Comparative study of different Fe(III)-carboxylic fiber complexes as novel heterogeneous Fenton catalysts for dye degradation

Three carboxylic fibers including alginate fiber, polyacrylic acid-grafted polypropylene (PP), and polytetrafluoroethylene (PTFE) fibers were coordinated with Fe(III) ions, respectively, to prepare the different Fe(III)-carboxylic fiber complexes. On the basis of investigating their coordination with Fe(III) ions, the coordination number, surface morphology, and light adsorption property of the formed Fe(III)-carboxylic fiber complexes were characterized and compared. And the catalytic performance of the three complexes was then evaluated as the heterogeneous Fenton catalysts in the degradation of a typical azo dye, Reactive Red 195 in water. The results indicated that alginate fiber could react with Fe(III) ions more easily than the grafted PP or PTFE fibers containing similar amount of carboxyl groups to form Fe(III)-carboxylic fiber complexes. Higher concentration of Fe(III) ions led to a proportional increase in Fe content of the obtained complexes. Fe(III)-alginate fiber complex has the more unsaturated configuration than Fe(III)-grafted PP or PTFE fiber complex due to the changes in its coordination number. Moreover, the light adsorption of the complexes was affected by nature of fiber used. The incorporation of hydrophobic synthetic fiber, especially grafted PTFE fiber reduced the visible light absorption of the obtained complexes. Three Fe(III)-carboxylic fiber complexes could catalyze the dye degradation in the dark or under light irradiation. Fe(III)-alginate fiber complex showed better catalytic activity and reuse stability than the other two complexes with similar Fe content.