Tunable Graphene Oxide Nanofiltration Membrane for Effective Dye/Salt Separation and Desalination

Effective dye separation and desalination are critical for the treatment of highly saline textile wastewater with dye mixtures. In this study, a graphene oxide (GO) membrane with a tunable interlayer distance (d) was fabricated to generate clean water via two-stage filtration, namely, the dye/salt separation and desalination stages. In the first stage, under low pressure (e.g., 0.3 MPa), the membrane with a d value of ca. 7.60 angstrom was suitable for removing the dye from the saline wastewater. The dye and salt (i.e., Na2SO4) rejection rates of >99% and <6.5% were achieved, respectively, indicating the significant potential to recycle the dyes from the highly saline dye wastewater. In the second stage, under a higher pressure (e.g., 0.8 MPa), the d value was reduced to ca. 7.15 angstrom, bestowing the membrane with a desalination function. The desalination rate of a single filtration process could reach up to 51.8% from 1.0 g/L saline (i.e., Na2SO4) water. The as-prepared membrane also exhibited excellent practical advantages, including ultrahigh permeability, significant antifouling (against dye) performance, and excellent stability. Furthermore, with the stacking of multistage filtration systems, the proposed membrane technology will be capable of regenerating dye and producing clean water.

Automated summary

In this study, a graphene oxide membrane with tunable interlayer distance was fabricated for effective dye separation and desalination in saline textile wastewater treatment. The membrane achieved high dye rejection rates (>99%) and low salt rejection rates (<6.5%) in the first filtration stage, while demonstrating a desalination rate of up to 51.8% in the second stage. The membrane also showed excellent practical advantages such as high permeability, antifouling performance, and stability, with the potential for regenerating dye and producing clean water through multistage filtration systems.