Functionalization of wood fibers based on immobilization of tannic acid and in situ complexation of Fe (II) ions

Tannin is often used as a heavy metal adsorption material, and the formation of complex between tannin and metal ion has a certain porous structure. Based on this, in this paper, wood fibers were used as the matrix to immobilize tannic acid, and then Fe (II) ions in aqueous solution were adsorbed in situ to modify some properties of wood fibers. The results showed that the higher the concentration of tannic acid, the more iron complexes immobilized on the wood fibers. These complexes could fill the pores of wood fibers, increase the specific surface area and enhance the moisture absorption. However, too many complexes could cluster, reducing the surface area. On the other hand, the complexes greatly reduced the number of hydroxyl groups on the fiber surface, making the surface hydrophobic. The complexes also could effectively reduce the pyrolysis temperature of wood fibers and increase the amount of residue char. Therefore, through such a simple two-step green treatment, it can not only remove some Fe (II) ions from water, but also modify the porosity, hydrophobicity and thermal stability of wood fibers.