Phosphorus (P) biogeochemical cycle in subsurface environments is primarily mediated by various minerals. However, there is still unknown about the impact of iron (Fe) oxyhydroxides coexisting with clay on the fate of different P species. Here, the interfacial behavior for competitive adsorption of phytate and phosphate on montmorillonite-Fe oxyhydroxide (Mt-amFe) complexes was comprehensively investigated. The nucleation of amorphous Fe oxyhydroxides on montmorillonite contributes to the formation of Mt-amFe complexes and consequently the surface properties of clay are altered. Phytate is preferentially adsorbed on the complexes and the adsorption capacity for phytate is 5.8 times higher than that for P at a mass ratio of 1:1 during the competitive adsorption process. Moreover, during their competition adsorption on Mt-amFe, the interactions between Fe and clay generally tend to decrease the mass ratio of phytate and phosphate in aqueous phases, which is tightly associated with the risk of P contamination. As shown by solid characterization, the adsorption of P species is mainly attributed to inner-sphere complexation. To illustrate the thermodynamic mechanisms for the competitive adsorption effects, dynamic force spectroscopy was applied to quantify the immobilization of different species of P on Mt-amFe complexes, and the results show that phytate is more thermodynamically favorable for the complexation with minerals compared with that of phosphate. These findings can guide the prediction of P loss risk associated with the differences in P species in subsurface environments based on the analysis of mineral surface structures.

中文翻译：

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磷物质在蒙脱石-羟基氧化铁络合物上的竞争吸附机制


地下环境中的磷 （P） 生物地球化学循环主要由各种矿物介导。然而，关于铁 （Fe） 羟基氧化物与粘土共存对不同 P 物种命运的影响，目前尚不清楚。本文全面研究了植酸盐和磷酸盐在蒙脱石-Fe 羟基氧化物 （Mt-amFe） 配合物上竞争性吸附的界面行为。无定形 Fe 羟基氧化物在蒙脱土上的成核有助于 Mt-amFe 络合物的形成，从而改变粘土的表面特性。植酸盐优先吸附在复合物上，在竞争吸附过程中，在质量比为 1：1 的情况下，植酸盐的吸附能力是 P 的 5.8 倍。此外，在它们在 Mt-amFe 上的竞争吸附过程中，Fe 和粘土之间的相互作用通常倾向于降低水相中植酸盐和磷酸盐的质量比，这与 P 污染的风险密切相关。如固体表征所示，P 物质的吸附主要归因于球内络合。为了说明竞争吸附效应的热力学机制，应用动态力谱量化了不同种类的 P 在 Mt-amFe 配合物上的固定化，结果表明，与磷酸盐相比，植酸盐在热力学上更有利于与矿物的络合。这些发现可以指导基于矿物表面结构分析预测与地下环境中 P 种类差异相关的 P 损失风险。