The removal of lead ions from aqueous solution by using magnetic hydroxypropyl chitosan/oxidized multiwalled carbon nanotubes composites.

Magnetic hydroxypropyl chitosan/oxidized multiwalled carbon nanotubes (MHC/OMCNTs) composites were fabricated and applied as the adsorbent to study the adsorption characteristic of lead ions in aqueous solution. The results of Fourier transform infrared spectrum (FTIR), X-ray powder diffraction (XRD) and scanning electron microscope (SEM) showed that the MHC/OMCNTs composites were synthesized successfully. The effects of the solution pH and the contact time were investigated, indicating that the optimal pH and contact time were pH 5.0 and 120min, respectively. The removal of lead ions was rather quick and the kinetic adsorption can be well described by pseudo-second-order model. The experimental results showed that the Sips model is more suitable than Langmuir, Freundlich and Dubinin-Radushkevich models. Furthermore, the parameters of the adsorption thermodynamic calculated in this research such as free energy (ΔG, -2.304 to -5.078kJmol(-1)), enthalpy (ΔH, 39.03kJmol(-1)) and entropy (ΔS, 138.7Jmol(-1)K(-1)) indicated that the adsorption process was endothermic and spontaneous. Therefore, the results in this research suggest that the MHC/OMCNTs composites are ideal adsorbent for the removal of lead ions in aqueous solution.