Ion-Selective Separation Using MXene-Based Membranes: A Review

Abstract

Global lack of clean water makes it essential that new technologies are developed for separation of pollutants from raw water. Membrane separation has arisen as a promising solution among other conventional liquid-separation processes, such as evaporation, distillation, and crystallization. Synthetic polymer membranes have been emphasized as an important component in liquid separation processes due to their outstanding water/salt selectivity and ionic conductivity. However, their inherent trade-off between selectivity and permeability has remained a challenge for polymeric membranes. Recently, two-dimensional nanomaterials have been actively sought after as an alternative to polymeric membranes. MXene, a new type of nanomaterial, has been attracting considerable attention as a building block for nanostructured separation membranes. Due to several appealing features, such as their surface functional groups with negative charge, they have been used in size-, charge-, and adsorption-selective separation for different ions or molecules. This article reviews recent progress in MXene-based membranes, with a particular emphasis on ion-selective separation and their applications for water purification including salt rejection, reverse electrodialysis, or heavy metal adsorption. Lastly, the challenges and future directions of MXene-based ion-selective membranes are discussed.

A Laser‐Induced Mo2CTx MXene Hybrid Anode for High‐Performance Li‐Ion Batteries

“…[2,10,11] They are synthesized by selectively exfoliating the A layers (primarily members of groups 13 and 14) from their parent layered ternary carbide phases (MAX) using fluoride-containing etchants. [11][12][13] Since their discovery in 2011 by Naguib et al, [14] MXenes have offered exceptional performance in various application fields, [15][16][17][18][19] especially in energy storage, [20] owing to their unique combination of impressive electrochemical and physicochemical properties associated with their versatile surface chemistry and weak interlayer (van der Waals) interactions. [10][11][12][13][14][15][16][17][18][19][20][21][22][23] More specifically, their metal-like conductivity, superior hydrophilicity, largely tunable interlayer spacing, and ability to host different cations between their layers have enabled excellent rate capability, cycling stability, higher tap density, and volumetric capacity compared to graphene, reduced graphene oxides, and TMDs.…”

“…[11][12][13] Since their discovery in 2011 by Naguib et al, [14] MXenes have offered exceptional performance in various application fields, [15][16][17][18][19] especially in energy storage, [20] owing to their unique combination of impressive electrochemical and physicochemical properties associated with their versatile surface chemistry and weak interlayer (van der Waals) interactions. [10][11][12][13][14][15][16][17][18][19][20][21][22][23] More specifically, their metal-like conductivity, superior hydrophilicity, largely tunable interlayer spacing, and ability to host different cations between their layers have enabled excellent rate capability, cycling stability, higher tap density, and volumetric capacity compared to graphene, reduced graphene oxides, and TMDs. [24][25][26] Although there are 30+ different synthesized MXenes, [27] the research on MXene-based energy storage has mainly focused on Ti-based MXenes, particularly Ti 3 C 2 T x , the most mature member of the MXene family.…”

Harvesting Blue Energy Based on Salinity and Temperature Gradient: Challenges, Solutions, and Opportunities

“…Recently, Hong et al created perforated nanopores over Ti 3 C 2 T x MXene nanosheets by facile H 2 SO 4 oxidation. 234 Using a 100-fold KCl salt concentration gradient across the modified membrane, a peak power density of 17.5 W/m 2 was attained, 38% higher than that of the pristine MXene membrane.…”

Electric Field-Assisted Ion Separation Using Ceramic-Based Thermally Cross-Linked MXene Membranes

“…Efficient ion separationa key process in sustainable water purification and resource recovery of valuable seawater cationsrepresents a formidable challenge. − Hence, developing multifunctional, scalable, and highly efficient state-of-the-art purification technologies to augment dwindling freshwater supplies and recover value-added products is imperative. − Membrane-based separation has demonstrated immense potential for water purification and resource recovery, primarily because of the distinct merits, such as high separation efficiency, environmental friendliness, and continuous operation. − Recently, emerging two-dimensional (2D) membranes, such as graphene oxide (GO), , transition metal carbide/nitrides (MXenes), − and metal–organic frameworks (MOFs), have attracted considerable interest due to their subnanometer-level narrow nanochannels that are similar to biomimetic smart nanochannels, demonstrating exceptional selective sieving ability for precise ion separation.…”