A versatile approach to treat aqueous residues of textile industry: The photocatalytic degradation of Indigo Carmine dye employing the autoclaved cellular concrete/Fe2O3 system

In this work, a new composite consisting of the autoclaved cellular concrete (ACC) impregnated with Fe(III) ions was prepared and evaluated as heterogeneous catalyst, in Fenton-like and photocatalytic processes, for the degradation of the textile dye Indigo Carmine in aqueous medium. One of the differentials of this new technology is that the catalytic system is less dense than water. Hence, it can be easily removed from the wastewater reservoir after finishing the treatment process. Besides density measurements, the material was fully characterized by X-ray powder diffraction (DRX), 57Fe-Mössbauer spectroscopy, surface area measurements (BET), atomic absorption spectrometry and scanning electron microscopy (SEM). The degradation of Indigo Carmine was monitored by electronic spectroscopy and the by-products characterized by direct infusion-ESI-(−)MS (electrospray ionization mass spectrometry in the negative ion mode) and MS/MS (tandem mass spectrometry). It was also verified that after four hours of treatment by the Fenton-like and photocatalytic systems mineralization rates, determined by total organic carbon (TOC) analysis, of 74% and 70% were achieved, respectively. Finally, toxicity tests, against Vero cells, indicated that the toxicity of the degradation products, generated by both processes, is smaller or similar to the precursor dye.

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► Autoclaved cellular concrete (ACC) and Fe2O3 as new catalyst for the degradation of environmental contaminates.
► Catalysts for the degradation of Indigo Carmine by Fenton-like and photocatalytic processes.
► Mineralization higher than 70% was achieved after 4 h of catalytic reaction.