Preparation and catalytic performance of Fe(III)-citric acid-modified cotton fiber complex as a novel cellulose fiber-supported heterogeneous photo-Fenton catalyst

Woven cotton fabric was first modified with citric acid by a conventional pad-dry-cure process and then coordinated with Fe(III) ions to prepare a Fe(III)-modified cotton fiber complex. After the characterization by SEM, FTIR, XPS, XRD and DRS, this complex was used as a heterogeneous Fenton catalyst for the degradation of a typical textile dye, Acid Red 88, under visible irradiation. Some factors affecting the modification process, such as the citric acid and NaH₂PO₄ concentrations as well as the curing temperature, were also investigated with respect to the coordinating performance of the modified fabric and the catalytic activity of its Fe complex. The results indicated that cotton fabric could be esterified with citric acid to impart the carboxylic groups, which successfully reacted with Fe(III) ions to form the complex. Dye degradation was significantly accelerated by the presence of the complex under visible irradiation. Increasing the concentrations of citric acid, NaH₂PO₄ or the curing temperature enhanced the carboxyl group content of the modified fiber as well as Fe content and catalytic activity of its complex. However, an excessive amount of citric acid and NaH₂PO₄ or a curing temperature higher than 140 °C reduced the Fe content and catalytic activity of the complex. A higher initial H₂O₂ concentration promoted the dye degradation. The excellent catalytic and mechanical performance was also found in its reuse processes.