Deposition of MnO2 nanoparticles on the magnetic halloysite nanotubes by hydrothermal method for lead(II) removal from aqueous solutions

The magnetic halloysite nanotubes@manganese oxide (MHNTs@MnO2) nanocomposite was synthesized and applied as a novel sorbent for removal of lead(II) ions. The prepared sorbent was characterized by using Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX) and vibrating sample magnetometer (VSM) analysis. Batch mode adsorption studies were performed to evaluate the adsorption kinetics, adsorption isotherms, and selective recognition of MHNTs@MnO2. The equilibrium data was evaluated using Langmuir and Freundlich isotherm. The kinetic data were analyzed using Lagergren pseudo-first-order and pseudo-second order equations. The pseudo-second-order exhibited the best fit for the kinetic studies (R-2 = 0.9999). Equilibrium data fitted by Langmuir adsorption isotherm and the maximum adsorption capacity was calculated as 59.9 mg/g. The adsorption was analyzed thermodynamically, and the results revealed that the removal process was spontaneous and endothermic. In addition, no obvious decrease was observed after up to five adsorption cycles, indicating that the MHNTs@MnO2 adsorbent has a good stability and reusability. It was concluded that MHNTs@MnO2 nanocomposite is an effective material for the removal of Pb(II) from aqueous solutions. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.