Glyphosate and Triton X-100 single-competitive sorption–desorption analysis through kinetic and equilibrium frameworks utilizing maximum likelihood method

This study investigates the sorption and desorption dynamics of glyphosate and Triton X-100 under both single and competitive conditions within equilibrium and kinetic frameworks. Understanding competitive sorption-desorption, determining the leaching potential, is critical in agricultural contexts where pesticides and surfactants can migrate through soil and contaminate groundwater. This study develops an advanced inverse model based on a maximum likelihood algorithm to characterize sorption-desorption, integrating single and competitive isotherms to estimate key parameters from batch experiments. The study further explores the impacts of compound competition, concentration ratios, and soil properties on sorption-desorption processes, while providing a quantitative comparison between equilibrium and kinetic frameworks. Results indicate that Triton X-100 exhibits minimal sorption with maximum sorption capacity of 0.2 mg/g_soil, which sorption characteristics remain nearly identical regardless of soil composition or the presence of glyphosate. For glyphosate, with a maximum sorption capacity up to 27 mg/gsoil, the presence of minerals such as albite, muscovite, kaolinite, and illite can increase sorption by up to 45%, resulting in higher sorption to desorption ratio under kinetic conditions and achieving equilibrium in a shorter timeframe. Moreover, the MLM results indicate that competitive conditions reduce glyphosate sorption by up to 10%, with a further 10% decrease observed as the Triton X-100 concentration increases from 0.5 to 2%. Kinetic analysis shows that glyphosate sorption-desorption, in both single and competitive conditions, includes an initial rapid sorption phase where approximately 70% of total sorption occurs with minimal desorption, followed by a slower phase as the system nears equilibrium. The presence of Triton X-100, especially at higher concentrations, extends the rapid sorption phase and delays equilibrium, altering glyphosate's sorption pattern. Moreover, peak sorption-desorption rates occur within the first 100 min in single-sorption scenarios, while the presence of Triton X-100 slows the sorption rate, spreading it up to 300 min.