Adsorption of ciprofloxacin and ofloxacin onto green multi-walled carbon nanotubes in single and multi-component systems: Equilibrium study and machine learning modeling

Abstract

The existence of residual concentrations of pharmaceutical substances in wastewater may impact the local ecosystem and human health, thus, it is required to mitigate the occurrence of these pollutants in effluents. This study performed the equilibrium adsorption in single and multi-component systems for two drugs (ciprofloxacin-CIP and ofloxacin-OFL) onto multi-walled carbon nanotubes, which were functionalized using a green route. Adsorption analyses were performed in batch aqueous systems in single- and multi-component mixtures at 25, 35, and 50 °C. Moreover, multi-component interaction was evaluated in equimolar (1:1) and non-equimolar (1:3 or 3:1) binaries of CIP with OFL. The results indicated that, for all systems evaluated, temperature did not majority influence the adsorption process. Even so, the adsorbed amount of antibiotics was slightly higher at the highest temperature (single-component systems: 0.433 mmol CIP. g−1 and 0.457 mmol OFL. g−1; and multi-component system: 0.958 mmol. CIP.g−1 and 0.872 mmol. OFL.g−1), indicating an endothermic process. The adjustment of the isothermal models indicated that the Sips and the Langmuir-Freundlich models were those that best fit the isotherms for the studied single-component and multi-component systems, respectively. Finally, artificial intelligence techniques were employed as an alternative to adjust the experimental data and revealed greater accuracy in calculating the observed results than traditional equilibrium models.