Adsorption Mechanisms of Glyphosate on Ferrihydrite: Effects of Al Substitution and Aggregation State,Environmental Science & Technology

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Adsorption Mechanisms of Glyphosate on Ferrihydrite: Effects of Al Substitution and Aggregation State
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2023-09-11 , DOI: 10.1021/acs.est.3c04727
Xuewen Li ₁ , Peng Yang ₂ , Wantong Zhao ₁ , Fayang Guo ₁ , Deb P Jaisi ₃ , Shaowei Mi ₁ , Hongju Ma ₄ , Bing Lin ₁ , Xionghan Feng ₁ , Wenfeng Tan ₁ , Xiaoming Wang ₁

Affiliation

Ferrihydrite is one of the most reactive iron (Fe) (oxyhydr)oxides in soils, but the adsorption mechanisms of glyphosate, the most widely used herbicide, on ferrihydrite remain unknown. Here, we determined the adsorption mechanisms of glyphosate on pristine and Al-substituted ferrihydrites with aggregated and dispersed states using macroscopic adsorption experiments, zeta potential, phosphorus K-edge X-ray absorption near-edge structure spectroscopy, in situ attenuated total reflectance Fourier transform infrared spectroscopy coupled with two-dimensional correlation spectroscopy, and multivariate curve resolution analyses. Aggregation of ferrihydrite decreases the glyphosate adsorption capacity. The partial substitution of Al in ferrihydrite inhibits glyphosate adsorption on aggregated ferrihydrite due to the decrease of external specific surface area, while it promotes glyphosate adsorption on dispersed ferrihydrite, which is ascribed to the increase of surface positive charge. Glyphosate predominately forms protonated and deprotonated, depending on the sorption pH, monodentate–mononuclear complexes (MMH₁/MMH₀, 77–90%) on ferrihydrites, besides minor deprotonated bidentate–binuclear complexes (BBH₀, 23–10%). Both Al incorporation and a low pH favor the formation of the BB complex. The adsorbed glyphosate preferentially forms the MM complex on ferrihydrite and preferentially bonds with the Al–OH sites on Al-substituted ferrihydrite. These new insights are expected to be useful in predicting the environmental fate of glyphosate in ferrihydrite-rich environments.

中文翻译：

草甘膦在水铁矿上的吸附机制：铝取代和聚集状态的影响

水铁矿是土壤中最具活性的铁(Fe)(羟基)氧化物之一，但最广泛使用的除草剂草甘膦在水铁矿上的吸附机制仍不清楚。在这里，我们利用宏观吸附实验、zeta电位、磷K边X射线吸收近边结构光谱、原位衰减全反射傅里叶变换确定了草甘膦在聚集态和分散态的原始水铁矿和铝取代水铁矿上的吸附机制。红外光谱与二维相关光谱以及多元曲线分辨率分析相结合。水铁矿的聚集降低了草甘膦的吸附能力。水铁矿中Al的部分取代由于外部比表面积的减小而抑制了聚集的水铁矿上的草甘膦吸附，而由于表面正电荷的增加而促进了分散的水铁矿上的草甘膦吸附。草甘膦主要形成质子化和去质子化，取决于吸附 pH，在水铁矿上形成单齿-单核复合物 (MMH ₁ /MMH ₀ , 77-90%)，此外还有少量去质子化的双齿-双核复合物 (BBH ₀ , 23-10%)。 Al 的掺入和低 pH 值都有利于 BB 络合物的形成。吸附的草甘膦优先在水铁矿上形成MM络合物，并优先与铝取代的水铁矿上的Al-OH位点结合。这些新见解预计将有助于预测草甘膦在富含水铁矿的环境中的环境命运。

更新日期：2023-09-11

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