Department of Earth and Environmental Engineering, Columbia University, New York, New York 10027, USA.
School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona 85287-9309, USA.
J Chem Phys. 2018 Oct 28;149(16):164708. doi: 10.1063/1.5027105.
Ion hydration is a fundamental process in many natural phenomena. This paper presents a quantitative analysis, based on atomistic modeling, of the behavior of ions and the impact of hydration in a novel CO sorbent. We explore moisture-driven CO sorbents focusing on diffusion of ions and the structure of ion hydration complexes forming inside water-laden resin structures. We show that the stability of the carbonate ion is reduced as the water content of the resin is lowered. As the hydration cloud of the carbonate ion shrinks, it becomes energetically favorable to split a remaining water molecule and form a bicarbonate ion plus a hydroxide ion. These two ions bind less water than a single, doubly charged carbonate ion. As a result, under relatively dry conditions, more OH ions are available to capture CO than in the presence of high humidity. Local concentrations of dissolved inorganic carbon and water determine chemical equilibria. Reaction kinetics is then driven to a large extent by diffusion rates that allow water and anions to move through the resin structure. Understanding the basic mechanics of chemical equilibria and transport may help us to rationally design next-generation efficient moisture-driven CO sorbents.
离子水化是许多自然现象中的基本过程。本文基于原子建模，对离子的行为以及在新型 CO 吸附剂中水化的影响进行了定量分析。我们专注于研究水分驱动的 CO 吸附剂，探讨了离子的扩散以及在含水树脂结构中形成的离子水化络合物的结构。结果表明，随着树脂含水量的降低，碳酸根离子的稳定性降低。随着碳酸根离子水化云的收缩，分裂剩余水分子并形成碳酸氢根离子和氢氧根离子变得更加有利。这两种离子结合的水分子比单个、双电荷的碳酸根离子少。因此，在相对干燥的条件下，与高湿度环境相比，可用于捕获 CO 的 OH 离子更多。溶解的无机碳和水的局部浓度决定了化学平衡。反应动力学在很大程度上受到扩散速率的驱动，这些扩散速率允许水和阴离子通过树脂结构移动。了解化学平衡和传输的基本力学原理可能有助于我们合理设计下一代高效水分驱动的 CO 吸附剂。
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