Mechanisms of molybdenum ions adsorption on gamma nanoalumina: A detailed analysis using kinetics and isotherms with radiotracer techniques

The adsorption of molybdenum ions from aqueous solutions was studied using commercial nanometric particles of gamma aluminum oxide (γ-Al₂O₃) measuring 5 and 80 nm, employing the radiotracer technique, which allowed working with trace concentrations and accurately monitoring the evolution of the species in solution. To characterize the process, kinetic and equilibrium studies were carried out in order to elucidate the adsorption mechanism and determine the maximum capacity. The results showed that the retention of molybdenum ions in γ-Al₂O₃ is rapid, occurring mainly in the first two minutes, and that the temporal evolution is adequately described by the pseudo-second-order model, indicating specific interactions between the molybdate anion and the alumina surface. The 5 nm γ-Al₂O₃ material showed a slightly higher adsorption capacity than the 80 nm γ-Al₂O₃, attributable to its larger specific surface area. According to the isothermal model, the maximum adsorption values ( q m ) were 386.95 mg g⁻¹ for γ-Al₂O₃-5 nm and 368.20 mg g⁻¹ for γ-Al₂O₃-80 nm. These results demonstrate the high efficiency of γ-Al₂O₃ nanomaterials in molybdenum adsorption and highlight their potential application in ⁹⁹Mo/⁹⁹ᵐTc generator systems. • Nanometric γ-Al₂O₃ (5 and 80 nm) evaluated as adsorbents for molybdenum ions by radiotracer technique. • Adsorption was rapid in the first few minutes and fit the pseudo-second-order kinetic model. • Freundlich isotherm best described the equilibrium data, indicating heterogeneous active sites. • Maximum adsorption capacities of 386.95 mg g⁻¹ (5 nm) and 368.20 mg g⁻¹ (80 nm) were achieved.