Unraveling the role of polysaccharide-goethite associations on glyphosate’ adsorption-desorption dynamics and binding mechanisms

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1016/j.jcis.2023.09.141. This is version 2 of this Preprint.

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Behrooz Azimzadeh , Carmen Enid Martínez


Glyphosate retention at environmental interfaces is strongly governed by adsorption and desorption processes. In particular, glyphosate can react with organo-mineral associations (OMAs) in soils, sediments, and aquatic environments. We hypothesize mineral-adsorbed biomacromolecules modulate the extent and rate of glyphosate adsorption and desorption where electrostatic and noncovalent interactions with organo-mineral surfaces are favored.

Here we use in-situ attenuated total reflectance Fourier-transform infrared, X-ray photoelectron spectroscopy, and batch experiments to characterize glyphosate’s adsorption and desorption mechanisms and kinetics at an organo-mineral interface. Model polysaccharide-goethite OMAs are prepared with a range of organic (polysaccharide, PS) surface loadings. Sequential adsorption-desorption studies are conducted by introducing glyphosate and background electrolyte solutions, respectively, to PS-goethite OMAs.

We find the extent of glyphosate adsorption at PS-goethite interfaces was reduced compared to that at the goethite interface. However, increased polysaccharide surface loading resulted in lower relative glyphosate desorption. At the same time, increase PS surface loading yielded slower glyphosate adsorption and desorption kinetics compared to corresponding processes at the goethite interface. We highlight that adsorbed PS promotes the formation of weak noncovalent interactions between glyphosate and PS-goethite OMAs, including the evolution of hydrogen bonds between (i) the amino group of glyphosate and PS and (ii) the phosphonate group of glyphosate and goethite. It is also observed that glyphosate’s phosphonate group preferentially forms inner-sphere monodentate complexes with goethite in PS-goethite whereas bidentate configurations are favored on goethite.




Agriculture, Analytical Chemistry, Biogeochemistry, Environmental Chemistry, Environmental Sciences, Organic Chemistry, Physical Chemistry, Soil Science


glyphosate, pectin, goethite, organo-organic interactions, organo-mineral association, adsorption-desorption kinetics, in-situ ATR-FTIR, hydrogen bonding, pectin, goethite, organo-organic interactions, organo-mineral association, adsorption-desorption kinetics, in-situ ATR-FTIR, hydrogen bonding


Published: 2022-07-23 02:35

Last Updated: 2023-06-09 15:52

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Data will be made available upon acceptance of the manuscript following peer review.