Coating carbon nanotubes with crystalline manganese dioxide nanoparticles and their application for lead ions removal from model and real water

Multi-walled carbon nanotubes/manganese oxide (MWCNTs/MnO2) nanocomposite was synthesized, characterized, and used successfully for the removal of lead ions from an aqueous solution and waste water sample. The characterization techniques showed that MWCNTs were coated with 10.2% of the crystalline alpha-MnO2 (w/w percent). The adsorption process was optimized, and the results showed that most of the lead could be removed from a solution with 10 mg MWCNTs/MnO2 nanocomposite, at a pH between 7.0 and 9.0, and within a few min. The adsorption was studied kinetically, and the results revealed that the adsorption of lead ions by a MWCNTs/MnO2 nanocomposite from an aqueous solution could be described well by a pseudo-second-order model and the Elovich model. The mechanism of adsorption showed that the adsorption process was complex and involves a different step, but it was mainly controlled by a liquid film diffusion mechanism. The thermodynamic parameters were calculated, and the adsorption was found to be chemical, spontaneous, and endothermic in nature with positive entropy. The MWCNTs/MnO2 nanocomposite was used for the removal of lead ions from a spiked waste water sample, and the results showed that all the lead ions were removed. (c) 2012 Elsevier B.V. All rights reserved.