Activation of Na₂S₂O₈ for dye degradation by Fe complexes fixed on polycarboxylic acids modified waste cotton

Three aliphatic polycarboxylic acids (PCAs) including tartaric acid (TA), citric acid (CA) and 1,2,3,4-butanetetracarboxylic acid (BTCA) were used for the surface modification of waste cotton fiber by an industrialized pad-dry-cure process to introduce carboxyl groups, which then coordinated with Fe³⁺ ions to obtain three PCA modified cotton fiber Fe complexes. TA modified cotton fiber could easily react with Fe³⁺ ions to form its complex with high Fe content. Furthermore, TA modified cotton fiber Fe complex showed a better enhanced effect of activated Na₂S₂O₈ to produce free oxygen radicals for the degradation of an azo dye, Reactive Red 195 than the other two complexes. Different critical Fe contents were found for three complexes to obtain the best enhanced effect.