This study demonstrates a highly effective method for removing ciprofloxacin, a broad-spectrum antibiotic and pharmaceutical contaminant, from aqueous solutions using sulfonated graphene oxide (SGO) as an adsorbent. Comprehensive experiments, supported by density functional theory (DFT) analysis, confirm the strong interaction between ciprofloxacin and SGO through microscopy, spectroscopy, and theoretical techniques. The study rigorously evaluates the impacts of adsorption time, medium pH, adsorbent quantity, ciprofloxacin concentration, inorganic cations, and temperature on adsorption performance, providing compelling evidence of SGO's superior performance in mitigating this pressing environmental issue. Results reveal that the adsorption process follows a pseudo-second-order kinetic model and aligns with the Langmuir isotherm, underscoring SGO's high affinity for ciprofloxacin. SGO achieved a significant maximum uptake capacity of 1000.00 μmol/g within 240 min at a low adsorbent dose of 0.2 g/L and optimal pH of 4.0. Thermodynamic assessments indicate that ciprofloxacin adsorption on SGO is both spontaneous and endothermic. Additionally, ciprofloxacin release from antibiotic-loaded SGO was notably high (99.14%) in a solution of 1 M HCl in DMF, and SGO retained over 95.78% of its initial adsorption capacity after five adsorption-desorption cycles, demonstrating its robustness and reusability. These findings strongly position SGO among graphene oxide and their derivatives as a promising and sustainable adsorbent for removing pharmaceutical contaminants, particularly ciprofloxacin, from aqueous solutions. This offers significant potential for advancing water purification technologies in healthcare and environmental applications.