Aramid Nanofiber Membranes Reinforced by MXene Nanosheets for Recovery of Dyes from Textile Wastewater

Efficient recovery of dyes from textile wastewaters using membrane-based technologies calls for membranes with low rejection of salts but high rejection of dyes. In this study, we intercalated the rigid 2D-ultrathin MXene (Ti3C2Tx) nanosheet into the loose framework assembled by 1D aramid nanofibers and obtained a MXene-reinforced aramid nanofiber (ANF) membrane. The optimized MXene-reinforced ANF membrane (20 wt % MXene loading) exhibited a high selectivity of dye/salt, that is, 99.1 ± 0.3% for Alcian Blue, 96.1 ± 2.4% for Congo Red, 98.6 ± 0.9% for Rose Bengal, and extremely low rejection of salts (<0.2%) at a concentration of 5 g L–1 of NaCl with separation factors of 826, 1068, and 758 for Alcian Blue, Congo Red, and Rose Bengal, respectively. Moreover, the membrane permeability could reach 195.3 ± 6.5 L m–2 h–1 bar–1. The MXene-reinforced ANF membrane demonstrated a superior separation performance to most of the other reported membranes for dye/salt fraction. Mechanistic investigation showed that the reinforced rigidity of the membrane by the intercalated MXene was the main mechanism for the enhanced permeability and selectivity of the MXene/ANF composite membrane (that is, a nanochannel of 2.34 nm was maintained for the MXene/ANF composite membrane after filtration while the nanochannel of the ANF membrane was increased from 2.27 to 2.43 nm). The results highlight that the nanofibrous membranes reinforced by rigid 2D materials are promising for an effective separation of dyes and salts in textile wastewaters.