Utilization of diatomite/chitosan–Fe (III) composite for the removal of anionic azo dyes from wastewater: Equilibrium, kinetics and thermodynamics

[Display omitted] •Fe(III)/Cs@Dia was confirmed as an excellent absorbent for anionic azo dyes.•Pseudo-second-order kinetic model showed a better-fit to the experimental data.•The equilibrium data fitted better with the Langmuir model.•Adsorption of 2GL dye onto adsorbent was exothermic in nature.•A...

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Bibliographic Details
Published in:Colloids and surfaces. A, Physicochemical and engineering aspects Physicochemical and engineering aspects, 2015-03, Vol.468, p.129-139
Main Authors: Zheng, Liuchun, Wang, Chenggang, Shu, Yuehong, Yan, Xiaomin, Li, Laisheng
Format: Article
Language:English
Subjects:
Adsorption
Adsorption mechanism
Anionic azo dye
Azo dyes
Composite
Diatomite
Dyes
Isotherm
Isotherms
Kinetic
Surface chemistry
Thermodynamics
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Summary:[Display omitted] •Fe(III)/Cs@Dia was confirmed as an excellent absorbent for anionic azo dyes.•Pseudo-second-order kinetic model showed a better-fit to the experimental data.•The equilibrium data fitted better with the Langmuir model.•Adsorption of 2GL dye onto adsorbent was exothermic in nature.•Adsorption mechanisms mainly involved electrostatic interaction and complexation. A novel diatomite/chitosan–Fe(III) composite (Fe(III)/Cs@Dia) was synthesized successfully to use as an adsorbent for the removal of anionic azo dye. The composite was further characterized by SEM, FTIR, XPS, and C13/Si29NMR, and then the adsorption batch experiments were carried out as a function of initial dye concentrations, pH values, contact time and temperatures to determine the adsorption capacities of Fe(III)/Cs@Dia. Compared with several typical isotherm models, the adsorption isotherms were all best-fitted by the Langmuir model, with a maximal 2GL dye uptake of 1250mgg−1 at pH 6 and 298K. In addition, kinetic studies followed the pseudo-second-order model and thermodynamic studies revealed that the uptake was exothermic in nature. The adsorption mechanisms were proposed with observation that electrostatic interaction and complexation played the key roles in adsorption process. Moreover, the composite also showed favorable adsorption properties for other four anionic azo dyes (direct yellow R, congo red, methyl orange and direct red 23).
ISSN:0927-7757
1873-4359
DOI:10.1016/j.colsurfa.2014.12.015