Synergistic reutilization of red mud and spent pot lining for recovering valuable components and stabilizing harmful element

Abstract A large amounts of red mud (RM) and spent pot lining (SPL) produced during aluminum extraction and electrolysis are restricting the sustainable development of aluminum industry. In this study, an integrated route for synergistic reutilization of RM and SPL was proposed to deal with this dilemma. To improve the recovery efficiency of metallic Fe, Si and Al were firstly extracted from RM to synthesize 4A-zeolite. Afterwards, reductive roasting process was employed for iron recovery using SPL as reducing agent. Metallic Fe obtained from the reductive roasting were collected by wet magnetic separation to yield valuable iron concentrate from nonmagnetic residues. Thermodynamic studies using Factsage 7.1 software were implemented to determine the transformation of mineral phases, and orthogonal design experiments containing various parameters like SPL blend ratio, temperature, and retention time were investigated to optimize the conditions. The reductive process performed at blend ratio of 7 wt%, temperatures of 900 °C and 240 min retention time under N2 atmosphere induced higher conversion yield of metallic Fe (88.84 wt%). Soluble fluorides in SPL resulted in its hazardous properties, but the formation of cuspidine (Ca4Si2F2O7) in nonmagnetic residues suggested that the route not only reutilized valuable components, but also stabilized the hazardous element.