Leaching kinetics of magnesium from spent magnesia-chromium refractories

In this study, the microscopic properties of spent magnesia-chromium refractories before and after leaching were detected by SEM-EDS and BSE. In addition, the influence of conditions on magnesium leaching was studied by leaching kinetics test, and the kinetics of the leaching process was analyzed by statistical and graphical methods. The results indicate that the relationship between different phases in raw material is complicated that the leaching residue is chromite spinel, and the particles have various holes and cracks. Increasing temperature, hydrochloric acid concentration and liquid-solid ratio can accelerate leaching velocity of magnesium, thereby promoting the whole leaching process, and the promotion effect of temperature is the most significant. The process of leaching magnesium from spent magnesia-chromium refractories conforms to the progressive-conversion model with chemical reaction being the rate-controlling step, in which the corresponding apparent activation energy was 69.11 kJ/mol, and its kinetic equation can be expressed as follows: X /(1− X )=4.898×10 8 ×C HCL 0.7982 ×(L/S) 0.7407 ×e −8312/ T × t 0.9276 .