Ultrafast fabrication of uniform nanoporous α-alumina membranes by photothermal-enhancing

Ceramic ultrafiltration membranes have attracted significant attention in bioproduct manufacturing due to their excellent biocompatibility and durability. However, traditional fabrication process involves high temperatures and prolonged heat treatments, which results in grain growth, particle sintering, and pore coalescence, eventually affecting separation efficiency. This study proposes an ultrafast fabrication method through the photothermal-enhanced rapid thermal process. By doping alumina sol with iron element, light-absorbing intensity can be increased by 7–21 times, significantly enhancing its photothermal effect under near-infrared radiation and shortening the heat treatment cycle. Additionally, the α-Fe₂O₃ formed during calcination promoted α-Al₂O₃ transition via a heterogeneous nucleation mechanism, effectively suppressing grain growth and sintering. Under optimized conditions —a heat treatment cycle of 115 s and a temperature of 850 °C—α-Al₂O₃ tight ultrafiltration membranes were rapidly fabricated. The membrane exhibited a dextran molecular weight cutoff (MWCO) of 13.9 kDa and a pure water permeability of 220 LMH/bar. In enzyme-membrane coupling tests, the membrane demonstrated precise permeation of bioactive peptides with molecular weights between 200 and 1700 Da (>98 wt%) while retaining peptides with molecular weights exceeding 2200 Da.