Aminated polyacrylonitrile fibers for humic acid adsorption: behaviors and mechanisms

Aminated polyacrylonitrile fibers (APANFs) were prepared by surface modification of polyacrylonitrile fibers (PANFs) with diethylenetriamine in a solution, and the APANFs were studied as an adsorbent for humic acid removal in a series of batch adsorption experiments. The surface modification reaction introduced the amine groups on the surface of the fibers, and the APANFs had a zero point of zeta potentials at pH 8.1, in contrast with pH 3.5 for the PANFs. Adsorption experiments indicated that the APANFs were very effective in removing humic acid from aqueous solutions in the pH range of 2-10, whereas the PANFs did not adsorb humic acid at all under the same conditions. It was found that both electrostatic interaction and surface complexation mechanisms played important roles in humic acid adsorption on the APANFs, although the relative importance of each of the adsorption mechanisms varied with solution pH values. With the advantages of large specific surface areas and enhanced reactive surface properties, the APANFs have great potentials in water treatment for the removal of humic substances and other polarized or electrically charged species.