Evaluation of synthesized MWCNTs-COO@Fe₃O₄ nanocomposite based on laser-assisted method for highly-efficient clean water

In this study, the surface of MWCNTs was treated with acid by adding a carboxyl group to be ready to load nanostructured materials on their surface in a novel way. The femtosecond laser ablation process was used for decorating magnetic nanoparticles (Fe₃O₄) on the functionalized carbon nanotubes (MWCNTs-COOH) to form the MWCNTs-COO@Fe₃O₄ nanocomposite structure to be used for the heavy metal removal of Pb(II). Different techniques have all been used to identify the functionality groups that are present on the MWCNTs. Raman spectroscopy showed the decrease of G band when Fe₃O₄ nanoparticles embedded MWCNTs-COOH, indicating a greater degree of defect in MWCNTs. VSM showed the magnetic characteristic properties of the composite. XRD showed the reduction of MWCNTs diffraction peaks after embedding with iron oxide, explained the partial full coverage of the MWCNTs surface by the Fe₃O₄ nanoparticles. FT-IR showed the composite exhibit a peak at 579 cm⁻¹, which is brought on by the Fe–O stretching vibrational modes. Zeta potential showed the surface of the MWCNTs-COO@Fe₃O₄ had a more positive charge under neutral pH compared with that of MWCNTs. TGA showed the weight loss of MWCNTs-COO@Fe₃O₄ was greater than that of MWCNTs, confirming the interaction of some Fe₃O₄ on MWCNTs-COOH. Also, tested pH, contact time, initial Pb (II) concentration, and adsorbent mass were carried to improve Pb (II) ion adsorption on the nanocomposite. The optimal removal effectiveness of Pb (II) on the MWCNTs-COO@Fe₃O₄ nanocomposite is attained when the experiment is conducted at a pH of 6, with a contact time of 10 min, an initial concentration of 100 mg/L, and under alkaline conditions. Pb (II) ions were adsorbing using a pseudo-second-order equation to reflect their chemical adsorption, with a rate constant of (k₂ = 0.00446 g mg⁻¹ min⁻¹). The highest adsorption capacity obtained was 66.85 mg g⁻¹. MWCNTs-COO@Fe₃O₄ nanocomposite efficiently collected Pb (II) utilizing green and easy to use method to protect public health.