Extraction of Aluminum Based on NH4HSO4 Roasting and Water Leaching from Secondary Aluminum Dross

A NH4HSO4 roasting and water leaching process has been proposed to efficiently extract aluminum from secondary aluminum dross (SAD). The aluminum was recovered in the form of Al(OH)3 after precipitation by adjusting the PH of the leaching liquid. Al2O3 was prepared by roasting the Al(OH)3. The effects of the extracting behaviors of aluminum under different processing conditions were systematically studied. SEM, XRD, FT-IR, and TG/DTA have been used to elucidate the phase evolution during the whole process. After the NH4HSO4 roasting and water leaching, 94.9% of the aluminum was extracted with a m(NH4HSO4)/m(Al) mass ratio of 7, roasted at 400°C, and maintained for 90 min. Optimal leaching conditions were a leaching temperature of 90°C, a ratio of liquid to solid (L/S:g/g) of 10 and a leaching time of 80 min. During roasting, the NH4HSO4 reacted with the aluminum and formed NH4Al(SO4)2 dissolved in water, and 98.4% of the aluminum was precipitated from the leaching liquid by adjusting the pH value of 6.0, a precipitation time of 120 min, and a precipitation temperature of 60°C. The purity of the Al2O3 was 98. 8% by roasting Al(OH)3 at 1200°C.