Leaching Process Investigation of Secondary Aluminum Dross: The Effect of CO2 on Leaching Process of Salt Cake from Aluminum Remelting Process

• Published in: Metallurgical and materials transactions. B, Process metallurgy and materials processing science Vol. 43; no. 5; pp. 1220 - 1230
• Main Authors: Li, Peng, Guo, Min, Zhang, Mei, Teng, Lidong, Seetharaman, Seshadri
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01-10-2012; Springer; Springer Nature B.V
• Subjects: Aluminum; Applied sciences; Carbon dioxide; Characterization and Evaluation of Materials; Chemical reactions; Chemistry and Materials Science; Exact sciences and technology; Extraction processes; Materials Science; Melting; Metallic Materials; Metallurgy; Metals. Metallurgy; Nanotechnology; Production of metals; Structural Materials; Surfaces and Interfaces; Thin Films; Leach Residue; Carbonate Water; Metallic Aluminum; Secondary Aluminum; Boric Acid Solution; Lixiviation; Carbon dioxide; Hydrometallurgy
• ISSN: 1073-5615; 1543-1916
• DOI: 10.1007/s11663-012-9678-7

For the recycling/disposal of aluminum dross/salt cake from aluminum remelting, aqueous leaching offers an interesting economic process route. One major obstacle is the reaction between the AlN present in the dross and the aqueous phase, which can lead to the emission of NH
3
gas, posing a serious environmental problem. In the current work, a leaching process using CO
2
-saturated water is attempted with a view to absorb the ammonia formed
in situ
. The current results show that at a solid-to-liquid ratio of 1:20 and 3 hours at 291 K (18 °C), the extraction of Na and K from the dross could be kept as high as 95.6 pct and 95.9 pct respectively. At the same time, with continuous CO
2
bubbling, the mass of escaping NH
3
gas decreased from 0.25 mg in pure water down to <0.006 mg, indicating effective absorption of ammonia by carbonized water. Furthermore, the results in the case of the leaching experiments with synthetic AlN show that the introduction of CO
2
causes hindrance to the hydrolysis of AlN. The plausible mechanisms for the observed phenomena are discussed. The concept of the leaching of the salt cake by carbonated water and the consequent retention of AlN in the leach residue opens up a promising route toward an environment-friendly recycling process for the salt cake
viz.
recovery of the salts, utilization of CO
2
, and further processing of the dross residue, toward the synthesis of AlON from the leach residues.