Dissolution Kinetics of Carbonates in Low-Grade Microgranular Phosphate Ore Using Organic Acids as Leaching Agents

The present study investigates the process of selective leaching of low-grade phosphate ore of the Karatau basin using organic acids such as formic and citric acids. Chemical and instrumental analyses of the investigated phosphate ore were carried out, including X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), and Fourier-transform infrared spectroscopy (FTIR). Based on experimental data, reaction rate constants were calculated, and the obtained activation energies for each of the reagents were used. The reaction rate constants indicate that formic acid led to a more gradual increase in P2O5 concentration over time, while citric acid demonstrates a more significant increase in phosphorus concentration at all temperatures, especially at 70 °C. The activation energy for formic acid is 14.69 kJ/mol, indicating a diffusion-controlled reaction mechanism, whereas the activation energy for citric acid is higher, i.e., 35.78 kJ/mol, suggesting a more complex mechanism involving both diffusion and chemical processes. The present study highlights the importance of selecting appropriate reaction conditions to achieve maximum efficiency for the leaching of phosphate ore, depending on both temperature and reagent used.