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4270083 
Journal Article 
Insight into adsorption mechanism of lead(II) from aqueous solution by chitosan loaded MnO2 nanoparticles 
Van-Phuc Dinh; Ngoc-Chung Le; Anh Tuyen, L; Quang Hung, N; Van-Dong Nguyen; Ngoc-Tuan Nguyen 
2018 
1 
Materials Chemistry and Physics
ISSN: 0254-0584
EISSN: 1879-3312 
ELSEVIER SCIENCE SA 
LAUSANNE 
207 
294-302 
WOS:000425561000039 
Manganese dioxide nanoparticles are loaded onto the surface of chitosan (CS) in order to enhance their adsorption properties. Various theoretical models and spectroscopic analytical methods are used to investigate the equilibrium isotherm, kinetics, and mechanisms of the removal of lead(II) from the aqueous solution. The kinetic studies based on a pseudo-second-order model show that the uptake of lead(II) occurs via three stages depending on the reaction time. The experimental data are fitted using four nonlinear isotherm models, namely the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models. The results obtained within the Langmuir model gave the highest R-2, the smallest root-mean squared error (RMSE), and the best nonlinear chi-square test (chi(2)) values, indicating that this model is the most appropriate approach for describing the adsorption of lead(II) onto the MnO2/CS nanomaterials. It is also found that the maximum monolayer adsorption capacity is 126.1 mgig, which is higher than most of the values obtained from other materials. In addition, the results of the heat of the sorption process and the mean free energy calculated from the Fourier transform infrared spectroscopy (FTIR) suggested that the adsorption indeed follows a physical process. By using the Positron Lifetime Spectroscopy, which is used for the first time to investigate the "ions-holes" mechanism of the removal of lead(H) by CS loaded MnO2 nanoparticles, we found that the "ions-holes" mechanism in fact occurs at the micropores of MnO2 crystals in the MnO2/CS nanomaterials. This result is significant as it will be a reference for the use of the spectroscopic analytical methods for investigating the adsorption mechanism. (C) 2017 Elsevier B.V. All rights reserved. 
Chitosan loaded MnO2 (MnO2/CS); Lead(II); Adsorbed mechanisms; Positron lifetime spectroscopy