Complexation of uranium(vi) with glyphosate in acidic to basic aqueous solutions

Abstract

The complexation of uranium(VI) with glyphosate (N-(phosphonomethyl)glycine) has been investigated across acidic to basic aqueous solutions using multiple analytical techniques. Eleven uranium(VI)–glyphosate complexes, including 1 : 1, 1 : 2, and 2 : 2 species, were identified under experimental conditions. Thermodynamic parameters—formation constants, as well as enthalpies and entropies of complexation—were determined through potentiometry and calorimetry. The results indicate that the complexation between uranium(VI) and glyphosate (in both L and HL forms) is endothermic and driven by a favorable entropy change. These thermodynamic data, in conjunction with structural information from ³¹P NMR spectroscopy and theoretical validation from DFT calculations, help to identify the coordination modes in the uranium(VI)–glyphosate complexes. In addition, the speciation of glyphosate under environmental conditions, both in the absence and presence of uranium(VI), is discussed.