Dispersive two-dimensional MXene via potassium fulvic acid for mixed matrix membranes with enhanced organic solvent nanofiltration performance

Abstract

The emerging two-dimensional (2D) MXene with high aspect ratio, hydrophilic, and abundant terminations, has been used to fabricate mixed matrix membranes (MMMs) for diverse nanofiltration applications. However, the traditional method to disperse MXene has low exfoliation efficiency accompanied by auxiliary toxic chemicals. In this work, a novel method was applied to obtain a few or monolayer MXene by using the sonication-assisted potassium fulvic acid (PFA) method for the exfoliation of bulk MXene. It not only improved the wettability of Mxene, but also increased the surface Zeta potential and enhanced the electrostatic repulsion between particles. The ultrathin MXene was then integrated into the commercial P84 polymeric matrices to fabricate MMMs for organic solvent nanofiltration (OSN) application. The as-prepared MMMs were systematically characterized by SEM, XRD, AFM, EDX, TG, mechanical properties, etc. Compared to the original P84 membrane, the u-Ti₃C₂T_x@P84 MMMs_x showed improved ethanol permeability (3.97 vs. 2.14 L m⁻² h⁻¹ bar⁻¹) without sacrificing BBR rejection (96.1 vs. 94.2%). Furthermore, the permeance showed a typical “volcano” curve with increasing u-Ti₃C₂T_x loading content, while the rejection showed a “wavy” trend. Interestingly, a substantial increase in permeance without sacrificing rejection was found when compared with bulk MXene. Moreover, the developed u-Ti₃C₂T_x@P84 MMMs with good long-term stability (up to 50 h) also exhibited excellent OSN performance in other organic solvents such as methanol, isopropanol, acetone, acetonitrile, hexane, etc. Accordingly, the dispersive MXene has great potential for OSN practical applications.