Scalable concentration process of graphene oxide dispersions via cross-flow membrane filtration

Fundamental research on developing a facile, industrially viable approach for producing concentrated single-layered graphene oxide (GO) aqueous dispersions is crucial for applications in related industrial fields. In this innovative work, cross-flow membrane filtration is reported for the first time for preparing stable GO dispersions with concentrations controlled from 1 to 16 g·L⁻¹. The flux behavior with different process conditions (membrane pore diameter, transmembrane pressure, and tangential velocity), the relevant hydraulic resistances, and fouling mechanism have been systematically studied for optimization of the process parameters. The physicochemical properties of GO products are characterized by various methods, and the results show that all the concentrated dispersions possess good fluidity, with hydrolysis of functional groups resulting in a pH decline, and no re-stacking or agglomeration of the GO sheets occurring during the concentration process. The concentrated GO dispersions, presenting distinctive liquid crystal phases, offer tremendous potential in the fabrication of highly ordered macroscopic structures as well as the development of novel graphene-based devices.