TiO2-ZrO2 nanofiltration membrane for efficient decolorization of long-chain dicarboxylic acids

Long-chain dicarboxylic acids (LCDAs) are important basic chemical raw materials, and their bio-synthesis has gained increasing prominence in recent years. However, the pigments formed during the biological process have a significant impact on the purity of the product. In this study, a TiO 2 -ZrO 2 ceramic nanofiltration (NF) membrane with tunable pore size was developed and used for efficient decolorization of LCDA fermentation broth. Based on the inhibitory effect of Ti doping on ZrO 2 phase transition, combining the steric hindrance effect of organic residues, NF membranes with regulable molecular weight cut-off (600/1100/1600 Da) can be achieved by controlling calcination temperature in range of 350–450 ℃. They all have a rejection of over 98.8 % for the larger molecular weight pigments (DY9, AY3 and AY23), and the rejection for the smaller SY pigment is also above 90 %. In addition, the NF membranes exhibited excellent performance in crude sebacic acid aqueous solution. With a sebacic acid salt rejection of less than 5 % and a pigment rejection of over 90 %, they achieved simultaneous efficient decolorization and product recovery. Finally, the multi-channel NF membrane prepared at 400 ℃ calcination temperature achieved excellent decolorization performance in the real dodecanedioic acid fermentation broth, increasing the purity of acid after acidification crystallization from 98.62 % to 99.56 %. This verified its application potential in the industrial treatment of LCDA fermentation broth.