Lamellar MXene Nanofiltration Membranes for Electrostatic Modulation of Molecular Permeation: Implications for Fine Separation

Abstract

Nanofiltration membrane-based molecular separation has become an indispensable technology for fine sieving processes. However, the difficulty in regulating the separation performance restricts the applicability of these nanofiltration membranes in different separation systems. Herein, we will show that the separation performance of Ti 3 C 2 T x −MXene lamellar nanofiltration membranes on certain dye molecules can be modulated by employing external electrostatic fields. Specifically, for cationic dyes, the negative voltage applied to Ti 3 C 2 T x lamellar nanofiltration membranes can improve their sieving abilities on dyes but reduce their water flux at the same time. On the contrary, a positive electric field will cause a decline in the retention capacities but improve the water flux of the membranes. Interestingly, when using anionic dye molecules as solute models, the filtration performance of the Ti 3 C 2 T x membranes exhibits completely opposite variations to that of filtering cationic dyes, whether the applied electric field is negative or positive. The regulation mechanisms for the filtration performance of Ti 3 C 2 T x membranes have been discussed, which are probably ascribed to the changes in the electrostatic interactions between dyes and Ti 3 C 2 T x induced by the external electric field. Our findings indicate that the filtration performance of MXene lamellar membranes on both cationic and anionic dyes can be modulated by applying an external electric field, opening up enormous opportunities to use such electrified nanofiltration membranes in the field of membrane-based molecular separations.

Can MXene be the Effective Nanomaterial Family for the Membrane and Adsorption Technologies to Reach a Sustainable Green World?

“…It was also suggested that on top of the size-sieving ability of MXene membranes, their voltage-gated sieving ability could be used for dye separation benefiting from the electrostatic interactions between dyes and MXene, which are regulated by changing the applied external voltage. 235,236 Therefore, it reveals that the separation performance of MXene membranes can be enhanced via mean contribution of different driving forces.…”

MXenes and MXene-Based Materials for Removal and Detection of Water Contaminants: A Review

“…The high rejection rates of dyes were also demonstrated as 93.1% for Congo red and 94.8% for aniline blue under the application of −3 V, suggesting the potential of these membranes for regulated water transport as well as water treatment. The electrostatic interactions between dye molecules and Ti 3 C 2 T x membranes were also shown to modulate the separation performance for nanofiltration membranes . The application of negative voltage to the membranes provided better sieving of cationic dyes but reduced the water permeation, whereas the positive voltage reduced the retention and improved the water flux.…”

“…The electrostatic interactions between dye molecules and Ti 3 C 2 T x membranes were also shown to modulate the separation performance for nanofiltration membranes. 43 The application of negative voltage to the membranes provided better sieving of cationic dyes but reduced the water permeation, whereas the positive voltage reduced the retention and improved the water flux. However, an opposite behavior was observed in the case of anionic dyes, irrespective of the electric field being positive or negative.…”

Membranes prepared from graphene-based nanomaterials for water purification: a mini-review

“…NF for GBnM membranes is typically governed by the following separation mechanisms: 52,53 (1) physical adsorption or chemical interaction (i.e., cation-π interaction) between solute molecules and the surfaces of mass transport channels, (2) molecular sieving controlled by size exclusion, and (3) the Gibbs-Donnan effect (i.e., electrostatic repulsion) between charged solutes and charged groups anchored to the membrane surface. These mechanisms are interconnected, and the last two modes are more important in NF processes.…”

“…NF for GBnM membranes is typically governed by the following separation mechanisms: 52,53 (1) physical adsorption or chemical interaction ( i.e. , cation–π interaction) between solute molecules and the surfaces of mass transport channels, (2) molecular sieving controlled by size exclusion, and (3) the Gibbs–Donnan effect ( i.e.…”