MXene-TiO2 mesoporous membranes on α-Al2O3 hollow fiber supports are prepared and regulated by adjusting the two-dimensional (2D) MXene content. The prepared MXene-TiO2 membranes are characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and x-ray diffraction. The results show that TiO2 nanoparticles (NPs) are uniformed deposited on 2D platforms and that the 2D structure of the original MXenes is still preserved in the film after calcination, thereby successfully inhibiting sol infiltration into the porous support. The obtained MXene-TiO2 layer with a controllable thickness exhibits ‘ideal’ pathways (longitudinal-lateral transport nanochannel) for dextran molecules between the TiO2 NPs and MXene nanosheets. Furthermore, the MXene-TiO2 membranes show higher rejection performance of dextran with increasing 2D MXene content. The optimal mesoporous MXene-TiO2 hollow fiber membranes exhibit a cut-off molecular weight (MWCO) of 14 854 Da and a high pure water flux of 102 l m−2 h−1 per bar, thereby showing good potential as high-performance interlayers for ceramic nanofiltration membranes.
A simple and scalable method was proposed for the preparation of the mesoporous membranes by assembling 2D MXene nanosheets and TiO2 nanoparticles (NPs) on a macroporous support. MXene nanosheets were introduced into TiO2 hydrosol, and then transformed the gel for fabrication of mesoporous TiO2@MXene membranes. Characterization results confirmed that an assembled structure of TiO2@MXene nanosheets was formed, benefiting from the nanosheets as 'floor tiles', thereby successfully inhibiting the sol infiltration into the porous support. As a result, the hydrosols could be directly coated on macroporous substrates including a disc support with an average pore size of ~100 nm and a four-channel hollow fiber with an average pore size of ~300 nm. It should be emphasized that the integrated disc or hollow fiber TiO2@MXene membranes were fabricated by only one single cycle of coating, aging and calcination. A range of advanced membrane characterization techniques were employed to study the ultrastructure of the fabricated membranes and the assumption of introducing nanosheets to prevent membrane defect and gel infiltration was validated.Filtration experiments revealed the resulted membranes, in particular the hollow fiber TiO2@MXene membranes, had a narrow pore size distribution, desirable rejection chacteristics and high permeate flux. The 2D nanosheet assisted TiO2 NPs assembly proposed in this work promises a simple, feasible and scalable approach for fabrication of high-performance mesoporous TiO2 membranes.
A thinner Y-TZP specimen was likely to present surface defects and microcracks after aging. In addition, the flexural strengths decreased with a decrease in the thickness, a notable fact for further studies.
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