Construction of self-cleaning gradient multilayer TiO2 coating on Al2O3 hollow fiber membrane for enhanced gelatin purification

Gelatin, a natural protein, is extensively used in the food, pharmaceutical, and cosmetics industries. However, purifying gelatin to meet the specific requirements of various industries remains a considerable challenge. Ceramic membrane separation technology, renowned for its high permeability, excellent anti-fouling properties, and long lifespan, has been widely applied in the food, biotechnology, and water purification industries. In this study, a sol-gel method was employed to fabricate a gradient multilayer TiO 2 -modified coating on the surface of an α-Al 2 O 3 porous ceramic membrane. The viscosity of the TiO 2 sols was adjusted by varying the concentrations of polyethylene glycol (PEG 2000) and aging times. The results indicated that coating the C-P5^5 composite membrane with a sol containing 5 wt% PEG, aged for different durations (2, 5, 10, 15, and 18 d), effectively reduced the weight-average molecular weight ( M w ) of the permeate from the feed solution of 52.4 kDa–11.9 kDa. However, the C-P10^5 composite membrane, with a 10 wt% PEG content and aged for the same durations, yielded a permeate gelatin M w of 13.6 kDa. The composite membrane with excellent anti-fouling and photocatalytic self-cleaning properties holds promise for innovative applications in gelatin purification and bio-separation processes.