One-step synthesis of 1,6-hexanediamine modified magnetic chitosan microspheres for fast and efficient removal of toxic hexavalent chromium

Rui Yue,Xiaodan Zhang,Ping Feng,Yuming Huang,Qiumeng Chen,Siqi Li

doi:10.1038/s41598-018-29499-z

Rui Yue, Xiaodan Zhang + Show 4 more

Open Access

https://doi.org/10.1038/s41598-018-29499-z

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Journal: Scientific Reports	Publication Date: Jul 23, 2018
Citations: 22	License type: open-access

Affiliation: Southwest University

Abstract

Here, we reported a novel one-step hydrothermal route for the facile synthesis of 1,6-hexanediamine functionalized magnetic chitosan microspheres (AF-MCTS), which were characterized by TEM, FT-IR and XPS to look into its morphology, surface functional groups, and adsorption mechanism of Cr(VI) from the aqueous solution. Cr(VI) adsorption on AF-MCTS as a function of contact time, Cr(VI) concentration, pH, and ionic strength was investigated. The adsorption process follows the Langmuir isotherm model and pseudo-second-order kinetic model. The AF-MCTS exhibited high performance for Cr(VI) removal with very fast adsorption rate (reaching equilibrium within 5 min) and high adsorption capacity (208.33 mg/g), which was 1.1 to 12 times that of other chitosan-based adsorbents. Cr(VI) adsorption onto AF-MCTS was an endothermic and spontaneous process. The recovery and reuse of AF-MCTS was demonstrated 11 times without obvious decrease in adsorption capacity. Mechanism study suggested that –OH rather than –NH2 groups in AF-MCTS were the electron donors for reducing Cr(VI) to Cr3+. Consumption or addition of H+ could trigger the reversible supramolecular coordination between Cr3+ and chitosan. Given the easy preparation, low cost, and remarkable performance, AF-MCTS composite is expected to show promising potential for the practical application in removing toxic Cr(VI) from aqueous media.

Highlights

Chromium mainly comes from a variety of industry activities[1]
The energy dispersive spectroscopy (EDS) spectra and atomic ratio of corresponding elements in amino-functionalized magnetic chitosan microspheres (AF-magnetic chitosan (MCTS)) composite are shown in Fig. S1 in Supporting Information
We demonstrated the development of AF-MCTS for rapid and efficient elimination of toxic Cr(VI) from aqueous solution through adsorption

Summary

Results and Discussion

It is clear that addition of NaCl leads to a big decline in zeta potential value of AF-MCTS, suggesting that addition of Cl− ions results in the decrease in the available surface sites for hexavalent chromium adsorption This is because the occupied sites decrease surface charge of AF-MCTS adsorbent, leading to increase in the electrostatic repulsion between AF-MCTS surface and Cr(VI) anions. A probable mechanism for the removal of Cr(VI) with AF-MCTS adsorbent is proposed, and it contains two main steps (Fig. 7): (1) protonation of the -NH and -NH2 groups in chitosan chains into -NH2+/-NH3+ at pH 3.0 media, leading to Cr(VI) diffusion from aqueous solution to positive charged AF-MCTS adsorbent through electrostatic interaction; (2) partial hexavalent chromium reducing to Cr3+ by -OH groups onto AF-MCTS, and the formed Cr3+ was re-adsorbed by the AF-MCTS through supramolecular coordination

Conclusion

Author Contributions

Additional Information