Comparative study of un-doped CeO ₂ and metal (Mn, Co, Fe)-doped CeO ₂ nanostructures for the removal of golden yellow dye from synthetic wastewater

In this study, the activity of un-doped cerium oxide (CeO2) nanostructure with metal (Mn, Co, Fe)-doped CeO2 nanostructures was compared as effective scaffolds for the elimination of Golden Yellow (GY) Dye. For this purpose, the un-doped and doped-CeO2 nanostructures were prepared through co-precipitation treatment and characterised using the following techniques like FTIR, XRD, UV, PL, SEM and EDX analysis. The synthetic nanostructures were selected for the removal of GY through adsorption and photocatalytic degradation from wastewater. Tauc's model was employed to determine the optical band gap, and various key parameters (contact duration, pH, nanostructure dosage and GY concentration) were optimised for the adsorption/photocatalytic degradation of GY. The adsorption and degradation processes for these nanostructures were found to be pH-dependent, with an optimum pH value of 4. UV–visible spectroscopy was employed to probe the GY adsorption followed by the GY degradation, revealing a higher removal and degradation efficiency of 39.89% and 58.46% for Mn-CeO2, 34.60% and 47.21% for Co-CeO2 and 31.67% and 39.10% for Fe-CeO2 compared to 14.05% and 30.37% for un-doped CeO2, respectively. In total, 98.35% of GY removal was achieved by Mn-CeO2 compared to 44.42% by un-doped CeO2 within 175 min via adsorption (50 min) followed by degradation (125 min). Additionally, the absorption mechanism underwent analysis, with the kinetic data aligning closely with the pseudo-first-order model. Examination of the adsorption capacity at various equilibrium concentrations of the dye solution revealed the formation of monolayers and chemisorption phenomena. Moreover, the rate constant dropped when scavengers like ethylenediaminetetraacetic acid (EDTA), isopropyl alcohol (IPA), and hydrogen peroxide (H2O2) were added because they capture holes (h+), hydroxyl radicals (·OH), and superoxide radicals (·O2−) respectively, with EDTA showing more prominent effects.