Structure and Dynamics of Water Confined in Imogolite Nanotubes

Abstract

We have studied the properties of water adsorbed inside nanotubes of hydrophilic imogolite, an aluminum silicate clay mineral, by means of molecular simulations. We used a classical force field to describe the water and the flexible imogolite nanotube, and validated it against data obtained from first-principles molecular dynamics. With it, we observe a strong structuration of the water confined in the nanotube, with specific adsorption sites and a distribution of hydrogen bond patterns. The combination of number of adsorption sites, their geometry and the preferential tetrahedral hydrogen bonding pattern of water leads to frustration and disorder. We further characterize the dynamics of the water, as well as the hydrogen bonds formed between water molecules and the nanotube, which are found to be more than one order of magnitude longer than water-water hydrogen bonds.

Heavy Metals Nanofiltration Using Nanotube and Electric Field by Molecular Dynamics

“…Among the sensors used to detect HM [35,36], some have high sensitivity to identify the kind and level of contamination, based on a threedimensional hybrid electrode system in CNT [64]. After HM or its compounds are detected, separation methods will be chosen, such as the use of chemical precipitation [65], reverse osmosis [31], filtration [45], adsorption on activated carbon [66], the use of adsorbents such as aluminosilicates [67,68], or processes of oxy-reduction [69].…”

“…NF membranes used to recycle wastewater, require high flow and energy rates during the NF process [66]. Reverse osmosis is the ideal separation method for ion removal [67], but it does not remove monovalent ions. NF can distinguish molecules based on their size or valence [72] and is often used to remove bi-or trivalent ions from water because they represent part of "water solids."…”

Structure, Dynamics and Thermodynamics of Intruded Electrolytes in ZIF-8

“…This slowdown of water dynamics under confinement is well-known, 38 and has been observed in many classes of nanoporous materials. 26,[40][41][42] It is attributed to the stronger organization of water as well as water molecules finding fewer partners for hydrogen bond exchange. The same arguments also apply to the increase in LiCl concentration, both in the bulk and confined liquid.…”

Water Induced Structural Transformations in Flexible Two-Dimensional Layered Conductive Metal–Organic Frameworks

“…Dynamics and adsorption of confined water have been widely studied in carbon nanotubes, 39,40 zeolitic imidazolate frameworks (ZIFs), 41,42 MOFs, 43−49 and imogolite nanotubes. 50 When it comes to 2D MOFs, little experimental data, if not no experimental data, is available on thermodynamics and dynamics of confined water in 1D channels. With the developed AIFFs, we characterize mobility of water with respect to (i) diffusion in 1D channels, (ii) adsorption by forming either hydrogen bonds with organic linkers or coordinative bonds with open-metal sites, and (iii) penetration within the interlayer spaces of these 2D π-stacked layered materials.…”