Sustainable pathway towards red mud valorization through biomass thermochemical conversion and metals recovery
Pedro Henrique Cabral de Souza, Klas Engvall, Frederico Marques Penha, Efthymios Kantarelis, Shareq Mohd Nazir
Abstract
Red mud is a hazardous waste of the alumina refining process, with 1–1.5 tons generated per ton of alumina produced. This study presents a first-of-its-kind understanding of a biomass-based pathway for recovering iron from red mud. Simultaneous red mud reduction and biomass gasification (SRG) is proposed as a viable pathway to produce zero-valent iron. This metallic iron can potentially be recovered by weak magnetic separation and integrated into the iron-making industry. The steps of the red mud-biomass phenomena were investigated through thermogravimetric analysis followed by XRD characterization. Complete reduction from Fe 3+ to Fe 0 was achieved at temperatures near 900 °C and verified by XRD, XPS, and FTIR. Bench-scale SGR experiments were also performed to survey the compositions of gaseous and tar products. Bench-scale SRG experiments confirmed increased syngas (CO and H 2 ) production and demonstrated the tar-cracking catalytic activity of red mud.