Study of ciprofloxacin adsorption and regeneration of activated carbon prepared from Enteromorpha prolifera impregnated with H3PO4 and sodium benzenesulfonate

- The addition of sodium benzenesulfonate in activation process increased the carbon's surface functional groups.
- Initial pH had significant impact on ciprofloxacin uptake onto the four carbons.
- Adsorption capacity for ciprofloxacin by modified activated carbon exceeded that of original one.
- Adsorption mechanisms: cation exchange and electrostatic attraction.

Activated carbons were derived from Enteromorpha prolifera immersed in H3PO4 solution or the H3PO4 solution mixed with sodium benzenesulfonate (SBS), producing AC and AC-SBS. NaOH solution was employed in regeneration of ciprofloxacin (CIP)-loaded AC and AC-SBS to obtain RAC and RAC-SBS. The properties of the original and regenerated activated carbons were characterized by thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), N2 adsorption/desorption isotherms and Fourier transform infrared spectroscopy (FTIR). Batched adsorption studies were carried out to compare CIP adsorption behaviors of the four carbons. The results suggested that the four samples exhibited higher proportions of mesopores and similar functional groups. Although AC displayed much higher specific surface area (SBET) (1045.79 m2/g) than AC-SBS (738.03 m2/g), its CIP adsorption capacity was much less than AC-SBS. The maximum adsorption capacity for AC, AC-SBS, RAC and RAC-SBS were found to be 250 mg/g, 286 mg/g, 233 mg/g and 256 mg/g, respectively, with the isotherms adhering to Langmuir isotherm model. The electrostatic attraction and cation exchange between CIP and the four carbons were the dominant adsorption mechanisms. Moreover, the thermodynamic parameters represented that the adsorption process had been confirmed to be a spontaneous and endothermic reaction.