Selective adsorption of vegetable tannins onto collagen fibers

Vegetable tannins are widely distributed in the plant kingdom. In many cases, it is necessary to remove tannins from natural beverages and medicinal plant extracts due to their physiological toxicity. In the present work, an adsorbent for this purpose was prepared on the basis of hide collagen fibers. Its adsorption selectivity for tannins was studied, using tannic acid as a target component to be removed and tea polyphenols, isoflavones, and baicalin as probe molecules. The experiment results showed that hide collagen fiber is able to remove polyphenols containing the galloyl group from aqueous solution effectively, and the extent of adsorption for tannic acid is almost 100%, while slightly adsorbing probe molecules. As a comparison, the adsorption property of macroreticular resin which was usually suggested to be used for removal of tannins was also investigated. It showed no significant adsorption selectivity in the present experiments. The mechanism of adsorption selectivity of collagen fibers for tannins was also discussed.