Graphite oxide/boron nitride hybrid membranes: The role of cross-plane laminar bonding for a durable membrane with large water flux and high rejection rate

Swelling of graphene oxide (GO) membrane greatly restricts its use in liquid separation applications. Cross-linking is widely used to stabilize GO membrane but often results in enlarged d-spacing. This work presents a durable hybrid GO/boron nitride membrane with both physical confinement and chemical bonding, which simultaneously achieves large water flux and excellent dye rejection rate. By alternating GO nanosheets and amino-modified boron nitride (a-BN) nanosheets in the hybrid membrane (a-BNGO) structure, plane-plane conformation and edge-edge covalent bonding facilitate the formation of tightly packed laminar structure, which is demonstrated efficient to restrict membrane swelling, improve water flux and methylene blue (MB) separation performance. Specifically, a-BNGO hybrid membranes, with a-BN/GO mass ratio ranging from 1:4 to 2:1, were prepared by pressurized filtration method on top of polydopamine coated polyethersulfone (PDA/PES) substrate. By optimizing the a-BN/GO ratio, high rejection rate of 99.98% and large water flux of 4.15 LMH can be achieved. The separation properties of these membranes were tested stable for up to 9 h, even in different pH conditions (pH = 4–10).