Glyphosate is an important and widely used herbicide, its environmental behaviour being of scientific and public interest. Computational models of clay minerals and their interactions with small organic molecules are valuable in studying adsorption processes at an atomistic resolution. We analysed the adsorption process of glyphosate on kaolinite, a clay mineral with a high abundance in several types of soils (e.g., of subtropical or tropical origin), in terms of the adsorption strength. The molecular interactions are characterized by monitoring the occurrence of hydrogen bonds, the orientation of the molecular dipole relative to the interface and the interaction energy. Two different ionic forms of glyphosate were considered: neutral and anionic (−1). It was shown that the main mechanism of the binding of both glyphosate forms to the aluminol surface of kaolinite is through multiple hydrogen bonds. The standard free energy of adsorption of neutral glyphosate from water solution to the basal octahedral surface of kaolinite was computed at −5 kJ mol⁻¹, whereas for the anionic form this quantity amounted to −14 kJ mol⁻¹. Our finding showed that kaolinite has an important contribution to overall adsorption capacity of soils for glyphosate, specifically in its anionic form.

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草甘膦-高岭石表面相互作用。分子动力学研究

草甘膦是一种重要且广泛使用的除草剂，其环境行为具有科学和公共利益。粘土矿物的计算模型及其与有机小分子的相互作用对于以原子分辨率研究吸附过程很有价值。我们根据吸附强度分析了草甘膦在高岭石上的吸附过程，高岭石是一种在几种类型的土壤（例如，亚热带或热带来源）中具有高丰度的粘土矿物。分子相互作用的特点是监测氢键的出现、分子偶极子相对于界面的取向和相互作用能。考虑了两种不同离子形式的草甘膦：中性和阴离子（-1）。结果表明，两种草甘膦形式与高岭石铝醇表面结合的主要机制是通过多个氢键。中性草甘膦从水溶液中吸附到高岭石基底八面体表面的标准自由能计算为 -5 kJ mol^-1，而对于阴离子形式，该量为-14 kJ mol ^-1。我们的发现表明，高岭石对土壤对草甘膦的整体吸附能力有重要贡献，特别是在其阴离子形式中。