1695
Comparative Process Analysis for Extraction of Metallic Values
from Indian Red Mud
Nikhil Dhawan, Shrey Agrawal
Materials Recycling Laboratory, Department of Metallurgical and Materials Engineering,
Indian Institute of Technology, Roorkee, India
ABSTRACT: Red mud is an inevitable by-product of the aluminum industry, which needs to be tackled due to
environmental concerns and process sustainability. Red mud is explored as a potential source of iron, aluminum,
titanium, scandium, and rare earth elements. Comparative analysis of the pyro and hydrometallurgical processes
developed by authors is carried out based on preliminary cost and energy analysis to assess the feasibility. The
alkali baking (AB-AL) process yields 84% recovery of metals from red mud meanwhile, the acid baking (AB-WL)
process is the most economical, consuming ~1 MJ/kg of electrical energy. The novel baking technology is more
efficient than the leaching and reduction processes for complex structured red mud processing. Alternatively,
the recovery of titanium and REEs generates a major value (75%) meanwhile, iron and aluminum constituting
70 wt.% of red mud, contribute only 20–25% to the value generated from red mud. The study helps define the
potential value of the differently sourced red mud and map the most suitable processing technique for metal
recovery.
Keywords: Red mud, leaching, baking, reduction, energy, cost analysis
INTRODUCTION
Red mud is generated in the Bayer’s process from the baux-
ite ore. The physicochemical characteristics of red mud are
the functionality of ore composition and processing param-
eters. Approximately 1–2.5 tons of red mud is generated
to produce 1 ton of smelter-grade aluminum hydroxide
(Agrawal et al., 2019 Rai et al., 2020). Consequently, red
mud generation is increasing, with a global accumulation
of ~150 million tons per annum in 2017, and the total
stockpile worldwide is estimated at 4 billion tons (Agrawal
and Dhawan, 2021b). The pH value of red mud is 10–12
due to the presence of sodium values, and high alkalinity
makes it corrosive.
The limited applications of red mud have led to neg-
ligible consumption of red mud, and the majority frac-
tion is stockpiled in landfills. The red mud stockpile is an
industrial liability nevertheless, landfilling is preferred due
to associated economic and social benefits. The red mud
treatment is estimated to cost around 5–9 US$ per ton of
red mud, equivalent to 2% of the alumina value (Ujaczki et
al., 2018). Despite the associated challenges with red mud
management, it is regarded as a potential resource rather
than a waste product. The literature review on red mud
shows that the metal extraction efficiency varies widely with
different red mud samples, and suitable process routes may
differ depending upon the red mud composition. The red
mud composition is the governing factor for the selective
Comparative Process Analysis for Extraction of Metallic Values
from Indian Red Mud
Nikhil Dhawan, Shrey Agrawal
Materials Recycling Laboratory, Department of Metallurgical and Materials Engineering,
Indian Institute of Technology, Roorkee, India
ABSTRACT: Red mud is an inevitable by-product of the aluminum industry, which needs to be tackled due to
environmental concerns and process sustainability. Red mud is explored as a potential source of iron, aluminum,
titanium, scandium, and rare earth elements. Comparative analysis of the pyro and hydrometallurgical processes
developed by authors is carried out based on preliminary cost and energy analysis to assess the feasibility. The
alkali baking (AB-AL) process yields 84% recovery of metals from red mud meanwhile, the acid baking (AB-WL)
process is the most economical, consuming ~1 MJ/kg of electrical energy. The novel baking technology is more
efficient than the leaching and reduction processes for complex structured red mud processing. Alternatively,
the recovery of titanium and REEs generates a major value (75%) meanwhile, iron and aluminum constituting
70 wt.% of red mud, contribute only 20–25% to the value generated from red mud. The study helps define the
potential value of the differently sourced red mud and map the most suitable processing technique for metal
recovery.
Keywords: Red mud, leaching, baking, reduction, energy, cost analysis
INTRODUCTION
Red mud is generated in the Bayer’s process from the baux-
ite ore. The physicochemical characteristics of red mud are
the functionality of ore composition and processing param-
eters. Approximately 1–2.5 tons of red mud is generated
to produce 1 ton of smelter-grade aluminum hydroxide
(Agrawal et al., 2019 Rai et al., 2020). Consequently, red
mud generation is increasing, with a global accumulation
of ~150 million tons per annum in 2017, and the total
stockpile worldwide is estimated at 4 billion tons (Agrawal
and Dhawan, 2021b). The pH value of red mud is 10–12
due to the presence of sodium values, and high alkalinity
makes it corrosive.
The limited applications of red mud have led to neg-
ligible consumption of red mud, and the majority frac-
tion is stockpiled in landfills. The red mud stockpile is an
industrial liability nevertheless, landfilling is preferred due
to associated economic and social benefits. The red mud
treatment is estimated to cost around 5–9 US$ per ton of
red mud, equivalent to 2% of the alumina value (Ujaczki et
al., 2018). Despite the associated challenges with red mud
management, it is regarded as a potential resource rather
than a waste product. The literature review on red mud
shows that the metal extraction efficiency varies widely with
different red mud samples, and suitable process routes may
differ depending upon the red mud composition. The red
mud composition is the governing factor for the selective