Kinetics based study on sorption properties of titanium dioxide concerning 99Mo production using sulfate-based aqueous targets

Solutions of uranium salts can be used as targets for the production of medical radionuclides to exclude the most troublesome stages of solid target processing and make the targets reusable. An industrial introduction of this technology for the production of Mo-99 requires further development of the technological process of molybdenum extraction using a stable selective sorbent, such as titanium dioxide. Solutions of uranium sulfate in sulfuric acid have proven themselves well at the stage of irradiation, but the adsorption behavior of molybdenum in this media has not been studied sufficiently. A negative effect of the background concentration of the sulfate ion on the efficiency of extraction is shown in this paper, and a kinetic analysis is carried out using Morris-Weber model of intraparticle diffusion. Experiments show that the sorption kinetics can be both positively and negatively affected by an increase in pH from 1.3 to 2.0 when using sorbents of similar composition. The proposed explanation considers the nature of functional groups existing on the surface of the sorbent to be a determining parameter. The negative Y-intercept of the kinetic plot is considered to be a result of relatively slow activation of adsorption centers by protonation. Based on these assumptions, the possibility of existence of active centers with high activation rate, strongly affected by pH, and active centers with low activation rate, less affected by pH, on titanium dioxide surface was postulated.