Robust GQDs Modified Thermally Reduced Graphene Oxide Membranes for Ultrafast and Long-Term Purification of Dye-Wasted Water

Graphene-related membranes have shown promising potential for water purification. However, both high stability and efficient separation performance of graphene-related membranes for long-term operation are urgently requested for their real applications. Here, a robust graphene quantum dots (GQDs) modified thermally reduced graphene oxide (TRG) (GQDs-TRG) membrane is assembled from GQDs modified TRG aqueous dispersion. The GQDs-TRG membrane demonstrates an excellent long-term continuous separation performance in cross-flow module, with a water permeance of 2000 ± 70 L per hour per square meter per bar (LHM bar⁻¹) and 96 ± 0.2% rejection of Evans Blue (EB). The water permeance is 27 times higher than that of graphene oxide membrane and about two orders of magnitude higher than those of commercial filtration membranes with similar rejection. The gravity-driven separation experiments on a dead-end setup and nonequilibrium molecular dynamics simulation further confirm the surface cross flow is beneficial to enhancing the durability of GQDs-TRG membrane on cross-flow system. On gravity-driven separation system, under 10 cm liquid column, the GQDs-TRG membrane (2.34 µm thickness and 12.56 cm² effective area) exhibits a water permeance of 800 ± 30 LHM bar⁻¹, EB rejection above 95 ± 0.4%, and durability more than 7 month operation. These GQDs-TRG membranes show the great potential for the long-term purification of dye-wasted water with high stability and suitability.