The Preparation of High-Performance and Stable MXene Nanofiltration Membranes with MXene Embedded in the Organic Phase

Abstract

Nanomaterials embedded in nanofiltration membranes have become a promising modification technology to improve separation performance. As a novel representation of two-dimensional (2D) nanomaterials, MXene has nice features with a strong negative charge and excellent hydrophilicity. Our previous research showed that MXene nanosheets were added in the aqueous phase, which enhanced the permeselectivity of the membrane and achieved persistent desalination performance. Embedding the nanomaterials into the polyamide layer through the organic phase can locate the nanomaterials on the upper surface of the polyamide layer, and also prevent the water layer around the hydrophilic nanomaterials from hindering the interfacial polymerization reaction. We supposed that if MXene nanosheets were added in the organic phase, MXene nanosheets would have more negative contact sites on the membrane surface and the crosslinking degree would increase. In this study, MXene were dispersed in the organic phase with the help of ultrasound, then MXene nanocomposite nanofiltration membranes were achieved. The prepared MXene membranes obtained enhanced negative charge and lower effective pore size. In the 28-day persistent desalination test, the Na2SO4 rejection of MXene membrane could reach 98.6%, which showed higher rejection compared with MXene embedded in aqueous phase. The results of a long-time water immersion test showed that MXene membrane could still maintain a high salt rejection after being soaked in water for up to 105 days, which indicated MXene on the membrane surface was stable. Besides MXene membrane showed high rejection for high-concentration brine and good mono/divalent salt separation performance in mono/divalent mixed salt solutions. As a part of the study of MXene in nanofiltration membranes, we hoped this research could provide a theoretical guidance for future research in screening different addition methods and different properties.

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

“…Research to test the long-term structural and performance-based stability of membranes is emerging. Therefore, either long-term measurements ,, or long time water immersion tests ,, are carried out in order to provide knowledge about the stability. The longest desalination test was carried out about 58 days for Ti 3 C 2 T x -based TFN membranes without the decrease in salt rejection .…”

MXene-Based Nanomaterials for Multifunctional Applications

“…Therefore, Ti 3 C 2 T x MXene shows potential advantages in improving the desalination performance of NF membranes. This recent finding could provide theoretical guidance for future research in this field [ 99 ].…”

Effect of MXene Nanosheet Dispersed Phases on the Fabrication of Polyamide Nanofiltration Membranes

“…The zeta potential of the MA and MO membranes was lower than the TFC membrane because of negative MXene nanosheets modification, which corresponded to previous reports. 32,35 Because of the enhanced negative charge, the ions' repulsion was enhanced by the Donnan effect. This can explain why the salt rejection of the MA and MO membranes was higher than the TFC membranes.…”

“…Wang and his colleagues employed MXene nanosheets to prepare RO membranes with antifouling and chlorine resistance . Current research reports indicate that high-performance TFN membranes can be prepared by dispersing MXene nanosheets into the aqueous − or organic phases . However, the action mechanism and performance difference of MXene in different dispersed phases are also not explained.…”

“…33 Current research reports indicate that high-performance TFN membranes can be prepared by dispersing MXene nanosheets into the aqueous 32−34 or organic phases. 35 However, the action mechanism and performance difference of MXene in different dispersed phases are also not explained. There is currently also little research on the differences and mechanisms of 2D nanosheets dispersed into aqueous and organic phases.…”