The Degradation of Indigo Sodium Disulphonate by Chromium Isomorphic Replacement in Magnetite

This study was designed to investigate the degradation of indigo sodium disulphonate (ISD, a kind of indigoiddyes) in heterogeneous Fenton system (H₂O₂/Fe_3‐xCr_xO₄). The co‐precipitation was employed to synthesize a series of Cr‐doped magnetite. The result of XRD indicated that Chromium isomorphic replacement will not cause significant changes in the structure of the magnetite. The thermogravimetric (TG) and differential scanning calorimetry analysis was applied in the samples. The adsorption data showed that strong acidic condition and high concentration Cr‐containing magnetite contributed to the enhancement of adsorbing capacity. The degradation experiment was carried out in consideration of 4 aspects, including pH, Fe_3‐xCr_xO₄, H₂O₂ concentration and catalyst dosage, stating that Cr‐doped magnetite made for degrading indigo sodium disulphonate.