1237
Technospheric Mining of Rare Earth Elements from Acid-Crack
Leach Tailings
K Yamini, Laurence Dyer
Western Australian School of Mines: Minerals, Energy, and Chemical Engineering, Faculty of Science and Engineering,
Curtin University, Kalgoorlie, Western Australia
ABSTRACT: The global transition towards low-carbon technologies has increased the demand for an expanded
supply of critical minerals such as rare earth elements. To avoid any bottleneck situation, it is advisable to
process these elements from secondary sources such as slag, tailings, discarded batteries, etc. Technospheric
mining is an umbrella term encompassing the extraction of valuable products from these anthropogenic waste
materials. The study applies this concept to extract rare earth elements (REE) from acid crack and leach (ACL)
residue, an industrial byproduct. A previously developed two-stage leaching process utilising oxalic acid and
ethylenediaminetetraacetic acid (EDTA) for monazite was employed to understand the reactivity of this feed.
Observations revealed that most of the reaction in oxalic acid occurred within the first hour. Unlike other feed
materials where the REE was reprecipitated as oxalates, the ACL residue left significant REE in the solution. The
relationship between oxalic acid concentration and feed reactivity was evaluated by altering the concentration
of oxalic acid. An additional dose of oxalic acid was added to study the feed response. A brief comparison of the
reaction between ACL residue and other feedstocks is presented for context.
Keywords: Technosphere, Oxalic Acid, EDTA, Rare Earth Elements
INTRODUCTION
Rare earth elements (REE) are 17 elements that include the
lanthanide series, scandium, and yttrium. These elements
possess unique physical properties like magnetic, electri-
cal, catalytic, and optical, making them employable in
diverse fields (Gupta &Krishnamurthy, 2005). However,
they have very similar chemical properties that make REE
extraction difficult. The majorly adopted industrial process-
ing routes involve beneficiation followed by either acid bak-
ing or caustic soda digestion (Davris et al., 2017 Gupta
&Krishnamurthy, 2005). These processes utilise strong
chemicals and emit harmful gases. Also, a high-grade con-
centrate is needed for the process to be economical. The
global transition towards clean and sustainable technolo-
gies is highly dependent on a consistent supply of REE. The
current global REE market, characterised by the monopoly
of the Chinese government and price volatility (Barakos et
al., 2022), necessitates the need to process these elements
from alternate sources (Yamini &Dyer, 2023).
Extraction from secondary resources like mine tail-
ings and discarded electronics mitigates the geopolitical
risks associated with the REE supply chain by reducing
the dependence on concentrated REE production regions.
The concept of extracting from waste materials is known
as technospheric mining (Lim &Alorro, 2021). The tech-
nosphere, an artificial component of the environment,
Technospheric Mining of Rare Earth Elements from Acid-Crack
Leach Tailings
K Yamini, Laurence Dyer
Western Australian School of Mines: Minerals, Energy, and Chemical Engineering, Faculty of Science and Engineering,
Curtin University, Kalgoorlie, Western Australia
ABSTRACT: The global transition towards low-carbon technologies has increased the demand for an expanded
supply of critical minerals such as rare earth elements. To avoid any bottleneck situation, it is advisable to
process these elements from secondary sources such as slag, tailings, discarded batteries, etc. Technospheric
mining is an umbrella term encompassing the extraction of valuable products from these anthropogenic waste
materials. The study applies this concept to extract rare earth elements (REE) from acid crack and leach (ACL)
residue, an industrial byproduct. A previously developed two-stage leaching process utilising oxalic acid and
ethylenediaminetetraacetic acid (EDTA) for monazite was employed to understand the reactivity of this feed.
Observations revealed that most of the reaction in oxalic acid occurred within the first hour. Unlike other feed
materials where the REE was reprecipitated as oxalates, the ACL residue left significant REE in the solution. The
relationship between oxalic acid concentration and feed reactivity was evaluated by altering the concentration
of oxalic acid. An additional dose of oxalic acid was added to study the feed response. A brief comparison of the
reaction between ACL residue and other feedstocks is presented for context.
Keywords: Technosphere, Oxalic Acid, EDTA, Rare Earth Elements
INTRODUCTION
Rare earth elements (REE) are 17 elements that include the
lanthanide series, scandium, and yttrium. These elements
possess unique physical properties like magnetic, electri-
cal, catalytic, and optical, making them employable in
diverse fields (Gupta &Krishnamurthy, 2005). However,
they have very similar chemical properties that make REE
extraction difficult. The majorly adopted industrial process-
ing routes involve beneficiation followed by either acid bak-
ing or caustic soda digestion (Davris et al., 2017 Gupta
&Krishnamurthy, 2005). These processes utilise strong
chemicals and emit harmful gases. Also, a high-grade con-
centrate is needed for the process to be economical. The
global transition towards clean and sustainable technolo-
gies is highly dependent on a consistent supply of REE. The
current global REE market, characterised by the monopoly
of the Chinese government and price volatility (Barakos et
al., 2022), necessitates the need to process these elements
from alternate sources (Yamini &Dyer, 2023).
Extraction from secondary resources like mine tail-
ings and discarded electronics mitigates the geopolitical
risks associated with the REE supply chain by reducing
the dependence on concentrated REE production regions.
The concept of extracting from waste materials is known
as technospheric mining (Lim &Alorro, 2021). The tech-
nosphere, an artificial component of the environment,