Probing the potential of ureasil-poly(ethylene oxide) as a glyphosate scavenger in aqueous milieu: force-field parameterization and MD simulations

Abstract

The intensive use of glyphosate in conventional agriculture and its high solubility in water have led to contamination of aqueous systems worldwide. The removal of organic pollutants from water by hybrid materials like ureasil-poly(ethylene oxide) U-PEO800 is gaining attention due to its efficiency, robustness, and matrix regeneration possibilities, leading to successive applications. A new application for the U-PEO800 polymer as a glyphosate scavenger in aqueous medium is proposed and investigated theoretically by molecular dynamics (MD) simulations, providing new insights into the sorption process. The quality of MD simulations is highly dependent on the nature of the applied force field. For that reason, it is reported here, for the first time, the parameterization of the U-PEO800 polymer fragment containing Si atoms. The parameterization procedure, containing bonded terms compatible with GAFF for the U-PEO800 fragment, has employed rigorous ab initio methods. The behavior of U-PEO800 in water was then investigated by MD simulations using the new parameters obtained, and the aggregation process between polymer molecules has been observed. The polymer was able to interact with the pesticide, even under different pH conditions. When the pesticide and polymer have neutral chains, the interaction is mostly through hydrogen bonds between the PEO monomer unit and the pesticide hydrogen bond donor groups. On the other hand, when considering the structures at different pHs, the electrostatic component of the interaction is predominant, since the polymer has a total charge +4 e and the pesticide was evaluated with net charges −1 and −2 e. Our findings reveal that U-PEO800 proved to be a very promising sorbent for glyphosate.