Gadolinium Complex for the Catch and Release of Phosphate from Water

Sarah M. Harris, Jamie T. Nguyen, Sylvie L. Pailloux, Jarrett P. Mansergh, Mark J. Dresel, Tran B. Swanholm, Tuo Gao, Valérie C. Pierre

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The ability of complexes of hard and labile metal ions with one or more open coordination sites to capture phosphates with high affinity and selectivity directly in water at neutral pH and release them under acidic conditions is evaluated with Gadolinium- 2,2',2"-(((nitrilotris(ethane-2,1-diyl))tris(azanediyl))tris(carbonyl))tris(4-oxo-4H-pyran-3-olate) (Gd-TREN-MAM). This model lanthanide complex has two open coordination sites that, at neutral pH, are filled with water molecules. In water at neutral pH, Gd-TREN-MAM binds phosphate with high affinity (Ka = 1.3 × 104) via the formation of a ternary complex in which one phosphate replaces both inner-sphere water molecules. The formation of this complex is highly pH-dependent; the phosphate is completely released from Gd-TREN-MAM below pH 2. Because the GdIII ion remains complexed by its ligand, even under strong acidic conditions, Gd-TREN-MAM can be used at least 10 times in a pH-based recycling scheme that enables the catch and release of one phosphate per cycle. Gd-TREN-MAM is highly selective for phosphate over other anions of environmental concerns, including HCO3-, HCO2-, CH3CO2-, SO42-, NO3-, NO2-, BrO3-, AsO4-, F-, Cl-, and Br- and, to a lesser extent, ClO3-. The development of such receptors that bind phosphate reversibly in a pH-dependent manner opens the possibility to design catch-and-release systems for the purification of surface waters.

Original languageEnglish (US)
Pages (from-to)4549-4558
Number of pages10
JournalEnvironmental Science and Technology
Issue number8
StatePublished - Apr 18 2017

Bibliographical note

Funding Information:
The authors acknowledge the support of the National Science Foundation provided by INFEWS N/P/H2O:SusChEM CHE- 1610832. Support to J.P.M. from a UROP fellowship from the University of Minnesota and M.J.D. from the North Star Alliance are gratefully acknowledged. We thank Prof. Mauro Botta with help fitting the titration with the PRE equation.

Publisher Copyright:
© 2017 American Chemical Society.

Copyright 2017 Elsevier B.V., All rights reserved.


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