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Issue 5, 2016
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Isothermal titration microcalorimetry to determine the thermodynamics of metal ion removal by magnetic nanoparticle sorbents

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Abstract

Isothermal titration microcalorimetry, a novel approach, was applied to determine key thermodynamic parameters directly for the adsorption of metal ions to a magnetic nanoparticle sorbent (Mag-Ligand), measuring the energy exchange during the binding process. We demonstrate that the interactions are enthalpically driven and energetically favorable, with exothermic binding reactions, giving the selectivity sequence: Cr3+ < Cu2+ < Zn2+ < Ga3+ < Ce3+ < Cd2+ < In3+ < Hg2+ < Pb2+. The sorption kinetic and isothermal studies demonstrated effective and fast removal of nine different metal ions including three rare earths, in competitive and non-competitive conditions across a range of pH and water hardness. Sorption is dominated by the complexation reactions between metal ions and Mag-Ligand and adsorption of metal ions onto Mag-Ligand. Maximum sorption capacity can be predicted based on the thermodynamic data, although kinetics plays a role during competitive sorption. Furthermore, the magnetic behavior of Mag-Ligand results in fast and efficient solid–liquid separation after the sorbent has extracted the metal ions from the contaminated waters, and Mag-Ligand can be regenerated for reuse by a simple acid wash, providing a more sustainable, fast, convenient, and efficient approach for heavy metal remediation.

Graphical abstract: Isothermal titration microcalorimetry to determine the thermodynamics of metal ion removal by magnetic nanoparticle sorbents

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Supplementary files

Article information


Submitted
01 Jul 2016
Accepted
09 Sep 2016
First published
12 Sep 2016

Environ. Sci.: Nano, 2016,3, 1206-1214
Article type
Paper

Isothermal titration microcalorimetry to determine the thermodynamics of metal ion removal by magnetic nanoparticle sorbents

Y. Huang and A. A. Keller, Environ. Sci.: Nano, 2016, 3, 1206
DOI: 10.1039/C6EN00227G

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