Investigation of leaching kinetics of aluminum extraction from secondary aluminum dross with use of hydrochloric acid

Hydrochloric acid leaching is a good way to extract aluminum from secondary aluminum dross (SAD). However, the leaching kinetics of this process is still unclear. This study investigated the leaching kinetics of aluminum extraction from SAD by using hydrochloric acid. Leaching test results showed that the leaching rate of aluminum in SAD could reach 22% under optimal conditions. According to the analyses of X-ray fluorescence, X-ray diffraction, and scanning electron microscopy with energy-dispersive spectrometer, the components that dissolve in hydrochloric acid include metal aluminum, aluminum nitride and aluminum oxide in SAD. Kinetic studies revealed that the dissolutions of metal aluminum and aluminum oxide conformed to the 1-D diffusion-controlled model and the Avrami model, respectively. The dissolution of aluminum nitride was mainly controlled by surface chemical reaction in the contracting volume model. The activation energies of metal aluminum, aluminum oxide, and aluminum nitride in the leaching process were 6.92, 11.16, and 40.93 kJ.mol(-1), respectively. The activation energy of aluminum nitride was the highest, indicating that it was the most difficult to dissolve. For process practicality, the effective decomposition of aluminum nitride could realize the maximum recovery of aluminum in SAD.