Evaluating the Sorption Affinity of Low Specific Activity 99Mo on Different Metal Oxide Nanoparticles

Abstract

99Mo/99mTc generators are mainly produced from 99Mo of high specific activity generated from the fission of 235U. Such a method raises proliferation concerns. Alternative methods suggested the use of low specific activity (LSA) 99Mo to produce 99mTc generators. However, its applicability is limited due to the low adsorptive capacity of conventional adsorbent materials. This study attempts to investigate the effectiveness of some commercial metal oxides nanoparticles as adsorbents for LSA 99Mo. In a batch equilibration system, we studied the influence of solution pH (from 1–8), contact time, initial Mo concentration (from 50–500 mg∙L−1), and temperature (from 298–333 K). Moreover, equilibrium isotherms and thermodynamic parameters (changes in free energy ΔG0, enthalpy change ΔH0, and entropy ΔS0) were evaluated. The results showed that the optimum pH of adsorption ranges between 2 and 4, and that the equilibrium was attained within the first two minutes. In addition, the adsorption data fit well with the Freundlich isotherm model. The thermodynamic parameters prove that the adsorption of molybdate ions is spontaneous. Furthermore, some investigated adsorbents showed maximum adsorption capacity ranging from 40 ± 2 to 73 ± 1 mg Mo∙g−1. Therefore, this work demonstrates that the materials used exhibit rapid adsorption reactions with LSA 99Mo and higher capacity than conventional alumina (2–20 mg Mo∙g−1).