3387
Evaluating Environmentally Friendly Lixiviants for Lithium
Recovery from Montmorillonite Clays
Cara Haller, Christie Dorfling
Department of Chemical Engineering, Stellenbosch University
ABSTRACT: The exploration and development of low grade lithium-bearing deposits, such as clays, are gaining
increasing interest due to the exponential growth in lithium demand. Traditional hydrometallurgical processing
routes for lithium recovery use strong mineral acids, which pose environmental hazards. In this study, a range
of organic acids, with a potentially lower environmental impact compared to traditional processing routes,
were evaluated for lithium recovery from montmorillonite clays. Using a specific organic acid, 82% lithium
dissolution was achieved after 6 hours, with an acid concentration of 2 M, at 40°C and 8% solids.
INTRODUCTION
The global demand for lithium is increasing exponentially
due to its application in electric vehicles, grid energy storage
systems and portable electronic devices. Primary resources
of lithium can be grouped into three categories: (i) peg-
matitic rock, (ii) brine, and (iii) sedimentary deposits.
Up until recently, sedimentary lithium-bearing deposits,
such as clays, were not considered economically viable to
exploit, due to relatively low lithium grades. However, with
the exponential growth in lithium demand, there is a shift
towards the exploration and development of these lower
grade lithium resources (Grant and Goodenough 2021
Grant 2019 Li et al. 2019). Lithium-bearing clay depos-
its are of particular interest in Western North America,
with a number of projects currently under development
to extract lithium on a commercial scale (Noram Lithium
Corporation 2022 Grant 2019).
Exploration in Southern Africa has led to the identifica-
tion of lithium-bearing clay deposits that exhibit geochemi-
cal similarities to some of the deposits in Western North
America, with the predominant clay mineral identified
as montmorillonite. In contrast to lithium recovery from
pegmatitic rock and some refractory clay minerals, lithium
recovery from montmorillonite clay deposits typically does
not require roasting prior to leaching. Consequently, sev-
eral commercial developments in Western North America
are proposing direct leaching as the preferred route for lith-
ium recovery from clay deposits (Grant 2019).
Montmorillonite is a clay mineral of the smectite
group, belonging to the larger class of phyllosilicate miner-
als. A simplified two-dimensional diagram of the structure
of montmorillonite is presented in Figure 1. Phyllosilicate
minerals are composed of silica tetrahedral sheets, and
alumina or magnesium oxide octahedral sheets. 2:1 phyl-
losilicates, such as smectite, have one octahedral sheet sand-
wiched between two tetrahedral sheets. These three sheets
make up a single framework layer of the clay mineral.
Cations in the framework layers are often substituted by
other cations with a lower charge. For example, in smec-
tites, Si4+ in the tetrahedral sheet is often substituted by
Al3+, while in the octahedral sheet, substitution of Al3+ by
Mg2+ is common. As a result of these substitutions, nega-
tive charges are produced on these sheets. To compensate
for this charge imbalance, cations coordinate to the surfaces
of adjacent tetrahedral sheets between the 2:1 layers, also
known as the interlayer space. These cations are hydrated
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3387
Evaluating Environmentally Friendly Lixiviants for Lithium
Recovery from Montmorillonite Clays
Cara Haller, Christie Dorfling
Department of Chemical Engineering, Stellenbosch University
ABSTRACT: The exploration and development of low grade lithium-bearing deposits, such as clays, are gaining
increasing interest due to the exponential growth in lithium demand. Traditional hydrometallurgical processing
routes for lithium recovery use strong mineral acids, which pose environmental hazards. In this study, a range
of organic acids, with a potentially lower environmental impact compared to traditional processing routes,
were evaluated for lithium recovery from montmorillonite clays. Using a specific organic acid, 82% lithium
dissolution was achieved after 6 hours, with an acid concentration of 2 M, at 40°C and 8% solids.
INTRODUCTION
The global demand for lithium is increasing exponentially
due to its application in electric vehicles, grid energy storage
systems and portable electronic devices. Primary resources
of lithium can be grouped into three categories: (i) peg-
matitic rock, (ii) brine, and (iii) sedimentary deposits.
Up until recently, sedimentary lithium-bearing deposits,
such as clays, were not considered economically viable to
exploit, due to relatively low lithium grades. However, with
the exponential growth in lithium demand, there is a shift
towards the exploration and development of these lower
grade lithium resources (Grant and Goodenough 2021
Grant 2019 Li et al. 2019). Lithium-bearing clay depos-
its are of particular interest in Western North America,
with a number of projects currently under development
to extract lithium on a commercial scale (Noram Lithium
Corporation 2022 Grant 2019).
Exploration in Southern Africa has led to the identifica-
tion of lithium-bearing clay deposits that exhibit geochemi-
cal similarities to some of the deposits in Western North
America, with the predominant clay mineral identified
as montmorillonite. In contrast to lithium recovery from
pegmatitic rock and some refractory clay minerals, lithium
recovery from montmorillonite clay deposits typically does
not require roasting prior to leaching. Consequently, sev-
eral commercial developments in Western North America
are proposing direct leaching as the preferred route for lith-
ium recovery from clay deposits (Grant 2019).
Montmorillonite is a clay mineral of the smectite
group, belonging to the larger class of phyllosilicate miner-
als. A simplified two-dimensional diagram of the structure
of montmorillonite is presented in Figure 1. Phyllosilicate
minerals are composed of silica tetrahedral sheets, and
alumina or magnesium oxide octahedral sheets. 2:1 phyl-
losilicates, such as smectite, have one octahedral sheet sand-
wiched between two tetrahedral sheets. These three sheets
make up a single framework layer of the clay mineral.
Cations in the framework layers are often substituted by
other cations with a lower charge. For example, in smec-
tites, Si4+ in the tetrahedral sheet is often substituted by
Al3+, while in the octahedral sheet, substitution of Al3+ by
Mg2+ is common. As a result of these substitutions, nega-
tive charges are produced on these sheets. To compensate
for this charge imbalance, cations coordinate to the surfaces
of adjacent tetrahedral sheets between the 2:1 layers, also
known as the interlayer space. These cations are hydrated

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