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Issue 12, 2017
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A thermodynamical and structural study on the complexation of trivalent lanthanides with a polycarboxylate based concrete superplasticizer

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Abstract

The complexation of trivalent lanthanides with a commercial polycarboxylate based concrete superplasticizer (Glenium® 51) is investigated using different spectroscopic techniques. Time-resolved laser fluorescence spectroscopy (TRLFS) in combination with a charge neutralization model is used to determine temperature dependent conditional stability constants (log β′(T)) for the complexation of Eu(III) with Glenium® 51 in 0.1 mol kg−1 NaCl solution in the temperature range of 20–90 °C. Only one complex species is observed, and log β′(T) (given in kg per mol eq) shows a very slight increase with temperature from 7.5 to 7.9. The related conditional molar reaction enthalpy (ΔrHm) and entropy (ΔrSm) obtained using the Van't Hoff equation show that the complexation reaction is slightly endothermic and entropy driven. The thermodynamic investigations are complemented by structural data for complexes formed with Gd(III) or Tb(III) and Glenium® 51 using extended X-ray absorption fine structure (EXAFS) spectroscopy. The results imply a non-chelate coordination of the trivalent metals through approximately three carboxylic functions of the polycarboxylate comb polymer which are attached predominantly in a bidentate fashion to the lanthanide under the given experimental conditions.

Graphical abstract: A thermodynamical and structural study on the complexation of trivalent lanthanides with a polycarboxylate based concrete superplasticizer

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Publication details

The article was received on 17 Jan 2017, accepted on 24 Feb 2017 and first published on 24 Feb 2017


Article type: Paper
DOI: 10.1039/C7DT00200A
Citation: Dalton Trans., 2017,46, 4093-4100
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    A thermodynamical and structural study on the complexation of trivalent lanthanides with a polycarboxylate based concrete superplasticizer

    D. R. Fröhlich, M. M. Maiwald, F. Taube, J. Plank and P. J. Panak, Dalton Trans., 2017, 46, 4093
    DOI: 10.1039/C7DT00200A

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