Atrazine Sorption Kinetics of Two Mexican Agricultural Soils: Effect of Organic Matter

Herbicides are the most widely used agrochemicals to combat weeds. Atrazine is a herbicide used on corn crops. The behavior of atrazine when it enters the soil depends on factors such as adsorption and desorption in the soil, as well as the content and type of clays and organic matter present. The objectives of this research were to characterize two agricultural soils from the State of Mexico, Mexico, treat the natural soils with hydrogen peroxide to eliminate organic matter content, determine the kinetic behavior of atrazine adsorption and evaluate the effect of organic matter on the adsorption of atrazine by the soils. The soil sample with the highest quantity of organic matter showed the greatest adsorption of atrazine. The adsorption capacities were in the following order: soil with organic matter (4.7 and 4.5 mgatz/gsoil) > soils treated with hydrogen peroxide (2.9 and 3.1 mgatz/gsoil) > treated and washed soils (2.2 and 2.7 mgatz/gsoil). Therefore, the soil adsorption capacity for atrazine is related to its organic matter content and chemical composition. The systems reached equilibrium after 6 h of contact. The kinetic model that best describes the kinetic behavior of adsorption was the pseudo-second order model, indicating that the mechanism may involve valence forces in which electrons are shared between the solute and the adsorbent.