The collagen fiber immobilized tannins and their adsorption behaviors for heavy metal ions

As a kind of novel adsorption material, collagen fiber immobilized tannin has promised to be an effective adsorbent for removing heavy metal ions from water. The observation of this paper shown that the immobilized condensed tannins were effective in adsorbing Au(III), Th(IV), Cu(II), Pb(II), Cd(II) and Hg(II) from water. For some metal ions, like Au(III) and Hg(II), their adsorption capacities on collagen fiber immobilized tannins were very high, reaching 1500mgAu/g and 198mgHg/g respectively under proper conditions. The adsorption isotherms of Cu(II), Pb(II), Cd(II) and Hg(II) could be well described by the Freundlich model. But, for the adsorption of Au(III) and Th(IV), the adsorption isotherms could be well described by the Langmuir model. The adsorption kinetics data of Cu(II), Au(III), Hg(II) and Th(IV) could be well fitted by the pseuo-second-order model whilst for that of Pb(II) and Cd(II), no suitable model had been found. These facts suggest that different adsorption mechanisms might be involved in the adsorption processes of these metal ions. The immobilized tannins presented excellent column adsorption properties for metal ions, and the adsorption column could be easily regenerated by using diluted acid solution except for the column adsorbing Au(III).