Ma Jie, Li Jinbo, Weng Liping, Ouyang Xiaoxue, Chen Yali, Li Yongtao
Key Laboratory for Environmental Factors Control of Agro-Product Quality Safety, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China.
Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China.
Environ Sci Technol. 2023 Mar 14;57(10):4219-4230. doi: 10.1021/acs.est.2c09670. Epub 2023 Feb 27.
The transport of ferrihydrite colloid (FHC) through porous media is influenced by anions (e.g., PO) and cations (e.g., Ca) in the aqueous environment. This study investigated the cotransport of FHC with P and P/Ca in saturated sand columns. The results showed that P adsorption enhanced FHC transport, whereas Ca loaded onto P-FHC retarded FHC transport. Phosphate adsorption provided a negative potential on the FHC, while Ca added to P-FHC led to electrostatic screening, compression of the electric double layer, and formation of Ca(PO)OH followed by heteroaggregation at pH ≥ 6.0. The monodentate and bidentate P surface complexes coexisted, and Ca mainly formed a ternary complex with bidentate P (≡(FeO)POCa). The unprotonation bidentate P at the Stern 1-plane had a considerable negative potential at the Van der Waals molecular surface. Extending the potential effect to the outer layer of FHC, the potential at the Stern 2-plane and zeta potential exhibited a corresponding change, resulting in a change in FHC mobility, which was validated by comparison of experimental results, DFT calculations, and CD-MUSIC models. Our results highlighted the influence of P and Ca on FHC transport and elucidated their interaction mechanisms based on quantum chemistry and colloidal chemical interface reactions.
水铁矿胶体（FHC）在多孔介质中的运移受水环境中阴离子（如PO）和阳离子（如Ca）的影响。本研究考察了FHC与P以及P/Ca在饱和砂柱中的共运移情况。结果表明，P的吸附促进了FHC的运移，而负载在P-FHC上的Ca则阻碍了FHC的运移。磷酸盐吸附在FHC上产生负电位，而添加到P-FHC中的Ca导致静电屏蔽、双电层压缩，并在pH≥6.0时形成Ca(PO)OH，随后发生异质凝聚。单齿和双齿P表面络合物共存，Ca主要与双齿P形成三元络合物（≡(FeO)POCa）。在斯特恩1平面上未质子化的双齿P在范德华分子表面具有相当大的负电位。将电位效应扩展到FHC外层，斯特恩2平面的电位和ζ电位呈现相应变化，导致FHC迁移率改变，通过实验结果、密度泛函理论（DFT）计算和CD-MUSIC模型的比较得到验证。我们的结果突出了P和Ca对FHC运移的影响，并基于量子化学和胶体化学界面反应阐明了它们的相互作用机制。
