Leaching kinetics of uranium, rare earth elements and copper using tartaric acid from El Allouga ore material, Southwestern Sinai, Egypt

The leaching process of uranium (U), rare earth elements (REEs) and copper (Cu) from El Allouga ore using tartaric acid was examined. The leaching condition time of reaction, temperature, tartaric acid concentration, contact time, particle size, solid–liquid ratio and stirring speed were studied. The results obtained revealed that the dissolution rate was strongly influenced by the increase in the acid concentration, the solid/liquid ratio, the contact time, the temperature, and the stirring speed on the leaching efficiency. The analysis of the experimental kinetic data was well interpreted with a shrinking-core model, which showed that the dissolution mechanism follows diffusion reaction as a rate determining step with apparent activation energy equals to 20.09, 23.85 and 23.12 kJ/ mol for U, REEs and Cu, respectively. The low value of the activation energy confirmed the results that the rate of leaching is controlled by the diffusion of reactants and leaching products through a porous ore. The dissolution efficiency of uranium was about 94.5%, while the REEs and copper dissolution efficiency was about 92.6% and 97.5%, respectively. According to this model and the experimental results, the dissolution rate can be expressed by the following semi-empirical equation; 1–3 (1-X) 2/3 + 2 (1-X) = k1t