Highly permeable and dye-rejective nanofiltration membranes of TiO2 and Bi2S3 double-embedded Ti3C2Tx with a visible-light-induced self-cleaning ability

Abstract

To conquer the trade-off dilemma of the nanofiltration membranes for both high permeability for water and high rejection for pollutants has long been highly concerned. In this work, TiO2 and Bi2S3 nanoparticles were evenly dispersed successively into the interlayers of Ti3C2Tx nanosheets, and then filtered onto cellulose acetate support membranes. The as-obtained composite membranes exhibited a maximum water flux of 374.4 L m−2 h−1 bar−1, and a high rejection ratio for RhB, GR, MB and BSA at 97.8–100%, apparently higher than those of the Ti3C2Tx and the related membranes in literature. Such a high separation capacity was found quite stable for various dye-containing aqueous solutions, even in a high salinity environment of 5 wt% NaCl. Interestingly, 25% NaCl salt was also rejected accompanying the almost complete rejection of dye pollutants. After the filtering process, the membrane fouling of fouled Ti3C2Tx/TiO2/Bi2S3 membranes was verified quite lower than that of fouled Ti3C2Tx/TiO2 and Ti3C2Tx membranes. Furthermore, the flux recovery rate of the fouled composite membrane could reach 92.1% after washing under visible light, which could be ascribed to the composition of heterojunction causing the red shift of diffuse reflectance UV–vis spectra and the narrowing of the band gap. This study provides a new idea for the preparation of highly permeable and rejective nanofiltration membranes, and lays a foundation for its high-capacity dye removal applications.