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Updated: Jun 4, 2025
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Quantification of the Potential Impact of Glyphosate-Based Products on Microbiomes
Published on: January 10, 2022
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Glyphosate binding and speciation at the water-goethite interface: A surface complexation model consistent with IR
Bram Geysels1, Tjisse Hiemstra2, Jan E Groenenberg2
1Soil Chemistry and Chemical Soil Quality Group, Wageningen University & Research, PO BOX 47, Wageningen 6700 AA, the Netherlands; INVITE GmbH, Otto-Bayer-Straße 32, D-51061 Cologne, Germany.
Water Research
|December 31, 2024
Summary
Glyphosate (PMG) binding to goethite involves monodentate and bidentate complexes, crucial for understanding its environmental fate and optimizing wastewater removal. This study quantifies PMG adsorption mechanisms on metal oxides.
Area of Science:
- Environmental Chemistry
- Surface Science
- Computational Chemistry
Background:
- Glyphosate (PMG) binding to metal (hydr)oxides influences its environmental availability and mobility.
- Understanding PMG adsorption mechanisms is vital for predicting its fate in aquatic and terrestrial systems and for wastewater treatment.
- A quantitative description of PMG adsorption and surface speciation on metal oxides is currently lacking.
Purpose of the Study:
- To provide mechanistic and quantitative insights into glyphosate (PMG) adsorption and surface speciation on goethite (FeOOH).
- To develop an advanced surface complexation model supported by MO/DFT calculations.
- To improve predictions of PMG fate and transport and optimize its removal by metal (hydr)oxides.
Main Methods:
- Adsorption experiments were conducted over a wide range of pH, solution concentration, and surface loading.
- Advanced surface complexation modeling using the charge distribution approach was employed.
- Molecular orbital/density functional theory (MO/DFT) calculations were used to determine complex geometry, thermochemistry, and IR spectra.
Main Results:
- Mechanistic modeling revealed the formation of both monodentate and bidentate PMG complexes, each with two protonation states.
- Adsorption is primarily (>60%) driven by a bidentate complex, with protonation/deprotonation dependent on pH and loading.
- Monodentate complexes are less prevalent, and the phosphonate group protonates at low pH and high loading.
Conclusions:
- The study provides a new mechanistic and quantitative understanding of PMG binding to goethite.
- The developed model accurately predicts PMG solution concentration and its pH dependency.
- These findings enable improved predictions of PMG fate and transport and offer a framework for optimizing its removal using metal (hydr)oxides.
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