Glyphosate and Triton X-100 single-competitive sorption-desorption analysis through kinetic and equilibrium...

Area of Science:

• Environmental Chemistry
• Soil Science
• Agrochemicals

Background:

• Pesticide and surfactant migration in soil poses risks to groundwater quality.
• Understanding competitive sorption-desorption is crucial for assessing leaching potential of agrochemicals.
• Previous models often simplify the complex interactions between co-contaminants in soil.

Purpose of the Study:

• To investigate the sorption-desorption dynamics of glyphosate and Triton X-100 under single and competitive conditions.
• To develop and apply an advanced inverse model (maximum likelihood method) for characterizing these processes.
• To compare equilibrium and kinetic frameworks and evaluate the influence of soil properties and compound interactions.

Main Methods:

• Batch experiments were conducted to gather sorption-desorption data.
• A maximum likelihood algorithm-based inverse model was developed to estimate key sorption-desorption parameters.
• Single and competitive isotherms were integrated into the modeling framework.
• Kinetic analysis was performed to understand the rate-limiting steps.

Main Results:

• Triton X-100 exhibited minimal sorption (max capacity 0.2 mg/gsoil), unaffected by soil type or glyphosate presence.
• Glyphosate sorption (max capacity up to 27 mg/gsoil) increased with soil minerals (up to 45%) and showed higher sorption-desorption ratios under kinetic control.
• Competitive conditions reduced glyphosate sorption by up to 10%, with further reduction at higher Triton X-100 concentrations. Kinetic analysis revealed a rapid initial sorption phase (approx. 70%) followed by slower equilibrium attainment, with Triton X-100 extending this phase and delaying equilibrium.

Conclusions:

• Soil mineralogy significantly enhances glyphosate sorption, influencing its environmental fate.
• The presence of Triton X-100, especially at higher concentrations, negatively impacts glyphosate sorption and prolongs the time to reach equilibrium, increasing leaching risk.
• The developed maximum likelihood method provides a robust approach for quantifying complex sorption-desorption behaviors in environmental matrices.