Ober Patrick, Hunger Johannes, Kolbinger Sophia H, Backus Ellen H G, Bonn Mischa
Department of Molecular Spectroscopy, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
University of Vienna, Faculty of Chemistry, Institute of Physical Chemistry, Waehringer Strasse 42, 1090, Vienna, Austria.
Angew Chem Int Ed Engl. 2022 Nov 14;61(46):e202207017. doi: 10.1002/anie.202207017. Epub 2022 Oct 13.
The dissolution of minerals in contact with water plays a crucial role in geochemistry. However, obtaining molecular insight into interfacial chemistry is challenging. Dissolution typically involves the release of ions from the surface, giving rise to a charged mineral surface. This charge affects the interfacial water arrangement, which can be investigated by surface-specific vibrational Sum Frequency Generation (v-SFG) spectroscopy. For the fluorite-water interface, recent spectroscopic studies concluded that fluoride adsorption/desorption determines the surface charge, which contrasts zeta potential measurements assigning this role to the calcium ion. By combining v-SFG spectroscopy and flow experiments with systematically suppressed dissolution, we uncover the interplay of dominant fluoride and weak calcium adsorption/desorption, resolving the controversy in the literature. We infer the calcium contribution to be orders of magnitude smaller, emphasizing the sensitivity of our approach.
与水接触的矿物质溶解在地球化学中起着至关重要的作用。然而，深入了解界面化学的分子机制具有挑战性。溶解通常涉及离子从表面释放，从而产生带电荷的矿物表面。这种电荷会影响界面水的排列，可通过表面特异性振动和频产生（v-SFG）光谱进行研究。对于萤石-水界面，最近的光谱研究得出结论，氟化物的吸附/解吸决定了表面电荷，这与将此作用归因于钙离子的zeta电位测量结果形成对比。通过将v-SFG光谱与流动实验相结合，并系统地抑制溶解，我们揭示了主要的氟化物与微弱的钙吸附/解吸之间的相互作用，解决了文献中的争议。我们推断钙的贡献要小几个数量级，强调了我们方法的敏感性。
