A new method for preparing α-alumina ultrafiltration membrane at low sintering temperature

α-Al₂O₃ has attracted much attention owing to its excellent organic solvent resistance and acid-base corrosion resistance. However, the preparation of α-Al₂O₃ ultrafiltration membranes by sol-gel method is still a challenge, because the formation of α-phase requires high temperature calcination and is accompanied by rapid grain growth. To reduce the phase transition temperature and obtain smaller grains, we started from a polymeric sol with particle size of approximately 3.7 nm, which was converted into α-Al₂O₃ at a low temperature of 1000 °C. Moreover, graphene oxide (GO) as the sacrificial layer was used to prevent the sol from penetrating into the macroporous support, and to obtain a high permeability α-Al₂O₃ ultrafiltration membrane. Because GO can be pyrolyzed at temperature above 500 °C, an ultra-thin and high pure water permeability α-Al₂O₃ ultrafiltration membrane was obtained at a low temperature of 1000 °C. The prepared α-Al₂O₃ ultrafiltration membrane showed a pure water permeability of up to 390 L m⁻² h⁻¹ bar⁻¹ and a pore size of approximately 20 nm.