Abstract: High-purity tannic acid was prepared from industrial tannic acid by the methods of membrane separation and modified activated carbon pretreatment. Effects of factors such as solution concentration, operation pressure difference, solution temperature on result of membrane separation were studied. Optimum conditions are as follows: solution concentration 15%(mass fraction),operation pressure difference 0.1 MPa for ultrafiltration membrane (molecular mass cut-off 6000) and 0.08 MPa for nanofiltration membrane (MMCO 600), solution temperature 40℃.In order to enhance activated carbon absorption properties, modification of granular activated carbon with nitric acid was also explored. Experimental results showed that technology of membrane separation promoted the content and yield of tannic acid significantly, which reached 97.3% and 84.7% respectively.

Key words: high-purity tannic acid, membrane separation, modified activated carbon