Preparations Of Adsorbents Based On Collagen Fibers And Investigations Of Their Adsorption Characteristics

Animal skins, the byproduct of domestic animals consisting of 90% collagen, are the most abundantly reproducible animal biomass resource. On the basis of collagen fibers, two novel adsorption materials were prepared by ingeniously utilizing the principles of protein chemistry, leather chemistry, vegetable tannin chemistry and chemical engineering. One of them was designed for the purpose of selectively removing tannins from Chinese medicinal herbs extracts. Another was for removing heavy metal ions from water. The methods and mechanisms of preparing the materials were studied and their adsorption characteristics were extensively investigated.In the first part of this thesis, the adsorbent used for highly selective removal of tannins from Chinese medicinal herbs extracts or injections was prepared by the reaction of bovine skin collagen fiber and glutaraldehyde, named collagen fiber adsorbent. Tea polyphenols and tannic acid were selected as probe molecules to investigate the adsorption characteristics of the collagen fiber adsorbent to plant polyphenols. It was found that the adsorption extent of plant polyphenols on collagen fiber adsorbent was determined by both molecular size and structure. The components that have bigger molecular size or pyrogallol structure in molecule exhibit higher adsorption extent.Then, typical active constituents of Chinese medicinal herbs, including baicalin, synphnine, puerarin, naringin, genistin and genistein, were selected as probe molecules to investigate adsorption selectivity of collagen fiber adsorbent to tannins. Results showed that, in the mixed solutions of active constituents and hydrolysable tannin(tannic acid), the adsorption extent of tannic acid by the adsorbent was > 97%, while the adsorption extent of active constituents was limited. In the mixed solutions of active constituents and condensed tannins, the adsorption extent of condensed tannins was 100%, while that of active constituents was also limited except a few constituents. The adsorption extent of active constituents in the solutions without tannins was always higher than that in the solutions containing tannins, which indicates the advantage of tannins in the competition adsorption. It was also observed that the collagen fiber adsorbent could remove polymer procyanidins (condensed tannins) from procyanidins solution, while the oligomer procyanidins that are of biological activity were retained in the solution, which remarkably shows that the adsorption selectivity of collagen fiber adsorbent is related to molecular size of components. Polyamide is generally used for the removal of tannins, but its adsorption selectivity was inferior to collagen fiber adsorbent in comparison experiments. Therefore, this novel adsorbent promises a new and effective approach for selective removal of tannins from plant extracts.In addition, a series of the collagen fiber adsorbents were prepared by using formaldehyde, Cr3+, Zr4+ and Ti4+ as cross-linking agents respectively. The adsorption characteristics of these adsorbents to the active constituents and tannins were investigated. It was found that the adsorption selectivity of formaldehyde cross-linked collagen fibers to hydrolysable tannins was nearly the same as that of glutaraldehyde cross-linked collagen fibers, but its adsorption selectivity was relatively poor for some condensed tannins (such as larch tannin). The adsorption selectivities of Cr3+, Zr4+ and Ti4+ cross-linked collagen fibers were inferior to that of glutaraldehyde cross-linked collagen fibers. The active constituents would be remarkably lost at the same time of removing tannins.Based on the experimental results above, the adsorption characteristics of glutaraldehyde cross-linked collagen fiber adsorbent were further investigated. The influences of adsorbent amount, adsorption time and organic solvent content in solution on the adsorption of active constituents and tannins were studied. It was found that the optimum amount of adsorbent was 0.3g when 100ml solution with tannin content 1000mg/L was treated. Wi...