Abstract: The coordination process and structure between amidoxime modified polyacrylonitrile (AO-PAN) fiber and FeCl3 in aqueous solution were studied by using X-ray photoelectron spectroscopy (XPS), Fourier transforminfrared spectrometer (FTIR), dynamic thermal mechanical analyzer (DTMA), and electrical conductivity method, respectively. The coordination Fe-AO-PAN fiber was obtained, and then used as a heterogeneous Fenton catalyst for the oxidative degradation of two azo dyes including C.I. Reactive Red 195(RR 195) and C.I. Acid Black 234(AB 234) in the presence of H2O2. The catalytic function of Fe-AO-PAN on dye degradation was investigated with respect to decoloration percentage in this work. The results indicated that the Fe3+ ion of Fe-AO-PAN was coordinated with three amino nitrogen atoms and three hydroxyl oxygen atoms of three amidoxime units on the surface of AO-PAN by covalent bond, and the coordination number was six. Moreover, the oxidative degradation of two azo dyes in water was significantly accelerated in the presence of Fe-AO-PAN under light irradiation, and the azo linkages and aromatic ring of azo dye molecules were decomposed. Increasing the degree of conversion from nitrile group to amidoxime group on the surface of PAN fiber caused not only higher Fe3+ content of Fe-AO-PAN, but also its stronger catalytic performance
on dye degradation in aqueous solution.

Key words: Polymer-metal complex, Coordination structure, Modified PAN fiber, Ferric ion, Catalysis, Azo dye, Degradation