Role of hydration energy and co-ions association on monovalent and divalent cations adsorption at mica-aqueous interface

Abstract

Adsorption of ions at the solid - aqueous interface is the primary mechanism in fast biological processes to very slow geological transformations. Despite, little is known about role of ion charge, hydration energy and hydration structure on competitive adsorption of ions, their structure and coverage at the interface. In this report, we investigate the structure and adsorption behavior of monovalent (Rb+ and Na+) and divalent (Sr2+ and Mg2+) cations ranging from 0–4.5 M of bulk concentrations on the muscovite mica surface. Divalent ions have stronger adsorption strength compared to monovalent ions due higher charge. However, we observed counter-intuitive behavior of lesser adsorption of divalent cations compared to monovalent cations. Our detailed analysis reveals that hydration structure of divalent cations hinders their adsorption. Both, Na+ and Rb+ ions exhibits similar adsorption behavior, however, the adsorption mechanism of Na+ ions is different from Rb+ ions in terms of redistribution of the water molecules in their hydration shell. In addition, we observed surface mediated RbCl salting out behavior, which is absent in Na+ and divalent ions. We observed direct correlation in hydration energy of cations and their adsorption behavior. The obtained understanding will have tremendous impact in super-capacitors, nanotribology, colloidal chemistry and water purifications.

Self-assembly and adsorption of cetyltrimethylammonium bromide and didodecyldimethylammonium bromide surfactants at the mica–water interface

“…42,44,59 The layering extends to about 10 Å into the liquid, which is in excellent agreement with that seen in earlier work. 42,44,59 Fig. 3(c) shows that the water adjacent to the surface with potassium is less well ordered, but the weak layering extends a similar distance into the liquid.…”

“…3(d), the peak labelled P 1 has been reported in other work as the 'adsorption layer', while the peak labelled P 2 is referred to as the 'hydration layer'. 42,44,59 The distance between the two peaks is 2.8 Å, which is larger than the value of 1.2 Å estimated in previous work using high-resolution specular X-ray reflectivity, and Monte Carlo and MD simulations. 42,44,59 The layering extends to about 10 Å into the liquid, which is in excellent agreement with that seen in earlier work.…”

“…42,44,59 The distance between the two peaks is 2.8 Å, which is larger than the value of 1.2 Å estimated in previous work using high-resolution specular X-ray reflectivity, and Monte Carlo and MD simulations. 42,44,59 The layering extends to about 10 Å into the liquid, which is in excellent agreement with that seen in earlier work. 42,44,59 Fig.…”

An extended generalized effective stress for active clays

“…The properties of water are expected to remain constant, and typical of a liquid water, from the first nanometer onwards (e.g. [11,12,13]).…”

Ion Distribution and Hydration Structure at Solid–Liquid Interface between NaCl Crystal and Its Solution

“…It was found that both ions and water molecules exhibit a layerlike structure in the direction perpendicular to the interface. 15,17−31 Besides, the water molecules 19−21,24−26,28,30,32 and ions 14,19,20,24,25,28,30,32,33 at the interface are laterally ordered with respect to the crystal structure. The dipole moment of water molecules at the SLI also tends to be ordered.…”