Cerium oxide nanoparticles for color removal of indigo carmine and methylene blue solutions

In this work, CeO2 nanoparticles (NPs) were synthesized by sol-gel method, characterized and used for color removal of indigo carmine and methylene blue dye solutions under visible light. The structural properties and crystallinity of NPs were determined by X-ray diffraction (XRD) and a cubic phase of ceria with 13.5 nm crystallite size was confirmed. In addition, the morphology was studied by using Scanning Electron Microscopy (SEM) and a semi-spherical morphology was observed. The surface chemical analysis of CeO2 NPs was performed by using an X-ray photoelectron spectroscopy (XPS), and the presence of functional groups and the absorption spectra in CeO2 NPs were investigated by Fourier-transform infrared spectroscopy (FTIR) and by UV-vis spectroscopy, respectively. The experimental results showed that the highest color removal was obtained for indigo carmine (≈ 90% at pH 2.5 within 180 min). Thus, CeO2 NPs may be suitable for removal of anionic dye effluents at room temperature.