NaA zeolite-coated meshes with tunable hydrophilicity for oil-water separation

NaA zeolite was fabricated on a stainless steel mesh by secondary growth method through optimizing aluminum/silicon ratio (ASR) to effectively separate oily water. The NaA zeolite-coated mesh with the highest superoleophobic property had an ASR of 1.21 and an oil contact angle of 163.7°. The highest membrane flux obtained was 13,513 L m^-2 h⁻¹ for an ASR = 0.91 and the highest separation efficiency was 99.5% for an ASR = 1.21. NaA zeolite meshes were recycled and reused for 15 cycles by rinsing the membrane with DI water between each test. The oil rejection rate of the mesh for ASR = 0 decreased approximately 2.7% after 4 cycles of separation, but the oil rejection rate of the meshes for ASRs = 0.3–182 did not change with 4 cycles of oil water separation, which is attributed to the uniformity of the NaA zeolite coating and its thermal stability. For long-term usage, the NaA zeolite meshes were regenerated by re-calcination, with an average oil rejection rate after three cyclic calcinations of more than 99.3%. In hot and corrosive solutions, the NaA zeolite meshes were stable, showing oil rejection rates above 99.3%. NaA zeolite meshes were also used for separation of various oils, such as n-hexane, mineral oil, olive oil, and diesel. The oil rejection rates were higher than 98.3% in all cases, which demonstrates that NaA zeolite mesh is very promising technology for oil/water separation applications.