Construction of high-performance CeO₂ ultrafiltration membrane for high-temperature dye/salt separation

CeO₂ is an alternative membrane material for precise separation under harsh conditions because of its single fluorite structure and outstanding high-temperature stability. In this study, uniform and stable CeO₂ colloidal sols were successfully prepared using an ultrasound-assisted precipitation method with an average particle size of approximately 5 nm. To prepare crack-free CeO₂ membranes with a controllable thickness, concentration of polyvinyl alcohol in the colloidal sol and the coating time were investigated. An integrated membrane layer was fabricated by adjusting the sol to PVA solution mass ratio to 1:1 with a coating time of 30 s. After calcination at 500 °C, a thin CeO₂ membrane (approximately 200 nm thick) was obtained. In addition, the CeO₂ material derived from the as-prepared sol showed a fluorite structure and lattice fringes corresponding to different crystal planes, indicating the formation of a pure CeO₂ thin membrane. The CeO₂ membrane exhibited a high performance, with a molecular weight cut-off of 3.9 kDa and a high water permeance of 100 L m⁻² h⁻¹·bar⁻¹. It showed excellent thermal stability, promising good potential applicability at high temperatures. Additionally, it exhibited the dye rejection rates of >99% for Direct Red 80 and 95.5% for Congo Red, and salt rejection rates of <1% at 60 °C in the simulated dye wastewater treatment. Overall, this study presents a new tight ultrafiltration membrane material that has good potential for high-temperature dye wastewater treatment.