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Adsorption of glyphosate on goethite (alpha-FeOOH): Surface complexation modeling combining spectroscopic and adsorption data

Jonsson, Caroline M.; Persson, Per LU ; Sjoberg, Staffan and Loring, John S. (2008) In Environmental Science & Technology 42. p.2464-2469
Abstract
N-(phosphonomethyl)glycine (glyphosate, PMG) is the most widely used herbicide, and its adsorption onto soil minerals plays a significant role in its mobility and rate of degradation. In this work, we present the results of the first serious effort to find a realistic surface complexation model that fits both adsorption and total proton concentration data for PMG on the common soil mineral, goethite. Special attention was focused on making sure that the final model was in good semiquantitative agreement with previously reported X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopic measurements. Electrostatic effects were accounted for using the Basic Stern model, and the charges of the PMG-containing surface... (More)
N-(phosphonomethyl)glycine (glyphosate, PMG) is the most widely used herbicide, and its adsorption onto soil minerals plays a significant role in its mobility and rate of degradation. In this work, we present the results of the first serious effort to find a realistic surface complexation model that fits both adsorption and total proton concentration data for PMG on the common soil mineral, goethite. Special attention was focused on making sure that the final model was in good semiquantitative agreement with previously reported X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopic measurements. Electrostatic effects were accounted for using the Basic Stern model, and the charges of the PMG-containing surface complexes were assumed to be distributed across the O- and beta-planes. The reactions for the protonation of the goethite surface were described using the 1 pK model, We optimized on the intrinsic formation constants and the charge distributions of the complexes, as well as the initial total proton concentration (l = 0.1 M Na(NO3), 25.0 degrees C), and the following model was obtained. FeOH0.5- + H3L reversible arrow FeHL1.5- +H++H2O Log10 beta = 4.70 +/- 0.08, Q(0) = -0.18 +/- 0.02 FeOH0.5- + H3L reversible arrow FeL2.5- + 2H(+) + H2O Log(10) beta = -3.9 +/- 0. 1, Q(0) = -0.7 +/- 0.1 Here, beta is the intrinsic formation constant, Q(0) is the charge at the 0-plane, and the errors are reported as one standard deviation. The charge distributions of the complexes are rationalized by considering intramolecular hydrogen bonding between the protons of the amine group and both the phosphonate and carboxylate groups. (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
in
Environmental Science & Technology
volume
42
pages
2464 - 2469
publisher
The American Chemical Society
external identifiers
  • scopus:41649098527
ISSN
1520-5851
DOI
10.1021/es070966b
language
English
LU publication?
no
id
d8bb8fe5-b578-42c3-8bb3-b70a62f81ccb (old id 4332426)
date added to LUP
2014-03-04 09:47:29
date last changed
2017-10-22 04:20:58
@article{d8bb8fe5-b578-42c3-8bb3-b70a62f81ccb,
  abstract     = {N-(phosphonomethyl)glycine (glyphosate, PMG) is the most widely used herbicide, and its adsorption onto soil minerals plays a significant role in its mobility and rate of degradation. In this work, we present the results of the first serious effort to find a realistic surface complexation model that fits both adsorption and total proton concentration data for PMG on the common soil mineral, goethite. Special attention was focused on making sure that the final model was in good semiquantitative agreement with previously reported X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopic measurements. Electrostatic effects were accounted for using the Basic Stern model, and the charges of the PMG-containing surface complexes were assumed to be distributed across the O- and beta-planes. The reactions for the protonation of the goethite surface were described using the 1 pK model, We optimized on the intrinsic formation constants and the charge distributions of the complexes, as well as the initial total proton concentration (l = 0.1 M Na(NO3), 25.0 degrees C), and the following model was obtained. FeOH0.5- + H3L reversible arrow FeHL1.5- +H++H2O Log10 beta = 4.70 +/- 0.08, Q(0) = -0.18 +/- 0.02 FeOH0.5- + H3L reversible arrow FeL2.5- + 2H(+) + H2O Log(10) beta = -3.9 +/- 0. 1, Q(0) = -0.7 +/- 0.1 Here, beta is the intrinsic formation constant, Q(0) is the charge at the 0-plane, and the errors are reported as one standard deviation. The charge distributions of the complexes are rationalized by considering intramolecular hydrogen bonding between the protons of the amine group and both the phosphonate and carboxylate groups.},
  author       = {Jonsson, Caroline M. and Persson, Per and Sjoberg, Staffan and Loring, John S.},
  issn         = {1520-5851},
  language     = {eng},
  pages        = {2464--2469},
  publisher    = {The American Chemical Society},
  series       = {Environmental Science & Technology},
  title        = {Adsorption of glyphosate on goethite (alpha-FeOOH): Surface complexation modeling combining spectroscopic and adsorption data},
  url          = {http://dx.doi.org/10.1021/es070966b},
  volume       = {42},
  year         = {2008},
}