Surface processes of Np on selected mineral oxides. Vibrational spectroscopic investigations

Np(V)在矿物氧化物上的不同界面络合物的结构将在分子水平上进行鉴定。界面络合物将在特定和环境相关的条件下通过改变选择性参数，如溶剂的pH或离子强度，以及通过促进不同的表面络合途径来研究。到目前为止，还没有确定中间齐聚物、胶体或沉淀分子复合体的结构，尽管对它们的存在有科学上的共识。作为本项目的主要创新，将对可能的吸附过程，即单体和低聚表面络合物的形成，以及表面沉淀物或表面胶体的形成进行光谱研究。这反过来将允许概括化学上相似但实验上难以访问的光化体系的反应模式，例如，PA或Pu。此外，这些结果将为已建立的准热力学吸附模型提供充分的方法来处理竞争过程，如地表降水。这些过程将主要在水溶液中用原位ATR红外光谱进行鉴定和表征。由于不同官能团的振动模式的特征频率通常在红外光谱中被很好地分离，这一技术将提供界面过程的全面的分子信息。还将应用互补的光谱技术，例如XAS和TRLFS，以及微观方法，例如AFM和CLSM。

The structures of different interface complexes of neptunium (Np(V)) at mineral oxides are to be identified on a molecular level. The interface complexes will be studied under specific and environmentally relevant conditions by variation of selective parameters, such as pH or ionic strength of the solvent, and by the promotion of different surface complexation pathways. The structures of intermediate oligomeric, colloidal or precipitated molecule complexes were not determined so far, although there is scientific agreement about their occurrence. As major innovation of this project, the possible sorption processes, namely the development of monomeric and oligomeric surface complexes, and the formation of surface precipitates or surface colloids will be spectroscopically investigated. This in turn will allow a generalization of reaction patterns of chemically similar but experimentally difficult to access actinyl systems, e.g., Pa or Pu. In addition, the results will supply well-established quasithermodynamic sorption models with adequate approaches for competing processes such as surface precipitation. The processes will be mainly identified and characterized in aqueous solution by in situ ATR FT-IR spectroscopy. Because the characteristic frequencies of the vibrational modes of distinct functional groups, i.e. the neptunyl ion and the ubiquitous inorganic ligand such as the carbonate anion, are generally well separated in the infrared spectra, this technique will provide comprehensive molecular information of the interface processes. Complementary spectroscopic techniques, e.g. XAS and TRLFS, and microscopic methods, e.g. AFM and CLSM will also be applied.