Enhanced stability and separation efficiency of graphene oxide membranes in organic solvent nanofiltration

Abstract

Graphene oxide (GO) membranes have been extensively reported for nanofiltration in water system, but their applications in organic solvent nanofiltration (OSN) are rarely studied. The instability of GO membranes in solvents seriously impedes their practical applications. Thus, it is highly desirable to fabricate GO membranes with excellent stabilities for OSN. Herein, we report GO membranes crosslinked with boronic acid polymer (BA) for this purpose. These membranes exhibited strong tolerance to various organic solvents, favorable stability and OSN performances. The rejection for acid fuchsin (AF) methanol solution of the GO membrane (mass loading = 44 mg m⁻²) was increased by 20.7% upon addition of 0.5 BA polymer molecules (weight ratio of BA to GO). The optimized membrane maintained high rejection (95.8%) for AF methanol solution with a slight compromise in methanol permeance even after being soaked in water for one month. Moreover, the composite membrane exhibited high rejections for both EB and AF in harsh DMF solvent. As a demonstration, it showed high rejection for vitamin B12 (VB12) of 99.0% with a methanol permeance of 3.94 L m⁻² h⁻¹ bar⁻¹.