Highly Porous Ceria as an Adsorbent for Removing Artificial Dyes from Water

The aim of this manuscript is to produce highly porous ceria in easy-to-handle microspheres via a hard template method using the short-chain alcohol as an effective solvent of the cerium oxide precursor. Additionally, the ceria has been investigated as an adsorbent for selected artificial dyes from aqueous solutions. The synthesis relied on the calcination of Amberlite XAD7HP saturated with methanolic cerium(III) nitrate hexahydrate solution in air. The product was characterised using scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, and X-ray Photoelectron Spectroscopy. The low-temperature adsorption/desorption method was used to estimate parameters characterising the overall porosity of the product. The adsorption of selected dyes, including Brilliant Blue FCF (E133), Cochineal Red A (E124, Ponceau 4R), Tartrazine (E102), Methylene Blue (MB), and Methyl Orange (MO) from aqueous solutions was investigated with the UV–Vis spectrometer via the static adsorption experiment. The ceria microspheres with a specific surface area exceeding 180 m² g⁻¹ were found to be composed of nanocrystals whose size did not exceed 9 nm, as indicated by XRD and TEM. On the surface of ceria, the atomic percentage of Ce³⁺ determined by XPS was 17%. The ceria could adsorb from 13 μmol g⁻¹ to 33 μmol g⁻¹ of dyes (E102, E124, E133, MO) from water. The hard template method can produce highly porous ceria that could be used in environmental protection.

• Mesoporous cerium oxide with a specific surface area of 187 m² g⁻¹ has been fabricated.

• The ceria is in the form of microspheres with a ‘unusual’ Ce³⁺ to Ce⁴⁺ ratio of 17:83.

• The ceria can adsorb from 13 μmol g⁻¹ to 33 μmol g⁻¹ of dyes from water.