Green synthesis of Fe–Cu nanoparticles on multiwalled carbon nanotubes for amoxicillin removal from aqueous solution using walnut husk extract

Antibiotics present significant environmental risks due to their persistent and mutagenic properties. This study introduces an innovative method employing an aqueous walnut husk extract to synthesize multiwalled carbon nanotubes (MWCNTs) with enhanced adsorption capabilities. These capabilities are further improved by integrating bimetallic iron–copper (Fe–Cu) nanoparticles onto the MWCNT surface, resulting in MWCNT@Fe–Cu composites. The adsorption capacities for amoxicillin in aqueous solutions were determined to be 613.97 mg/g for MWCNT and 769.23 mg/g for MWCNT@Fe–Cu. Characterization of these materials was carried out using FTIR, BET, TGA, FESEM, EDX, and XRD methods. The specific surface areas measured were 126 m²/g for MWCNT and 229 m²/g for MWCNT@Fe–Cu. Adsorption data adhered to a pseudo-second-order kinetic model and the Langmuir isotherm model provided the best fit. Thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic. The MWCNT@Fe–Cu composite demonstrated remarkable stability after six regeneration cycles, whereas the stability of MWCNT alone diminished over the same period. This enhanced stability is attributed to the Fe–Cu nanoparticles, which prevent agglomeration in aqueous environments. The walnut husk extract is crucial for the formation of carbon nanotubes, offering a sustainable and eco-friendly solution to the problem of antibiotic pollution in water systems.