Cucurbit[7]uril-modified magnetically recyclable carbon nanotubes for efficient removal of Pb (II) from aqueous solutions

In this work, a magnetic material based on carbon nanotubes (CB[7]@Fe3O4/MWCNT -NH2) was fabricated by combining amino carbon nanotubes, Fe3O4, and cucurbit[7]uril (CB[7]). This material can effectively remove Pb (II) in water and can be recovered in a short time by magnetic adsorption. The structure of the magnetic material was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR), vibrating sample magnetometer (VSM), and BET specific surface area. The effect of CB[7]@Fe3O4/MWCNT-NH2 on the adsorption performance of Pb (II) under different temperatures, pH, and time conditions were investigated. The experimental data showed that the adsorbent's Pb (II) adsorption process had an excellent correlation with the Langmuir isotherm model and the pseudo-second-order kinetic model. The maximum adsorption capacity of the adsorbent material at 20 °C was 245.6 mg g−1, which was approximately 3.27 times higher than that of the non-introduced CB[7] magnetic adsorbent. These results demonstrated the excellent Pb (II) adsorption capabilities of the developed adsorbent. Furthermore, the thermodynamic analysis revealed that the adsorption process was exothermic and spontaneous. Additionally, CB[7]@Fe3O4/MWCNT-NH2 retained 82% of its initial capacity even after undergoing 5 repeated cycles. In conclusion, CB[7]@Fe3O4/MWCNT-NH2 was a promising green and environmentally friendly adsorbent for the removal of Pb (II) in wastewater.