Chen Wen L, Grabowski Robert C, Goel Saurav
School of Water, Energy and Environment, Cranfield University, Cranfield, Bedfordshire MK43 0AL, U.K.
London South Bank University, London SE1 0AA, U.K.
ACS Omega. 2022 Jan 17;7(4):3185-3191. doi: 10.1021/acsomega.1c04384. eCollection 2022 Feb 1.
The stepwise hydration of clay minerals has been observed repeatedly in studies, but the underlying mechanism remains unclear. Previous numerical studies confirmed the presence of one-water layer (1W) and two-water layer (2W) hydration states. However, the undisturbed transition between these hydration states has never been captured. Using molecular dynamics simulation, this study (i) simulated for the first time the free 1W-2W transition during clay hydration and (ii) identified the underlying mechanism to be the detachment of cations from the clay surface and the formation of a shell of water molecules around the cation. The swelling dynamics of clay was found to be affected by the clay charge, clay mineralogy, and counterions through complex cation-clay interactions, cation hydration capacity, and cation migration rate.
在研究中已多次观察到粘土矿物的逐步水化现象，但其潜在机制仍不清楚。先前的数值研究证实了单水层（1W）和双水层（2W）水化状态的存在。然而，这些水化状态之间未受干扰的转变从未被捕捉到。本研究通过分子动力学模拟，（i）首次模拟了粘土水化过程中自由的1W - 2W转变，（ii）确定其潜在机制是阳离子从粘土表面脱离以及在阳离子周围形成一层水分子。研究发现，粘土的膨胀动力学受粘土电荷、粘土矿物学以及抗衡离子的影响，其作用方式包括复杂的阳离子 - 粘土相互作用、阳离子水化能力和阳离子迁移速率。
