Decolorization of Reactive Red K-2BP Wastewater with Sponge Iron

The decolorization of Reactive Red K-2BP wastewater with sponge iron was investigated through batch experiments. The decolorization process appeared to a pseudo-first order reaction. The observed first-order rate constants (k_obs) varied from 0.087 to 0.033 /min with the dye concentration from 50 to 300 mg/l at 50 g/l sponge iron loading , and half-lives (t_1/2) varied from 7.97 to 21 min. The decolorization efficiency increased with increments of sponge iron dosage, and decreased with the increments of particle size of the sponge iron and initial pH of dye concentration. Under optimal conditions, over 90% of decolorization efficiency could be obtained. Comparison of UV- vis spectra of Reactive Red K-2BP before and after reaction showed disappearance of the absorbance peaks in the visible region after reaction and appearance of a new absorbance peak at 202 nm, indicating destruction of the azo bond and generation of many degradation intermediates. X-ray diffraction (XRD) of sponge iron showed magnetite (Fe+2Fe₂+3O₄) and lepidocrocite (Fe+3O(OH)) on the surface of sponge iron after the reaction.