Carboxymethylcellulose (CMC)/glutaraldehyde (GA)-modified Ti3C2Tx membrane and its efficient ion sieving performance

2D nanosheet membranes show promise for ion sieving. However, nanosheet swelling still adversely affects the ion sieving performance. In this study, Ti3C2Tx was mixed with carboxymethylcellulose sodium (CMC) and stirred in an ice bath; then, glutaraldehyde (GA) was added to cross-link the CMC distributed between Ti3C2Tx interlayers to obtain a CMC/GA-modified Ti3C2Tx membrane (C@TM). The strong chemical bonding between the Ti3C2Tx andd CMC prevented swelling of the Ti3C2Tx nanosheets in aqueous solutions. A stable effective inter -layer spacing (4.8 +/- 0.1 angstrom) was obtained, and the mechanical strength of the membrane was improved. Due to size sieving and image force repulsions, C@TM exhibited efficient divalent ion retention performance. The C@TM selectivity for monovalent/divalent ions was approximately 30; this value was 14 times higher than that of the original Ti3C2Tx membrane (OTM). In addition, based on aldol condensation reaction, GA blocked the exposed oxygen-containing groups in the CMC to form a water-insoluble macromolecular network, which improved the water stability of the membrane. C@TM exhibited excellent membrane performance during long-term (72 h) operation. The effects of applied voltages on the separation performance were tested. The results showed that Mg2+ transport was significantly inhibited at-0.6 V, and the Li+/Mg2+ selectivity was increased.

Automated summary

In this study, a modified Ti3C2Tx membrane (C@TM) was prepared by mixing Ti3C2Tx with CMC and cross-linking the CMC, which effectively reduced the swelling of the membrane and improved its mechanical strength. The C@TM exhibited efficient ion sieving performance and excellent long-term stability during operation.