Title: Glyphosate photodegradation: stoichiometry, kinetic and catalytic effects

Authors: María Alcira Trinelli; Cecilia G. Cantera; María Mar Areco; María Dos Santos Afonso

Addresses: Departamento de Química Inorgánica, Analítica y Química Física, Universidad de Buenos Aires, Buenos Aires, Argentina; CONICET-Universidad de Buenos Aires, Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), Ciudad Universitaria Pabellón II 3er Piso, Intendente Guiraldes 2160 (C1428EHA), Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, (C1425FQB), Buenos Aires, Argentina ' CONICET-Universidad de Buenos Aires, Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), Ciudad Universitaria Pabellón II 3er Piso, Intendente Guiraldes 2160 (C1428EHA), Buenos Aires, Argentina ' CONICET-Universidad de Buenos Aires, Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), Ciudad Universitaria Pabellón II 3er Piso, Intendente Guiraldes 2160 (C1428EHA), Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, (C1425FQB), Buenos Aires, Argentina ' Departamento de Química Inorgánica, Analítica y Química Física, Universidad de Buenos Aires, Buenos Aires, Argentina; CONICET-Universidad de Buenos Aires, Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), Ciudad Universitaria Pabellón II 3er Piso, Intendente Guiraldes 2160 (C1428EHA), Buenos Aires, Argentina

Abstract: Photodegradation of glyphosate (PMG) in aqueous solution by the action of UV-light and the catalytic effect of copper and copper-alga Ulva lactuca is described. The photodegradation kinetic reaction of PMG can be explained using a first-order kinetic model, with a mean rate constant of k = (0.04 ± 0.01) h^-1 and a mean half-life (τ) = (17 ± 4) h. The quantum yield (φ) obtained for the photochemical decomposition of PMG was (4.8 ± 0.1) 10^-4 mol Einstein^-1. The resulting photodegradation by-products obtained were acetate, aminomethylphosphonic acid (AMPA), phosphate, sarcosine and to a lesser extent nitrate. The rate of PMG degradation is increased by the presence of copper and Cu-alga Ulva lactuca in the reaction media. The present work represents a new understanding on the photodegradation of the herbicide glyphosate and the results obtained may contribute to the development of new remediation technologies.

Keywords: glyphosate; photodegradation; stoichiometry; copper; Ulva lactuca; kinetic model; catalysis; UV-light; by-products of photodegradation; acetate; AMPA; aminomethylphosphonic acid; phosphate; sarcosine; nitrate.

DOI: 10.1504/IJENVH.2019.108663

International Journal of Environment and Health, 2019 Vol.9 No.4, pp.306 - 326

Received: 20 Apr 2019
Accepted: 02 Oct 2019
Published online: 24 Jul 2020 *

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