Highly stable and permeable graphene oxide membrane modified by carbohydrazide for efficient dyes separation

As natural resources become more and more limited, it is exceptionally essential to decrease energy consumption in membrane separation processes, which makes membranes with ultra-high water permeance increasingly expected. Graphene oxide (GO) membranes have exhibited an unsurpassed future for wastewater purification. However, it is two key challenges to greatly increase the water permeance while retaining the removal efficiency of contaminants and improve the enduring stability of membranes in aqueous solution. In this work, the membranes with ultrafast water permeability were prepared by self-assembly vacuum filtration method using carbohydrazide (CHZ) as reducing and cross-linking agent. The obtained lamellar rGO/CHZ nanofiltration membranes exhibited water permeance bigger than 1600 L m-2h−1 bar−1, and outstanding separation efficiency, e.g., Congo Red (CR), Malachite Green (MG), and Crystal Violet (CV) removal rate of 99%. More importantly, the composite membrane exhibited efficiently selective separation of various mixed dyes. Such as binary mixed dyes of MG/MO, the removal rate of MG is 99%, while the removal rate of MO is merely 23%. In addition, the membrane still showed excellent stability after long-term immersion in solutions of various pH values. The separation performance in terms of complete rejection of single dyes and selective filtration of mixed dyes makes them one of the promising materials for dye separation, purification, and reuse.