Synthesis of a Magnetic Fe3O4/RGO Composite for the Rapid Photo-Fenton Discoloration of Indigo Carmine Dye

In the last years, dye wastewater pollution became a major problem due to its toxicity and environmental restrictions. Indigo carmine is an indigoid dye that is largely used, and it is known by its toxicity and stability. In this work, we synthesized a magnetite/reduced graphene oxide (Fe3O4/RGO) composite with approximately 90%wt of Fe3O4 and used in the indigo carmine dye photo-Fenton discoloration (accompanied by UV–Vis spectrometry analysis). By using scanning electron microscopy (SEM), X-ray diffractometry (XRD), Laser Raman Spectroscopy (LRS), Magnetization Curves (VSM), and X-ray photoelectron spectroscopy (XPS) analyses it was observed that Fe3O4 particles of ~ 21 nm were successfully anchored on reduced graphene sheets. Zeta potential showed that the Fe3O4/RGO composite has a less negative electrostatic behavior in ultrapure water (− 46.9 mV) than the bare RGO (− 77.7 mV), promoting the attraction of indigo carmine molecule. Magnetic studies proved the ferromagnetic character of the composite with a saturation magnetization of 43 emu/g, thus promoting the easy separation from the reaction medium. In the first 5 min of reaction with the composite, the solution was completely discolored. The composite was recovered, and its reuse also showed total discoloration in the first 30 min of reaction. After first indigo carmine discoloration cycle, XPS results showed that Fe3+/Fe2+ atomic ratio was maintained, which can explain the total discoloration in the second cycle.