Trace metals (e.g. Ni, Zn) leached from industrial and agricultural processes are often simultaneously present in contaminated soils and sediments. Their mobility, bioavailability, and ecotoxicity are affected by sorption and cosorption at mineral/solution interfaces. Cosorption of trace metals has been investigated at the macroscopic level, but there is not a clear understanding of the molecular-scale cosorption processes due to lack of spectroscopic information. In this study, Ni and Zn cosorption to aluminum oxides (γ-Al2O3) in binary-sorbate systems were compared to their sorption in single-sorbate systems as a function of pH using both macroscopic batch experiments and synchrotron-based X-ray absorption fine structure spectroscopy. At pH 6.0, Ni and Zn were sorbed as inner-sphere surface complexes and competed for the limited number of reactive sites on γ-Al2O3. In binary-sorbate systems, Ni had no effect on Zn sorption, owning to its lower affinity for the metal oxide surface. In contrast, Zn had a higher affinity for the metal oxide surface and reduced Ni sorption. At pH 7.5, Ni and Zn were sorbed as mixed-metal surface precipitates, including Ni-Al layered double hydroxides (LDHs), Zn-Al LDHs, and likely Ni-Zn-Al layered triple/ternary hydroxides. Additionally, at pH 7.5, Ni and Zn do not exhibit competitive sorption effects in the binary system. Taken together, these results indicated that pH critically influenced the reaction products, and provides a crucial scientific basis to understand the potential mobility, bioavailability, and ecotoxicity of Ni and Zn in natural and contaminated geochemical environments.

中文翻译：

---

氧化铝/水界面上镍和锌的竞争性吸附：XAFS研究。

从工业和农业过程中浸出的痕量金属（例如，镍，锌）通常同时存在于受污染的土壤和沉积物中。它们的流动性，生物利用度和生态毒性受矿物/溶液界面处的吸附和共吸附作用的影响。痕量金属的吸附已在宏观层面进行了研究，但由于缺乏光谱信息，因此对分子尺度的吸附过程尚无清晰的了解。在这项研究中，使用宏观间歇实验和基于同步加速器的X射线吸收法，比较了二元吸附物体系中Ni和Zn对氧化铝（γ-Al2O3）的共吸附与单吸附物体系中随pH值的吸附的比较。结构光谱学。在pH 6.0下，Ni和Zn作为内球表面复合物被吸附，并竞争γ-Al2O3上有限数量的反应位。在二元山梨酸盐体系中，Ni对锌的吸附没有影响，因为它对金属氧化物表面的亲和力较低。相反，Zn对金属氧化物表面具有更高的亲和力，并且减少了Ni的吸附。在pH 7.5下，Ni和Zn作为混合金属表面沉淀物被吸附，包括Ni-Al层状双氢氧化物（LDHs），Zn-Al LDHs和可能的Ni-Zn-Al层状三/三元氢氧化物。另外，在pH 7.5下，Ni和Zn在二元体系中没有竞争性吸附作用。综上所述，这些结果表明pH值对反应产物具有至关重要的影响，并为理解潜在的迁移率，生物利用度，