(399q) Two-Dimensional Mxene Membrane for Water Purification

Authors: 
Wang, H., South China University of Technology
Wei, Y., South China University of Technology
Two-dimensional MXENE MEMBRANE for WATER PURIFICATION

Li Ding, Yanying Wei, Haihui Wang*

South China University of Technology, School of Chemistry and Chemical Engineering, No. 381 Wushan Road, Guangzhou 510640, Guangdong, China

Corresponding author: hhwang@scut.edu.cn Introduction

Two-dimensional (2D) materials are considered to be promising candidates for advanced membrane separation process. Several 2D materials, such as graphene and graphene oxide (GO),[1] exfoliated nanosheets of metal-organic frameworks (MOFs)[2] and zeolite nanosheets,[3] and the transition metal dichalcogenides (TMDs),[4] have attracted increasing attention in preparing for future functional separation membranes due to their outstanding mechanical properties, excellent thermal stability and superior flexibility. Nowadays, a novel kind of 2D layered material named MXenes - a family of early transition metal carbides, has received increasing attention. MXene is normally produced by selectively etching the A layer from MAX phases. Owing to its flexibility, superior structural stability, high electrical conductivity and hydrophilic surfaces, MXene has been widely used in super capacitors,[5] Lithium-ion batteries,[6] oxygen-evolution reaction,[7] and heavy metal adsorption.[8] However, there so far no report on the inorganic MXene-based membranes till now, except the paper by Gogotsi et al. for ion sieving.[9] Herein, we propose a kind of 2D lamellar membranes with Ti3C2TX MXene nanosheets, and its application in water purification.

Keywords: Two-dimensional • MXene • Ti3C2TX • membrane • separation • water purification Experimental

The preparation of the MXene membrane for water purification is as follows. First, Ti3AlC2 particles were first etched by HF solution to generate Ti3C2TX powder. By extracting Al as AlF3, the interaction between the layers is weakened. The MXene nanosheets can be obtained by sonication-assisted exfoliation. Second, the positively charged Fe(OH)3 colloidal solution was chosen to intercalate the negatively charged MXene nanosheets to create expanded nanochannels. Subsequently, after a simple vacuum filtration process and hydrochloric acid solution (HCl) treatment to remove the Fe(OH)3 nanoparticles, the ultimate MXene membrane can be obtained. Results and discussion

The MXene membrane supported on anodic aluminum oxide (AAO) substrate shows excellent water permeance (more than 1000 L m-2 h-1 bar-1) and favorable rejection rate (over 90 %) for molecules with sizes larger than 2.5 nm. The water permeance through the MXene membrane is much higher than that of the most membranes with similar rejections. Additionally, the long-time operation reveals the outstanding stability of the MXene membrane for water purification.

Conclusions

In summary, a new kind of a 2D lamellar membrane based on stacks of Mxene nanosheets are prepared successfully by filtration deposition on AAO substrates. During the on-filtration, colloidal Fe(OH)3 has been used as distance holder followed by HCl dissolution. The MXene membrane exhibits an excellent water permeance (more than 1000 L m-2 h-1 bar-1) and a high rejection rate (90 %) for molecules with sizes larger than 2.5 nm when applied in water purification. Mxenes, as a new kind of 2D materials, opens a door for the development of highly efficient membranes for water treatment, selective gas separation and other practical separation applications.

Acknowledgment

We gratefully acknowledge the funding from by the Sino-German center for Science Promotion (GZ 911), the Natural Science Foundation of China for Distinguished Young Scholars of China (no. 21225625), Natural Science Foundation of China (21536005, 51621001) and the Natural Science Foundation of the Guangdong Province (2014A030312007).

References

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