附聚作用驱动碳酸盐和碳酸氢盐在气-水界面上的反分馏
Agglomeration Drives the Reversed Fractionation of Aqueous Carbonate and Bicarbonate at the Air-water Interface
摘要：
在我们研究离子吸附到空气-水界面的过程中，我们先前报道了令人惊讶的结果，即双电荷碳酸根阴离子比单电荷碳酸氢根阴离子表现出更强的表面亲和力。与通常在界面区域中显示增强的浓度的单价弱水合阴离子相反，预期多价（和强水合）阴离子显示弱得多的表面倾向。在目前的工作中，我们使用共振增强深紫外二次谐波发生光谱测量的吉布斯自由能的吸附碳酸根（$CO_3^{2-}$）和碳酸氢根$(HCO_3^-)$阴离子的空气-水界面。对比经典静电理论的预测，并支持我们以前的研究结果，从X射线光电子能谱学，我们发现，碳酸根阴离子确实表现出更强的表面亲和力比碳酸氢根阴离子。分子动力学模拟表明，强离子配对的$CO_3^{2-}$与$Na^+$抗衡阳离子在界面区域，导致形成近中性的聚结物的$Na^+$和$CO_3^{2-}$团簇，是负责这种违反直觉的行为。这些发现不仅推进了我们对离子吸附化学的基本理解，而且还将影响重要的实际过程，如海洋酸化，海洋喷雾气溶胶化学和哺乳动物呼吸生理学。
英文摘要：
In the course of our investigations of the adsorption of ions to the air-water interface, we previously reported the surprising result that doubly-charged carbonate anions exhibit a stronger surface affinity than do singly-charged bicarbonate anions. In contrast to monovalent, weakly hydrated anions, which generally show enhanced concentrations in the interfacial region, multivalent (and strongly hydrated) anions are expected to show much weaker surface propensity. In the present work, we use resonantly enhanced deep-UV second harmonic generation spectroscopy to measure the Gibbs free energy of adsorption of both carbonate ($CO_3^{2-}$) and bicarbonate $(HCO_3^-)$ anions to the air-water interface. Contrasting the predictions of classical electrostatic theory, and in support of our previous findings from X-ray photoelectron spectroscopy, we find that carbonate anions do indeed exhibit much stronger surface affinity than do the bicarbonate anions. Molecular dynamics simulation reveals that strong ion pairing of $CO_3^{2-}$ with the $Na^+$ counter-cation in the interfacial region, resulting in formation of near-neutral agglomerates of $Na^+$ and $CO_3^{2-}$ clusters, is responsible for this counterintuitive behavior. These findings not only advance our fundamental understanding of ion adsorption chemistry, but will also impact important practical processes such as ocean acidification, sea-spray aerosol chemistry, and mammalian respiration physiology.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
