Production of Alumina from Secondary Aluminum Dross by Hydrometallurgical Process

Efficiently extracting alumina from secondary aluminum dross by the H2SO4 leaching method was proposed in the present work. SAD was washed and dried before the H2SO4 leaching. NH4HCO3 solution was used to adjust the appropriate pH value to precipitate aluminum from pregnant leaching solution. The products of leaching and precipitation were analyzed by x-ray diffraction (XRD) and scanning electron microscopy (SEM); 98.3% of the aluminum was extracted under the condition of leaching temperature of 90?, leaching time of 3 h, 30 wt.% H2SO4 solution, and ratio of liquid to solid (ml/g) of 10. The maximum precipitation rate of aluminum can reach 98.5% with a pH of 6.0, a precipitation time of 60 min, and a precipitation temperature of 50?. The overall recovery of aluminum in the leaching and precipitation stages was 96.83%. The leaching reaction between SAD and sulfuric acid was controlled by internal diffusion in the temperature range of 60?-90?. This process achieved the efficient extraction of aluminum from SAD and relieved the potential threat of SAD pollution; it can be extended to improve resource utilization for a broad range of solid waste containing aluminum.