Structure Dependent Water Transport in Membranes Based on Two-Dimensional Materials

Abstract

The upsurge in population and industrialization has instigated the demand in improvement in the existing water purification systems. Numerous organic, and later inorganic materials, have showcased huge potential in different membrane separation processes. Recently, a novel range of two-dimensional (2D) materials possessing atomic thickness, high robustness, excellent mechanical stability, and even great fouling resistance have shown their appealing potential as membrane materials in this respect. The high aspect ratios of 2D materials enable the feasible control of membrane assembled structures. The membrane structure of 2D materials plays a crucial role in separation performance. Regarding the molecular transport pathway, the assembled structure is categorized into laminates and in-plane pores here. From this aspect, this review discusses the most recently progress of 2D materials membranes, including graphene-based materials, MXenes, transition metal dichalcogenides, metal organic frameworks, covalent organic frameworks, and boron nitride, in the field of water purification. According to their membrane assembled structures, the design strategies with separation mechanism and separation performance have been reviewed. Lastly, challenges and futuristic upgrades to enhance their membrane operation are discussed accordingly. This review provides a new perspective of 2D material assemblies on membrane design for advancing separation performance in water purification.

Functional groups in graphene oxide

“…Graphene oxide (GO) has been extensively studied in the last decades for various applications such as filtration, energy storage, and sensing, owing to its remarkable physico-chemical properties. [1][2][3][4][5][6][7][8][9] GO consists of a one-atom-thick planar sheet decorated with hydrophobic sp 2 carbon and hydrophilic functionalities, including hydroxyl and epoxide groups on the basal plane and carboxyl groups on the edges. 10,11 As GO is a heterogeneous material, its properties and corresponding applications are determined by its structure and composition.…”

A novel covalent organic framework for efficient photocatalytic reduction of Cr(vi) and synergistic removal of organic pollutants under visible light irradiation

“…Contaminated wastewater must be rigorously treated and purified before it can be discharged, which improves the quality of the water environment and provides significant economic advantages. Standard treatment methods, for instance, membrane separation, 8 chemical precipitation, 9 adsorption, 10 biodegradation, 11 and photocatalytic techniques, 12 have been widely used to remove contaminated wastewater containing organic dyes and Cr( vi ). In particular, photocatalytic technology is an advanced oxidation technology that uses green and renewable light to photodegrade harmful substances, converting solar energy into chemical energy.…”

High‐Flux and High‐Selectivity Graphene Oxide Membrane Prepared by a Two‐step Reduction Method for Metal Ion Separation

“…[7][8][9] Graphene oxide (GO) membrane and its derivative reduced graphene oxide (rGO) membrane have great research space in the field of membrane separation due to their excellent membrane-forming properties, simple physical models, and rich modifiabilities. [10][11][12][13][14] However, due to the strong hydrophilicity of GO membrane, it swells after absorbing water and expands the interlayer distance, [15] which made it possible to separate small-size ions, such as seawater desalination, [16,17] metal ion selective separation, [18,19] purification of dye wastewater [20] and some other restricted fields. [16,17] The hydration diameters of monovalent metal ions are 6.62 Å-7.64 Å, while those for multivalent metal ions are 8.02 Å-9.50 Å.…”

“…Also membranes had very excellent performance in the field of new energy, such as the separator for flow batteries [3–6] and the separation of lithium and magnesium [7–9] . Graphene oxide (GO) membrane and its derivative reduced graphene oxide (rGO) membrane have great research space in the field of membrane separation due to their excellent membrane‐forming properties, simple physical models, and rich modifiabilities [10–14] . However, due to the strong hydrophilicity of GO membrane, it swells after absorbing water and expands the interlayer distance, [15] which made it possible to separate small‐size ions, such as seawater desalination, [16,17] metal ion selective separation, [18,19] purification of dye wastewater [20] and some other restricted fields [16,17] …”