Fabrication and characterization of an activated carbon–chitosan–graphene oxide hybrid membrane with hierarchical porosity for the simultaneous adsorptive removal of ciprofloxacin antibiotic and hazardous heavy metals from polluted water systems

Abstract

The development of a new multifunctional hybrid membrane identified as AC/CS/GO-M proved successful for use in water purification. The composite was created by combining commercial activated carbon (AC) derived from coconut shells with chitosan (CS), followed by the incorporation of graphene oxide (GO) nanosheets produced via a modified Hummers' method. The resultant hybrid membrane exhibited a porous architecture characterized by hierarchical micro/mesopores, enhancing its mass transport and adsorption capabilities. A full characterization showed that the components were able to come together and interact successfully: FTIR showed characteristic bands at 3432 cm⁻¹ (–OH/–NH₂ stretching) and 1638 cm⁻¹ (CO vibration), which meant that the interfacial bonds were strong. The XRD patterns indicated semi-crystalline peaks that were similar to those of chitosan and amorphous GO dispersion. SEM analysis revealed a hierarchical porous structure with surface pore diameters ranging from 48 to 215 nm (mean 112 nm), while BET analysis confirmed an average pore diameter of 12.3 nm and a surface area of 238.6 m² g⁻¹ for the AC/CS/GO-M membrane. At pH 6 and 25 °C, the results of batch adsorption studies were impressive, with maximum adsorption capacities (q_max) of 324.5 mg g⁻¹ for Pb²⁺, 298.7 mg g⁻¹ for Cd²⁺, and 156.2 mg g⁻¹ for ciprofloxacin (CIP). The adsorption behavior was in accordance with the pseudo-second-order kinetic model and the Langmuir isotherm (R² > 0.99), suggesting that monolayer chemisorption was mostly attributed to hydrogen bonding, electrostatic interactions, and π–π stacking. Performance declined by less than 8% after five adsorption–desorption cycles in reusability tests. This proved the structure was stable and regenerable. The synergistic combination of AC, CS, and GO created sites with high affinity, quick adsorption, and resistance to bacteria. This made AC/CS/GO a strong simultaneous contender for removing both pharmaceutical contaminants and heavy metals from wastewater treatment systems.