Ion-Responsive Channels of Zwitterion-Carbon Nanotube Membrane for Rapid Water Permeation and Ultrahigh Mono-/Multivalent Ion Selectivity

Abstract

The rational combination of polymer matrix and nanostructured building blocks leads to the formation of composite membranes with unexpected capability of selectivity of monovalent electrolytes and water, which affords the feasibility to effeciently remove harmful ions and neutral molecules from the environment of concentrated salines. However, the multivalent ion rejection in salined water of routine nanocomposite membranes was less than 98% when ion strength is high, resulting in a poor ion selectivity far below the acceptable value. In this contribution, the ion-responsive membrane with zwitterion-carbon nanotube (ZCNT) entrances at the surface and nanochannels inside membrane has been proposed to obtain ultrahigh multivalent ion rejection. The mean effective pore diameter of ZCNT membrane was dedicated tuned from 1.24 to 0.54 nm with the rise in Na2SO4 concentration from 0 to 70 mol m(-3) as contrary to the conventional rejection drop in carbon nanotube (CNT) membrane. The ultrahigh selective permeabilities of monovalent anions against divalent anions of 93 and against glucose of 5.5 were obtained on ZCNT membrane, while such selectivities were only 20 and 1.6 for the pristine CNT membrane, respectively. The ZCNT membranes have potential applications in treatment of salined water with general NaCl concentration from 100 to 600 mol m(-3), which are widely applicable in desalination, food, and biological separation processes.

Ultrathin Alginate Coatings as Selective Layers for Nanofiltration Membranes with High Performance

“…Furthermore, TFC NFMs with high mono‐/divalent ion selectivity have many potential applications in water treatment, the food industry, and biological separation processes . It has been proven that NFMs with highly charged surfaces tend to have good mono‐/divalent ion selectivity .…”

“…Furthermore, TFC NFMs with high mono-/divalent ion selectivity have many potential applications in water treatment, the food industry,a nd biologicals eparation processes. [46,47] It has been proven that NFMs with highly charged surfaces tend to have good mono-/divalent ion selectivity. [48,49] Thus it was quite reasonable for us to consider using the alginate TFC NFMs for mono-/divalent ion separation.…”

Preparation of organic–inorganic hybrid membranes with superior antifouling property by incorporating polymer-modified multiwall carbon nanotubes

“…In particular, CNTs have a hollow tubular structure, which can favorably function as a transport channel for water molecules. 18 Thus, the introduction of CNTs into a membrane matrix would signicantly enhance the membrane permeability. Nevertheless, CNTs tend to aggregate into bundles due to their strong van der Waals interactions, and this makes their uniform dispersal difficult in various solvents and polymer membranes.…”

The averaged potential gradient approach to model the rejection of electrolyte solutions using nanofiltration: Model development and assessment for highly concentrated feed solutions

“…At the same time, the extensive studies carried out on the theoretical influence of image charges clearly stress their theoretical significance [22,26,27,36] and some experimental results also point towards the importance of taking the low dielectric constant of the membrane matrix into account [37].…”