Abstract
Novel two-dimensional (2D) membranes have been utilized in water purification or seawater desalination due to their highly designable structure. However, they usually suffer from swelling problems when immersed in solution, which limits their further applications. In this study, 2D cross-linked MXene/GO composite membranes supported on porous polyamide substrates are proposed to improve the antiswelling property and enhance the ion-sieving performance. Transition-metal carbide (MXene) nanosheets were intercalated into GO nanosheets, where the carboxyl groups of GO combined the neighboring hydroxyl terminal groups of MXene with the formation of -COO- bonds between GO and MXene nanosheets via the cross-linking reaction (−OH + −COOH = −COO− + H2O) after heat treatment. The permeation rates of the metal ions (Li+, Na+, K+, Al3+) through the cross-linked MXene/GO composite membrane were 7–40 times lower than those through the pristine MXene/GO membrane. In addition, the cross-linked MXene/GO composite membrane showed excellent Na+ rejection performance (99.3%), which was significantly higher than that through pristine MXene/GO composite membranes (80.8%), showing improved ion exclusion performance. Such a strategy represents a new avenue to develop 2D material-derived high-performance membranes for water purification.
Highlights
Membrane-based separation technology has played an increasingly important role in water purification because of its cost-effectiveness, energy efficiency, and easy operation [1,2,3,4,5]
The preparation of the MXene nanosheet solution, the raw materials used in this process and the calculation of its concentration are described in our previous work [44]
The AFM images (Figure 3a–d) and the SEM images (Figure 3e–h) of the MXene and GO nanosheets indicate that the MXene nanosheets exhibited an average thickness of ~1.3 nm with a lateral size in the range of several hundreds of nanometers to a few microns, was performed using Rigaku Smart Lab X-Ray Diffractometer (Japan) with filtered Cu-Kα radiation (40 kV and 40 mA, λ = 0.154 nm)
Summary
Membrane-based separation technology has played an increasingly important role in water purification because of its cost-effectiveness, energy efficiency, and easy operation [1,2,3,4,5]. 2D membranes have been widely studied in molecular sieving, including gas, metal ions, solvent, dye, etc. As one kind of crucial 2D nanomaterial, graphene oxide (GO), has great potential for separation application processes [14]. Due to their superior ion selectivity, good mechanical strength, versatile chemical modification, and antifouling potential, GO membranes are promising for water purification [6,15,16,17,18,19,20,21].
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