Co-Treatment of Spent Pot-Lining and Red Mud for Carbon Reutilization and Recovery of Iron, Aluminum and Sodium by Reductive Roasting Process

Spent pot-lining (SPL) and red mud (RM) are the two major solid wastes of the aluminum industry. In this study, an innovative method has been proposed for co-treatment of SPL and RM to reuse carbon and recover metal (iron, aluminum and sodium) by a reductive roasting-leaching-magnetic separation process (RRLMS process). Moreover, the transformation behaviors of fluoride, cyanide and sulfur present in these residues were studied. The effects of parameters such as temperature, CaO/SiO2 molar ratio, addition amount of SPL, Na2O/Al2O3 molar ratio and roasting time on the result of the process were investigated. Under optimum conditions, the recovery extents of Al2O3 and Na2O were 83.12 and 91.80 pct, respectively. The corresponding leaching extent and loss of F upon roasting process were 16.03 and 35.27 pct, respectively, and only 29.02 pct of ST in the roasted product was leached. Furthermore, reduction extent of 78.65 pct and a metallization extent of 62.83 pct for iron minerals were achieved. The SPL-RM mixture after treatment was rendered non-hazardous. Finally, wet magnetic separation at 1.2 A current (magnetic field strength of approximately 130 mT) provided 30.83 wt pct concentrate yield with 59.09 wt pct total iron concentration and iron recovery extent of 65.25 pct from the leached residue.