Comparison of the adsorption of Zn(II) on alpha- and gamma-MnO2 nanostructures

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Van Phuc Dinh Ngoc Chung Le Ngoc Tuan Nguyen Thien Hoang Ho Van Dong Nguyen


In this report, the adsorption of Zn(II) ion on gamma- and alpha-MnO2 nanostructures was compared. The results showed that the maximum adsorption was obtained at pH = 4.0 for both materials and after 60 minutes for gamma-MnO2 and 80 minutes for alpha-MnO2. Adsorption isotherm models demonstrated that the Langmuir was the best model to describe the adsorption of Zinc(II) on gamma- and alpha-MnO2 because of the highest correlation coefficient (R2), the smallest root mean square error (RMSE), and the nonlinear chi-squared test values. The maximum adsorption capacity of gamma-MnO2 calculated from Langmuir model was 55.23 mg/g, which was roughly double alpha-MnO2. The lower 1/n value from Freundlich model for alpha-MnO2 revealed that it was not as favourable as gamma-MnO2. The heat of the adsorption as well as the mean free energy estimated from Temkin and Dubinin - Radushkevich models to be less than 8 kJ/mol indicated that the adsorption on both materials followed a physical process. Kinetic studies showed that pseudo-second-order model was accurate to describe both materials in three stages.

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DINH, Van Phuc et al. Comparison of the adsorption of Zn(II) on alpha- and gamma-MnO2 nanostructures. Vietnam Journal of Science, Technology and Engineering, [S.l.], v. 59, n. 3, p. 14-19, sep. 2017. ISSN 2525-2461. Available at: <>. Date accessed: 15 dec. 2017.