High-performing composite membrane based on dopamine-functionalized graphene oxide incorporated two-dimensional MXene nanosheets for water purification

With unique structural and physicochemical properties, the upcoming two-dimensional (2D) materials have become promising candidates for the design and fabrication of high-performance membranes. In this work, for the first time, the dopamine-functionalized graphene oxide (DGO) nanosheets were intercalated into the MXene (Ti3C2Tx) nanosheets, and subsequently, a series of novel DGO/MXene composite membranes were prepared via vacuum filtration on hydrophilic polyvinylidene fluoride (PVDF) membranes as the support layer. The effect of mass ratios between DGO and MXene on the resulting membrane structure and overall performances were systematically investigated in detail. Incorporation of DGO increased the mechanical stability of composite membrane, but reduced its interlayer spacing. The most suitable composite membrane, M4 (MXene: DGO = 1:2) with nearly 2 mu m thickness of functional layer, exhibited an excellent dye rejection ratio 98.1% (for Direct Red 28) and 96.1%( for Direct Black 38) as along with a high value of water flux (63.5 Lm(-2) h(-1)) at a pressure of 0.1 MPa, compared with the pure MXene and DGO membranes. Furthermore, molecular dynamics (MD) simulation indicated that the permeation rate of water molecules across the active layer was directly determined by the interlayer spacing of nanosheets. Additionally, composite membrane M4 displayed a relatively low rejection ratio of differently charged salts (9.7% for Na+) and (4.3% Mg2+).

Automated summary

In this study, novel DGO/MXene composite membranes were prepared and the most suitable membrane, M4, exhibited excellent dye rejection ratio and high water flux value compared to pure MXene and DGO membranes. Molecular dynamics simulation revealed that water permeation rate was directly determined by interlayer spacing, and M4 also showed relatively low rejection ratios for differently charged salts.