Glyphosate photodegradation: stoichiometry, kinetic and catalytic effects

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.