Extraction of Alumina and Alumina-Based Cermets from Iron-Lean Red Muds Using Carbothermic Reduction of Silica and Iron Oxides

Rita Khanna (), Dmitry Zinoveev, Yuri Konyukhov, Kejiang Li, Nikita Maslennikov, Igor Burmistrov, Jumat Kargin, Maksim Kravchenko and Partha Sarathy Mukherjee
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Rita Khanna: School of Materials Science and Engineering (Ret.), The University of New South Wales, Sydney, NSW 2052, Australia
Dmitry Zinoveev: Department of Mineral Processing and Industrial Wastes Recycling, National University of Science and Technology “MISIS”, Moscow 119049, Russia
Yuri Konyukhov: Department of Mineral Processing and Industrial Wastes Recycling, National University of Science and Technology “MISIS”, Moscow 119049, Russia
Kejiang Li: School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
Nikita Maslennikov: Department of Mineral Processing and Industrial Wastes Recycling, National University of Science and Technology “MISIS”, Moscow 119049, Russia
Igor Burmistrov: Engineering Centre, Plekhanov Russian University of Economics, Moscow 117997, Russia
Jumat Kargin: Technical Physics Department, L.N. Gumilyov Eurasian National University, Astana 010008, Kazakhstan
Maksim Kravchenko: Moscow Power Engineering Institute, National Research University, Moscow 111250, Russia
Partha Sarathy Mukherjee: Independent Researcher, Bhubaneshwar 751013, Orissa, India

Sustainability, 2025, vol. 17, issue 15, 1-18

Abstract: A novel strategy has been developed for extracting value-added resources from iron-lean, high-alumina- and -silica-containing red muds (RMs). With little or no recycling, such RMs are generally destined for waste dumps. Detailed results are presented on the carbothermic reduction of 100% RM (29.3 wt.% Fe 2 O 3 , 22.2 wt.% Al 2 O 3 , 20.0 wt.% SiO 2 , 1.2 wt.% CaO, 12.2 wt.% Na 2 O) and its 2:1 blends with Fe 2 O 3 and red mill scale (MS). Synthetic graphite was used as the reductant. Carbothermic reduction of RM and blends was carried out in a Tamman resistance furnace at 1650 °C for 20 min in an Ar atmosphere. Reduction residues were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), elemental mapping and X-ray diffraction (XRD). Small amounts of Fe 3 Si alloys, alumina, SiC and other oxide-based residuals were detected in the carbothermic residue of 100% RM. A number of large metallic droplets of Fe–Si alloys were observed for RM/Fe 2 O 3 blends; no aluminium was detected in these metallic droplets. A clear segregation of alumina was observed as a separate phase. For the RM/red MS blends, a number of metallic Fe–Si droplets were seen embedded in an alumina matrix in the form of a cermet. This study has shown the regeneration of alumina and the formation of alumina-based cermets, Fe–Si alloys and SiC during carbothermic reduction of RM and its blends. This innovative recycling strategy could be used for extracting value-added resources from iron-lean RMs, thereby enhancing process productivity, cost-effectiveness of alumina regeneration, waste utilization and sustainable developments in the field.

Keywords: red mud; industrial waste; alumina regeneration; recycling; cermets; ferro-silicon alloys (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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