Next Article in Journal
Influence of Mineralogical and Petrographic Properties on the Mechanical Behavior of Granitic and Mafic Rocks
Previous Article in Journal
Mineral Chemistry and Whole-Rock Analysis of Magnesian and Ferroan Granitic Suites of Magal Gebreel, South Eastern Desert: Clues for Neoproterozoic Syn- and Post-Collisional Felsic Magmatism
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Minerals
Volume 15
Issue 7
10.3390/min15070750
minerals-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Review

Froth Flotation of Lepidolite—A Review

by
Xusheng Yang
1,2,
Bo Feng
1,2,* and
Longxia Jiang
2
1
Yichun Lithium New Energy Industry Research Institute, Jiangxi University of Science and Technology, Yichun 336000, China
2
Jiangxi Province Key Laboratory of Mining and Metallurgy Environmental Pollution Control, Jiangxi University of Science and Technology, Ganzhou 341000, China
*
Author to whom correspondence should be addressed.
Minerals 2025, 15(7), 750; https://doi.org/10.3390/min15070750
Submission received: 12 June 2025 / Revised: 5 July 2025 / Accepted: 16 July 2025 / Published: 17 July 2025
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
Browse Figures
Versions Notes

Abstract

As one of the important lithium resource sources, lepidolite has become a new energy strategic resource research hot spot. The efficient flotation of lepidolite directly affects the recovery and economic value of lithium resources. This paper systematically reviews the flotation research progress of lepidolite, focusing on the influence of the type of capture agent and process parameters (pH, activator, and depressant) on flotation. In view of the separation problems caused by the similarity of the surface properties of lepidolite and its associated gangue minerals (albite, feldspar, and quartz), the strategies for regulating the crystal structure of the minerals and their surface properties are analyzed. In addition, the lepidolite flotation process and its challenges are summarized, including poor selectivity of chemicals, fine mineral embedded size, easy to form sludge, and insufficient environmental friendliness, etc. The future development direction of lepidolite flotation technology is also prospected, which provides theoretical support and reference for the efficient recovery of lepidolite.

1. Introduction

As a strategic resource for the green energy transition in the 21st century, lithium plays an irreplaceable role in high-tech fields such as lithium-ion batteries, new energy vehicles, energy storage systems, and aeronautics and astronautics [1,2,3,4,5]. Its economic value is closely related to its unique properties. Being the lightest alkali metal with a density of merely 0.534 g/cm3 [6]. Lithium also boasts a high electrode potential and rapid redox kinetics, enabling efficient electron transfer in electrochemical reactions and making it a highly electrochemical element [7,8,9]. These properties endow lithium with excellent energy storage capabilities. In addition to energy storage, lithium has diverse applications, including lubricants, catalysts, and ceramics [10,11,12]. In 2018, the global lithium consumption market was dominated by the battery and energy storage industries (37%), driven by the new energy revolution. The traditional ceramic manufacturing sector held a significant position with a 30% share, while applications in lubricants (8%) and metal smelting (6%) accounted for relatively smaller proportions [13]. Regarding production, in 2016, lithium resources were mainly concentrated in Australia, Chile, and Argentina. Australia led global production with 14,300 tons of lepidolite, accounting for 40.5% of the global total, followed by Chile and Argentina in second and third places [14]. The global lithium resource distribution in 2022 is illustrated in Figure 1 [15].
Before the 21st century, most lithium came from mineral resources [16]. Due to its low economic cost, brine became the main source of lithium resources, causing many lithium mining companies to close down [16,17]. However, globally, lithium-rich brine with economic benefits is extremely unevenly distributed, mainly concentrated in Argentina, Bolivia, and Chile, which are known as the “Lithium Triangle” [18,19]. Currently, brine and hard rock ores are the primary sources of lithium, with over 65% of lithium production coming from brine and about 32% from hard rock ores [7,20,21,22]. Table 1 summarizes the production and reserves of lithium in global brine and hard rock ores. Chile and Argentina have the largest lithium reserves in brine. Australia, China, and Zimbabwe are the main producers of lithium from hard rock ores [23].
More than 100 kinds of hard rock ores contain lithium, but most have very low lithium content [7,8,24]. Researchers have found that in hard rock ores, lithium resources mainly exist in minerals such as lepidolite, spodumene, and triplite [9,25,26,27]. Currently, lithium brine is in harsh natural conditions, with difficult transport and high overall costs [28]. Therefore, lithium-bearing ores have become one of the main sources of lithium [29,30]. Lepidolite, a common lithium-bearing mineral with the chemical formula K(Li,Al)3(Al,Si)4O10(F,OH)2 [31,32], is a layered silicate mineral. It has large reserves and low mining costs, making it one of the most promising resources [30,33]. The process of lepidolite development is continuously improved. It is believed that the Li2O content in lepidolite concentrate collected by flotation is about 3%–5% [34,35,36,37]. The North American pegmatite belt is the largest lithium pegmatite in the world, with an average grade of 0.6% Li2O [37]. In the flotation process, the choice of collector is crucial [38]. Amine collectors and combinations of cationic and anionic collectors have become the main directions for lepidolite flotation. However, lepidolite often coexists with other silicate gangue minerals [39]. They have extremely similar surface properties and structures, and are somewhat floatable. Thus, separating lepidolite from gangue in flotation is a major challenge [40]. This review aims to summarize and discuss the mineral crystallography and properties of lepidolite, summarize its flotation processes, and highlight the latest findings in froth flotation to provide a reference for efficient lepidolite separation.

2. Crystal Structure and Properties of Lepidolite and Major Gangue Minerals

2.1. Crystal Structure and Properties of Lepidolite

Lepidolite, a lithium-rich mica, has a complex monoclinic crystal structure [27,41]. Its frame consists of a T-O-T trilayer structure formed by two layers of [SiO4] tetrahedra and one layer of [AlO6] octahedra [42,43], as shown in Figure 2. This layered structure gives lepidolite excellent cleavage, allowing it to be peeled into flexible sheets along the layered planes [44]. This layered structure gives lepidolite excellent cleavage, allowing it to be peeled into flexible sheets along the layered planes [45,46]. Researchers often compare lepidolite with muscovite due to their structural similarities and good cleavage on the (0 0 1) plane [47,48,49]. In contrast, lepidolite has a typical triplet structure, where all three sites (M1, M2, and M3) in the octahedral layer are filled with cations [50]. Specifically, in the lepidolite crystal structure of lepidolite, there is a large octahedral site M1 occupied primarily by Li+ and two smaller octahedral sites M2 occupied by Al3+ [51]. This differential octahedral site occupancy reflects the heterovalent substitution of Li-Al in lepidolite. The charge balance of its layered structure is achieved by compensating for interlayer K ions, which is a key crystallochemical distinction of lepidolite from other mica minerals [52,53].
In addition, liberation analysis of lepidolite is a prerequisite for successful flotation separation, and its mineralogical characterization directly determines the recovery efficiency of lithium resources. As a typical layered silicate, lepidolite is often embedded in pegmatite in the form of fine-scale aggregates, which closely coexist with minerals such as quartz, albite, and muscovite. This complex state of existence makes it difficult to achieve complete liberation under rough grinding conditions. Only about 60% of the minerals can be completely separated from the gangue minerals to become a single particle; the rest of the gangue minerals and gangue minerals to form a difficult to select [37]. Such hyphenated particles cannot effectively adsorb the traps due to their mixed surface properties in flotation, and are eventually lost in the form of tailings, resulting in a loss of lithium recovery of more than 10%. Through mineral dissociation analysis, lepidolite release was positively correlated with grinding fineness. When the grinding fineness is increased to P80 = 50 μm, the degree of liberation can reach 90% [54]. However, excessive fine grinding will produce microfine particles, which are easy to cover the surface of lepidolite and enter the concentrate layer with the foam, affecting the concentration grade in this way [55]. Therefore, for the storage characteristics of lithium mica, it is necessary to customize the differentiated grinding and flotation scheme, and adopt “stage grinding—branch flotation” for the coarse-grained embedded flaky lithium mica, so as to achieve the synergistic optimization of the liberation efficiency and beneficiation cost.
Zeta potential is a key parameter for characterizing the surface properties of minerals and reflecting the distribution of surface charges [56]. Many studies have deeply explored the electrical properties of lepidolite. Research shows that lepidolite surfaces carry negative charges over a wide pH range (Figure 3) [57]. However, the surface charge of lepidolite reaches its isoelectric point (IEP) at a pH of about 2. Some researchers even believe that lepidolite has no IEP and that the IEP data for lepidolite are derived from literature [34,58]. The relationship between lepidolite surface charge and pH provides a theoretical basis for its applications in flotation, adsorption, and other surface chemical behaviors.

2.2. Crystal Structure and Properties of Major Gangue Minerals

Lepidolite deposits are unevenly distributed globally, but their mineral composition is relatively uniform. They mainly consist of the gangue minerals muscovite, quartz, and feldspar (including albite and microcline).

2.2.1. Crystal Structure and Properties of Muscovite

Muscovite, generally more common than lepidolite, has the chemical formula K2Al4(Si6Al2)O20(OH)4 [47]. It is a typical dioctahedral layered silicate mineral. It is colorless or silver-white. The tetrahedral layer is mainly composed of silicon atoms, but some are replaced by aluminum atoms. The octahedral layer is fully occupied by aluminum atoms, yet only two-thirds of the sites are filled, forming a unique dioctahedral arrangement [48]. In addition, muscovite has perfect cleavage on the (0 0 1) plane.
Muscovite exhibits various polymorphs (see Table 2 for polymorphic characteristics), whose formation is controlled by specific geodynamic conditions. Research shows that the 1M polymorph (e.g., hydrothermal muscovite) is usually stable in low-temperature environments. As the temperature rises, muscovite undergoes a polymorphic transformation sequence of 1M → 2M1. This phase change reflects the transition from a hydrothermal system to a medium to high temperature metamorphic environment.
The difference in lattice dimensions between M1 and M2 sites is significantly influenced by cation substitution in octahedral sites. Referring to the paradigm of lithium-containing muscovite studied by researchers [60], the lithium-containing terminal elements in the 2M1 polymorph show a typical coordination substitution mechanism: Li+ with Fe2+ displacing Al3+. Such cation exchange effects (Li+/Fe2+ → Al3+) can induce local lattice distortions in the intermediate coordination layer, which in turn affect the overall structural stability of the mica crystal. It should be emphasized that the above-mentioned substitution process may regulate the surface-interface reactivity of minerals by altering the distribution of surface hydroxyl groups and layer charge density. The change process is shown in Figure 4.

2.2.2. Crystal Structure and Properties of Feldspar

Feldspar, with the chemical formula (Na,K)(Al,Si)4O8, is the most abundant framework silicate mineral in the Earth’s crust (>60%) [61,62]. It has a monoclinic or triclinic crystal system (orthoclase: monoclinic/triclinic; plagioclase: triclinic). Feldspar is typically white or greyish-white, with a glassy luster, a Mohs hardness of about 6, and a density of 2.6–2.75 g/cm3. Its crystal structure consists of a 3D framework formed by Si-O and Al-O tetrahedra connected via shared oxygen atoms, with some Si atoms replaced by Al atoms [63,64,65]. In albite, lattice parameters are a = 8.144 Å, b = 12.789 Å, c = 7.160 Å, α = 94.13°, β = 116.59°, γ = 87.67°, and Al3+ orderly occupies T10 tetrahedral sites (occupancy > 95%), causing a 0.02 Å periodic displacement along the c-axis [66]. For orthoclase (KAlSi3O8), unit cell parameters are a = 8.56 Å, b = 12.96 Å, c = 7.19 Å, β = 116°, with Al3+ preferentially occupying T10 tetrahedral sites, and the Si-Al order directly affecting thermal stability [67].

2.2.3. Crystal Structure and Properties of Quartz

Quartz (SiO2), a stable framework silicate mineral formed by silicon-oxygen tetrahedra linked via covalent bonds, contains minor Fe2O3, Al2O3, and other oxides. Under standard conditions, it exhibits the α-quartz configuration (low-temperature form) and belongs to the trigonal crystal system [68,69,70]. Its color varies but is mainly colorless and transparent (rock crystal) or milky white, with a Mohs hardness of 7 and a density of approximately 2.6 g/cm3 [71,72]. Quartz has unit cell parameters of a = 4.913 Å and c = 5.405 Å, with three chemical formula units per cell [68]. Its crystal structure consists of [SiO4] tetrahedra connected by shared vertices, forming a three-dimensional spiral chain. This results in an asymmetric stretching vibration peak at 480 cm−1 in the Raman spectrum. At high temperatures (>573 °C), it undergoes a reconstructive phase transition (α → β-quartz) to the hexagonal crystal system [73]. Table 3 summarizes the basic characteristics of lepidolite and its main gangue minerals.

3. Lepidolite Flotation Process

3.1. Changes in Lepidolite Flotation Systems

Lepidolite flotation has evolved from acidic to more environmentally friendly processes. Early research exploited differences in the electrochemical properties of mineral surfaces, using cationic collectors in acidic media (pH~2) to separate lepidolite from silicate gangue. For example, the Bhappu & Fuerstenau [74] research team successfully recovered lepidolite from gangue under pH = 2 conditions, achieving good results. Under the condition that the dosage of tallow amine group is 3 · 2 10−5 M, the recovery of almost all lithium resources is realized, and the grade of Li2O is about 1.4%. However, this process had significant drawbacks, such as rapid equipment corrosion from the strong acid medium, poor foam layer stability, and a pronounced fine slime coating effect. To address these issues, a neutral flotation system was developed. Yang et al. [75] used a collector combination of dodecylamine (DDA) and sodium dodecylbenzene sulfonate (SDBS) at pH 7, achieving a Li2O grade of 2.3% and a recovery rate of 63%. Subsequently, Liu et al. [76] developed an HQ-330/DDA reagent combination at the same pH. This approach, using directed adsorption of reagent molecules to increase the contact angle difference between lepidolite and feldspar minerals, yielded the best flotation results for lepidolite at a dosage of 100 mg/L.

3.2. Innovations in New Flotation Technology for Lepidolite

Driven by the rising demand for lithium in new energy vehicles and batteries, researchers are developing new technologies for lepidolite flotation. For example, Zhang et al. [77] employed micronano bubbles (MNBs) to enhance the recovery of fine-grained lepidolite. With dodecylamine (DDA) and sodium oleate (NaOL), the recovery rate of such lepidolite increased from 31.5% to 45.8%. The Chen team [78] pioneered a flotation process of lepidolite without pre-refining. By leveraging the synergy between collectors and high molecular weight flocculants, they achieved selective flocculation flotation of high clay content lepidolite ore. The flocculant bridging effect in pulp enhanced the adhesion between target minerals and bubbles, effectively separating clay minerals from lepidolite and overcoming the high clay content bottleneck in conventional flotation. Ai et al. [79] developed tailings lepidolite recovery technology combining steam thermal activation with diluted pulp flotation. It uses steam thermal energy to activate mineral-surface lattice sites, prompting directional collector adsorption layers in the diluted pulp. This optimizes the flotation environment, boosting lithium-oxide recovery to 76.99% and providing a new solution for the efficient use of highly argillaceous tailings resources.

3.3. Industrialization Challenges and Synergistic Sorting Strategies

These innovative processes work well to enrich lepidolite in laboratories, but industrial use faces major challenges. Lepidolite deposits often have multiple metals and fine mineral grains. This makes separation difficult for single flotation methods. Such methods struggle with varying mineral surface features and interface reaction kinetics. Current research builds an integrated process system. It combines gravity-magnetic-electric separation for coarse mineral pre-concentration and uses flotation reagents to fine-tune surface features of micron-sized particles. This not only makes up for the technical limitations of single separation but also enhances lepidolite recovery through process optimization, providing a technical reference for complex deposit industrialization. For example, Filippov et al. [37] used optical ore sorting technology to separate coarse-grained lepidolite pegmatite and estimate the grade of lepidolite ore of different sizes. Then, they applied electrostatic separation to the lepidolite-rich fraction (>210 μm) and conducted flotation on the finer fraction (−210 + 63 μm) at a pH between 3 and 5. The final lepidolite concentrate had a Li2O grade of 4.2%–4.5% and a recovery rate of 87%–95%. Peng et al. [80] have developed an integrated “multi-stage grinding, magnetic separation synergy and sequential separation” process for the lepidolite deposit in Hunan, China. This process employed stepwise grinding for release, combined with weak magnetic pre-deironing and precise hydraulic cyclone grading to create different separation paths for coarse and fine particles. Coarse-grained minerals were pre-enriched by a high magnetic separation gradient, while fine-grained minerals used a combined cationic and anionic collector flotation system. By integrating magnetic-heavy-flotation technologies, they effectively separate lepidolite from coexisting silicate minerals. The final lepidolite concentrate had a Li2O grade of 2.57% and a recovery rate of 82.93%, setting an innovative example for efficiently developing granite-type lithium resources. In addition, the flow chart for effectively processing difficult lepidolite ore samples is shown in Figure 5.
The lepidolite flotation process is shifting from acidic to neutral systems, but this shift brings challenges such as slime interference and fine particle loss. Table 4 lists common lepidolite flotation technologies and their characteristics. Traditional desliming-flotation operations can reduce slime effects but cause over 30% irreversible loss of fine-grained (<37 μm) lepidolite. Innovative viscous froth flotation and micro-nano bubble flotation improve the recovery of fine-grained lepidolite, but their industrial use is limited due to the sensitivity of the reagent system and high equipment energy consumption. For complex ores, efficient separation technology is needed to enhance fine particle surface hydrophobicity and to develop combined reagent systems with selective collection and pulp dispersion functions. Especially for ultrafine lepidolite, it is crucial to break traditional flotation boundaries, explore micro interface strengthening technology, recover all-size lepidolite, and drive the full utilization of lithium resources beyond the 90% technological barrier.

4. Lepidolite Flotation Reagent

As is well known, froth flotation is the core method for recovering lepidolite. Flotation separates target minerals from gangue by exploiting differences in their surface physical and chemical properties. Selective adsorption of flotation reagents enables this separation. Lepidolite flotation relies heavily on flotation reagents, with amine collectors being the classic choice. In addition, factors such as pulp concentration and temperature, as well as grinding particle size, can affect lepidolite flotation behavior.

4.1. Collectors

Interlayer potassium ions in the crystal structure of lepidolite are prone to hydrolysis and leaching. The oxygen and silicon atoms on its surface readily react with hydroxyl groups in solution, forming a stable hydroxylated surface structure. This gives lepidolite a negative charge across a wide pH range, allowing its collection using cationic reagents. Table 5 shows the structure and characteristics of traditional cationic reagents.

4.1.1. Primary Amine

Primary amines such as dodecylamine (DDA) and stearic amine are classic collectors widely used in lepidolite flotation. Lepidolite carries a negative charge between pH 2 and 12, and electrostatic interaction with amine cations increases its surface hydrophobicity. Lombe was among the first to use DDA for lepidolite flotation, achieving a good recovery at pH 11 with a DDA concentration of 3.10−5 M [83]. Most studies have been conducted under acidic conditions due to the significant difference in adsorption energy between DDA and lepidolite compared to other silicate gangue minerals. Huang et al. [58] used DDA as a collector at pH 3, with a reagent dosage of 350 g/t, yielding lepidolite concentrate with a Li2O grade of 4.05% and a recovery rate of 54.97%. Bhappu & Fuerstenau [74] found that using stearic amine as a collector, with a pH range of 2–4 and a reagent dosage of 340 g/t, could recover most of the lepidolite.

4.1.2. Secondary Amine

Choi first reported using stearyltrimethylammonium chloride (STAC) as a collector for lepidolite flotation. At a pH of around 2 and without any depressants, the Li2O grade reached a maximum of 2.77% [34]. The mechanism involves lepidolite surfaces being negatively charged and gangue surfaces positively charged at this pH. The reagent selectively adsorbs lepidolite through electrostatic interaction, increasing its hydrophobicity, while showing minimal interaction with the gangue, thus enabling selective separation. Additionally, Choi found that the Li2O grade decreases with increasing pH, while the recovery rate slightly increases. This may be because at higher pH levels, both lepidolite and gangue surfaces carry negative charges, reducing STAC selectivity between them.

4.1.3. Ether Amine

Ether amine collectors have better low-temperature performance and foaming properties than primary amine collectors, although less is reported, possibly due to limited availability or high costs.
Sousa et al. [81] floated the Gonçalo lepidolite deposit (Portugal) with Flotigam EDA (an ether amine) at pH~3.5 and 200 g/t dosage, yielding a high-lithium concentrate with 4.7% Li2O. At the same deposit, Filippov et al. [37] recovered fine-grained lepidolite using a mono-ether amine at pH~4 and 100 g/t dosage, obtaining lithium concentrate with 4.5% Li2O and 90% recovery rate.

4.1.4. Gemini Amine Collector

Gemini surfactants, with two hydrophilic and two hydrophobic groups, have unique solution properties. They show better water solubility and a Krafft point (a critical temperature where solubility changes significantly).
Huang et al. [82] were the first to study the effect of Gemini reagents on lepidolite flotation. They synthesized a Gemini collector, butanediyl-α,ω-bis-[dimethyldodecylammonium bromide] (BDB) (Figure 6). They applied this trapping agent to pure lepidolite mineral experiments and lithium-bearing lepidolite actual ore sample experiments, respectively. In the first experiment, a BDB dosage of only 1 · 10−4 M was used to achieve nearly 100% lepidolite recovery, while a DDA dosage of 6 · 10−4 M (6 times the BDB dosage) achieved nearly 90% lepidolite recovery. This indicates that the flotation effect of BDB is much higher than that of DDA under the condition of using a low dosage of chemicals. In the second experiment, they used BDB traps on actual ore samples under acidic conditions [58]. A Li2O grade of 4.12% and a recovery of 77.15% lithium concentrate were obtained with a BDB dosage of only 175 g/t. The BDB dosage of 350 g/t was used for the flotation of lepidolite, while the BDB dosage of 350 g/t was used for the flotation of lithium mica. In contrast, a Li2O grade of 4.05% and a recovery of 54.97% lithium concentrate were obtained at a BDB dosage of 350 g/t (twice that of BDB). This indicates that the recovery of low dosage of BDB is also higher than that of DDA in actual ores.

4.2. Combined Collector

Amine collectors, despite their effective flotation for lepidolite, often show poor selectivity. Recently, researchers have blended anionic and cationic collectors to form a combined reagent, enhancing mineral selectivity.
Qian et al. [40] combined SOL (a mixture of sodium dodecyl sulfonate and sodium oleate, with the former being twice the weight of the latter) with DDA for lepidolite-quartz separation. Their test material was an artificial mixture of lepidolite and quartz (mass ratio 1:1). At neutral pH with a SOL-DDA concentration ratio of 4:1, they obtained lithium concentrate with 4.99% Li2O and 96.35% recovery. In contrast, using DDA alone as a collector achieved a Li2O recovery of 95.82%, but the concentrate grade was only 2.63% (the original ore grade was 2.65%). This is because SOL hinders DDA adsorption on quartz but not lepidolite, thus enhancing the hydrophobicity of the lepidolite surface.
Yang et al. [84] used a mixture of sodium dodecyl sulfonate (SDS) and cetyltrimethylammonium bromide (CTAB) to separate the same artificial mineral mixture. At pH 7, with an SDS-CTAB concentration ratio of 6:1, the lithium concentrate achieved 5.16% Li2O and 91.17% recovery. FTIR and XPS analysis showed that SDS adsorbs more strongly on quartz. Together, they significantly increased the hydrophobicity of the target minerals.

4.3. Modifiers

In lepidolite flotation, modifiers are crucial auxiliary reagents that optimize mineral surface properties and pulp environment, directly impacting separation efficiency and concentrate grade. Lepidolite often coexists with gangue minerals such as quartz, feldspar, and calcite, whose similar surface electrochemical properties can lead to poor flotation selectivity. Modifiers can effectively regulate these surface properties, enhance selective adsorption of collectors, and improve lepidolite-gangue separation. Common modifiers include pH adjusters (e.g., H2SO4, NaOH), depressants (e.g., sodium silicate, starch), and activators (e.g., NaF, certain metal ions), which optimize flotation by altering pulp potential or selectively depressing gangue minerals. Developing efficient and eco-friendly modifiers is vital to advancing lepidolite flotation technology.

4.3.1. Activators

Lepidolite flotation rarely uses activators because amine collectors work well. However, non-amine collectors may require activators.
Deng et al. [85] used Ca2+ as an Activator and sodium lauroyl glutamate (SLG) as a green collector for lepidolite-albite flotation separation. At pH 5, with 2 · 10−4 M Ca2+ and 5 · 10−4 M SLG, they obtained lithium concentrate with 5.28% Li2O and 87.95% recovery. Without Ca2+, the lepidolite recovery dropped to about 35%. The mechanism of action is that Ca2+ combines with the O site of lepidolite, and the adsorption capacity of SLG with lepidolite is stronger than that of sodium feldspar, resulting in a shift from hydrophilic to hydrophobic surface of lepidolite. Xu et al. [86] used Mg2+ as an activator and NaOL as a collector for lepidolite-quartz separation. At pH 8, with 1.10−4 M Mg2+ and 3.10−4 M NaOL, they achieved a lithium concentrate with 5.38% Li2O and 98.13% recovery. These results show that suitable collectors and activators can effectively separate lepidolite from gangue minerals.

4.3.2. Depressants

In lepidolite flotation, depressant systems are divided into inorganic and organic types. Inorganic depressants, such as sodium silicate (water glass), mainly work by creating a hydrophilic layer on mineral surfaces or chelating metal cations, effectively inhibiting quartz, feldspar, and calcium-bearing gangue. However, their performance is highly pH-dependent (sodium silicate works best at pH 8–10) and requires high dosages. Organic depressants (e.g., starch, carboxymethyl cellulose) are widely available and more environmentally friendly [87,88], but their effectiveness can be influenced by ore composition and flotation conditions, making it difficult to precisely inhibit gangue minerals when used alone [89]. Therefore, the development of novel organic depressants with high selectivity and environmental compatibility is crucial for improving the quality of lepidolite concentrate.
Inorganic Depressants
Silicates and phosphates are commonly used as depressants in lepidolite flotation. Silicates mainly refer to water glass, while phosphates include sodium hexametaphosphate (SHMP). However, phosphate depressants are easily affected by competitive interference from divalent metal ions like Ca2+ and Mg2+ [90]. Their selectivity drops in ores with high calcium and magnesium content, and excessive use can cause environmental problems [91]. Therefore, in practical applications, it is necessary to combine water quality pretreatment with process parameter adjustments to overcome these limitations.
Water glass significantly affects the depression of silicate gangue minerals like quartz and feldspar in lepidolite flotation. With the chemical formula Na2OnSiO2, its modulus is represented by n. Studies show that when the modulus is low (n < 2.0), water glass is strongly alkaline (pH > 11), dispersing the pulp but weakly depressing gangue. When the modulus is too high (n > 3.0), its solubility and colloid stability decrease, resulting in uneven silicate film coverage on gangue surfaces [92]. In industrial lepidolite flotation, water glass with a modulus of 2.5–3.0 is commonly used. This maintains a moderate alkalinity (pH 8.5–10.5) and forms a stable hydrophilic silicate colloid layer, selectively depressing quartz, feldspar, and calcite [39].
For high-silicate lepidolite ores, traditional processes require high-temperature pulps (>70 °C) to enhance water-glass gangue depression, but this is energy-intensive and operationally complex. Recently, the “stepwise pulping” process has been proposed. Initially, water glass (modulus 2.8, 400–600 g/t) is added at low temperatures (25–35 °C) to depress quartz, then the temperature is raised to 50–60 °C to introduce a feldspar-specific depressant like modified lignosulfonate. Finally, with sodium carbonate (pH 9.5) and a fatty acid collector like sodium oleate, lepidolite recovery exceeds 85% [93]. However, this process is complex and costly. In a Jiangxi granite-type lepidolite deposit, a “one-rougher, two-scavenging, three–cleaning” closed-circuit process yielded lithium concentrate with 2.3% Li2O and 82.6% recovery, saving 30% energy compared to traditional methods [94]. By optimizing the water glass modulus and temperature response, this technology effectively depresses silicate gangue, providing new insights for complex lithium resource development.
Sodium hexametaphosphate (SHMP), with the chemical formula (NaPO3)6, is a common phosphate depressant. It selectively complexes with Ca2+ on calcium-bearing mineral surfaces through strong coordination, forming stable, insoluble complexes [95,96]. This reduces active metal sites and creates steric barriers to collector adsorption [97]. Specifically, PO3− groups bind to high-activity Ca2+ on gangue minerals like calcite and feldspar. The resulting Ca-PO3− complexes increase surface hydrophilicity and block collector-mineral interactions. In addition, SHMP acts as a dispersant. It disperses gangue minerals via electrostatic repulsion and steric hindrance, selectively complexes Ca2+/Mg2+ to depress slime aggregation, and reduces pulp viscosity. These combined effects enhance lepidolite flotation selectivity.
In recent years, Wang et al. [56] found that Fe3+ can be used as a selective depressant for feldspar and quartz in lepidolite flotation. In single mineral tests at pH = 4 with DDA as collector and 40 mg/L ferric chloride hexahydrate, lepidolite recovery reached 92.85%, while feldspar and quartz recovery remained below 20% (Figure 7) [56]. Tests such as adsorption amount and contact angle proved that Fe3+ adsorbed on the surface of gangue minerals, and the adsorption amount on the surface of gangue minerals was much larger than that of lepidolite. FTIR and XPS showed that the adsorption amount of DDA on the surface of gangue minerals was reduced due to the presence of Fe3+, without affecting the adsorption on the surface of lepidolite, due to the fact that gangue minerals have a more negative surface potential than lepidolite. This makes Fe3+ adsorption on the surface of gangue minerals selective on the minerals’ surface, hindering the adsorption of DDA with gangue minerals. The selective depression mechanism of Fe3+ on feldspar and quartz is depicted in Figure 8.
Organic Depressants
Organic depressants for lepidolite flotation typically include tannins, oxalic acid, and compounds based on lignin. Tannins, phenolic compounds from polyphenols and sugars, form a strong hydrophilic layer on quartz/feldspar surfaces through chemisorption and physisorption. Their phenolic hydroxyl groups also mask the hydrophobic collector layer on these minerals, strongly depressing them [98,99]. Oxalic acid complexes with metal ions on gangue minerals, creating insoluble metal complexes (e.g., CaC2O4) that enhance surface hydrophilicity [100,101,102]. Lignin derivatives disperse mineral particles in pulp by electrostatic repulsion, reducing aggregation. They selectively adsorb into silicate minerals to depress their floatability and remove clay coatings from lepidolite surfaces, thus enhancing collector interaction with lepidolite [103,104].
Combined Depressants
Recent studies have shown that in lepidolite flotation systems, collaborative interface regulation of multi-component depressants can achieve selective depression of silicate gangue minerals. For example, for the flotation system of high-grade lepidolite ore in Yichun, Jiangxi, Zhou and others developed a compound depressant ZY composed of tartaric acid, starch, and kerosene. This system, through metal ion chelation of tartaric acid, selective depression of aluminum silicates by starch, and hydrophobic synergistic effect of kerosene, successfully realized the efficient separation of lepidolite from associated minerals. From ore with a Li2O grade of 0.64%, it achieved excellent results of 3.62% Li2O in concentrate and a recovery rate of 78.53%, significantly outperforming traditional single-depressant systems [105]. For resource utilization of tantalum niobium tailings, Liu’s research team constructed a compound depressant system of sodium silicate, sodium phosphate, and carboxymethyl cellulose. By optimizing their mass ratios (1:1:3, 1:1:2, 3:1:6), they enhanced the flotation separation efficiency of lepidolite and associated minerals. In fine grained lepidolite flotation, Jiao’s team developed a high pulp concentration process using a sodium hexametaphosphate sodium silicate compound depressant (mass ratio 2:1). This system uses the strong dispersion of sodium hexametaphosphate and the selective adsorption of sodium silicate to prevent the hydrophobicity of gangue minerals such as quartz and feldspar, effectively controlling the dispersion of fine-grained mineral particles. For lepidolite ore flotation, Feng’s group designed a synergistic alkaline adjuster system of sodium carbonate-sodium silicate (55%–65% sodium carbonate). Through the synergistic effect of the pH buffering effect of sodium carbonate and the silicate depressing function of sodium silicate, slurry dispersion was successfully regulated, and the difference in surface wettability between lepidolite and clay minerals was strengthened, and finally, froth flotation and efficient separation of high clay ores were realized. However, the available research data confirm that the synergistic depressing effect of the depressant system is mainly achieved by combining the characteristics of different types of depressants. This depressing effect increases the wettability difference between lepidolite and associated minerals through complementary mechanisms such as metal ion chelation, selective adsorption, and interfacial charge modulation, and achieves efficient separation of lepidolite and gangue minerals. Table 6 summarizes the current depressants for lithium mica flotation and their mechanisms of action.

5. Challenges in Lepidolite-Gangue Minerals Separation

5.1. Similar Physical Properties of Lepidolite and Gangue Minerals

Lepidolite’s main gangue minerals are silicates, which share similar physicochemical properties with lepidolite. Lepidolite is non-magnetic or weakly magnetic (except for iron-bearing lepidolite), and quartz and feldspar are also nearly non-magnetic. Thus, separation by appearance or magnetic methods is challenging. Additionally, both lepidolite and gangue minerals have isoelectric points (IEP) near pH 2 and exhibit similar electrokinetic properties [40]. Their surfaces are negatively charged across most pH values. As shown in Figure 9 [40], similar zeta potentials of these minerals indicate that separating lepidolite from gangue is highly challenging. Zeta potential, a key parameter for mineral surface characterization, further highlights this difficulty.

5.2. Physical Limitations of Microfine Particle Embedding and Susceptibility to Sludging

In granite pegmatite deposits, lepidolite typically forms scaly aggregates and creates a micron-scale interlayered structure with quartz and feldspar (ore-embedding size of 10–50 μm). Its perfect (0 0 1) cleavage makes it highly prone to interlayer stripping during crushing, generating a large amount of ultra-fine particles (content of particles < 10 μm exceeds 35%) [106]. These flaky particles have a specific surface area of approximately 10 m2/g, which significantly raises pulp viscosity and triggers a fine-slime-coating effect. As a result, the contact path between collectors and active sites, such as K+ interlayer vacancies, becomes blocked.

5.3. Similarity Interference Between Mineral Crystal Chemistry and Surface Properties

Lepidolite, muscovite, and ferrous lepidolite are dioctahedral layered silicates. The overlapping densities of lepidolite and muscovite range from 2.76–3.00 g/cm3, and both have similar IEPs and crystal structures [106]. This makes the adsorption energy of amines like DDA comparable on both minerals. Also, isomorphous substitution causes continuous variation in layer charge density, leading to significant differences in lepidolite flotation behavior across regions.

5.4. Interfacial Chemical Contamination Induced by Reactivity of Gangue Minerals

Preferential dissolution of feldspar in a weakly acidic environment (pH~4) is a key source of interference. It releases Al3+ and Ca3+ ions, which generate colloidal particles [Al(OH)3]n and [CaSO4], which are tightly adsorbed on the crystal surface of lepidolite (0 0 1) through hydrogen bonding, forming a contamination layer [107]. This process resulted in a significant decrease in the contact angle of the lepidolite surface and a decrease in the amount of amine trap adsorption.

6. Conclusions and Future Outlook

As an important lithium resource, lepidolite faces multiple challenges in its flotation recovery. Studies have confirmed that traditional cation can effectively recover lepidolite, but it is limited by the strong acidic environment, and the surface characteristics of lepidolite and quartz, feldspar, and other gangue minerals are similar, so the process selectivity is poor. Neutral or weakly alkaline conditions using an anion/cation combination of recovery agent is more effective, but the mechanism of interaction with minerals is not well studied, and the sludge interference is large. Industrially, lithium lepidolite deposits are accompanied by a large amount of fine mud, and the desliming process leads to a serious loss of fine-grained lepidolite. For the bottleneck of fine-grained recovery, flocculation flotation and micro-nano-bubble flotation technology show breakthrough potential, but their industrialization needs to overcome the precise control of pharmaceuticals and the stability of slurry flow problems.
Summarizing the current research progress of lepidolite flotation technology, the following three aspects may be the key direction of lepidolite research in the future.
(1) Aiming at the low selectivity problem caused by the similarity between the surface properties of lepidolite and chondritic minerals, it is necessary to develop a combination of highly selective and environmentally adapted pharmaceutical systems. Focus on the study of anion/cation synergistic trapping agent interfacial adsorption kinetics, to achieve the hydrophobicity of the surface of lepidolite directional regulation, while reducing the dependence on pH.
(2) Tackle the problem of fine-grained lepidolite loss caused by pre-desliming mud, develop micro-fine-grained directional recovery technology based on interfacial chemical regulation and the development of selective flocculants, and break through the particle size limitation of traditional flotation.
(3) Aiming at the complex associated deposits of lepidolite, construct the magnetic-flotation-heavy-electricity joint sorting process, and introduce machine learning to optimize the sorting parameters in real time. Through online mineral analysis technology, we dynamically adjust the pharmaceutical system, magnetic field strength, and sorting process to realize efficient recovery of lepidolite in all grain sizes.

Author Contributions

X.Y. conceptualized the study, finalized the manuscript. B.F. developed and analyzed. L.J. edited the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

The authors acknowledge the financial support of the key basic research project of Yichun City (Project 2023ZDJCYJ01).

Data Availability Statement

The original contributions presented in the study are included in the article; further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors state that they have no known competing financial interests or personal relationships that could have influenced this paper.

References

  1. Kim, T.; Song, W.; Son, D.-Y.; Ono, L.K.; Qi, Y. Lithium-ion batteries: Outlook on present, future, and hybridized technologies. J. Mater. Chem. A 2019, 7, 2942–2964. [Google Scholar] [CrossRef]
  2. Vikström, H.; Davidsson, S.; Höök, M. Lithium availability and future production outlooks. Appl. Energy 2013, 110, 252–266. [Google Scholar] [CrossRef]
  3. Speirs, J.; Contestabile, M.; Houari, Y.; Gross, R. The future of lithium availability for electric vehicle batteries. Renew. Sustain. Energy Rev. 2014, 35, 183–193. [Google Scholar] [CrossRef]
  4. Martins, L.S.; Guimarães, L.F.; Junior, A.B.B.; Tenório, J.A.S.; Espinosa, D.C.R. Electric car battery: An overview on global demand, recycling and future approaches towards sustainability. J. Environ. Manag. 2021, 295, 113091. [Google Scholar] [CrossRef] [PubMed]
  5. Bruce, G.C.; Marcoux, L. Large lithium ion batteries for aerospace and aircraft applications. In Proceedings of the Sixteenth Annual Battery Conference on Applications and Advances, Long Beach, CA, USA, 12 January 2001; IEEE: New York, NY, USA; pp. 147–151. [Google Scholar]
  6. Labbé, J.-F.; Daw, G. Panorama 2011 du marché du lithium. In Bureau de Recherches Géologiques et Minières; Centre D’économie de la Sorbonne: Paris, France, 2012. [Google Scholar]
  7. Christmann, P.; Gloaguen, E.; Labbé, J.-F.; Melleton, J.; Piantone, P. Global lithium resources and sustainability issues. In Lithium Process Chemistry; Elsevier: Amsterdam, The Netherlands, 2015; pp. 1–40. [Google Scholar]
  8. Garrett, D.E. Handbook of Lithium and Natural Calcium Chloride; Elsevier: Amsterdam, The Netherlands, 2004. [Google Scholar]
  9. Swain, B. Recovery and recycling of lithium: A review. Sep. Purif. Technol. 2017, 172, 388–403. [Google Scholar] [CrossRef]
  10. Delgado, M.; Valencia, C.; Sánchez, M.; Franco, J.; Gallegos, C. Thermorheological behaviour of a lithium lubricating grease. Tribol. Lett. 2006, 23, 47–54. [Google Scholar] [CrossRef]
  11. Wang, J.; Zhao, Y.; Li, G.; Luo, D.; Liu, J.; Zhang, Y.; Wang, X.; Shui, L.; Chen, Z. Aligned sulfur-deficient ZnS1−x nanotube arrays as efficient catalyzer for high-performance lithium/sulfur batteries. Nano Energy 2021, 84, 105891. [Google Scholar] [CrossRef]
  12. Phark, J.H.; Duarte, S., Jr. Microstructural considerations for novel lithium disilicate glass ceramics: A review. J. Esthet. Restor. Dent. 2022, 34, 92–103. [Google Scholar] [CrossRef]
  13. Gloaguen, E.; Melleton, J.; Lefebvre, G.; Tourlière, B.; Yart, S.; Gourcerol, B. Ressources Métropolitaines en Lithium et Analyse du Potentiel par Méthodes de Prédictivité; BRGM: Orleans, France, 2018; p. 126. [Google Scholar]
  14. Sousa, R.; Ramos, V.; Guedes, A.; de Sousa, A.B.; Noronha, F.; Leite, M.M. Flotation of lithium ores to obtain high-grade Li2O concentrates. Are there any mineralogical limitations? Int. J. Min. Mater. Metall. Eng. 2019, 5, 7–18. [Google Scholar]
  15. Singer, D.A. Future copper resources. Ore Geol. Rev. 2017, 86, 271–279. [Google Scholar] [CrossRef]
  16. Kavanagh, L.; Keohane, J.; Garcia Cabellos, G.; Lloyd, A.; Cleary, J. Global lithium sources—Industrial use and future in the electric vehicle industry: A review. Resources 2018, 7, 57. [Google Scholar] [CrossRef]
  17. Helvaci, C.; Mordogan, H.; Çolak, M.; Gündogan, I. Presence and distribution of lithium in borate deposits and some recent lake waters of west-central Turkey. Int. Geol. Rev. 2004, 46, 177–190. [Google Scholar] [CrossRef]
  18. Friedman-Rudovsky, J. Dreams of a Lithium Empire; American Association for the Advancement of Science: New York, NY, USA, 2011. [Google Scholar]
  19. Kesler, S.E.; Gruber, P.W.; Medina, P.A.; Keoleian, G.A.; Everson, M.P.; Wallington, T.J. Global lithium resources: Relative importance of pegmatite, brine and other deposits. Ore Geol. Rev. 2012, 48, 55–69. [Google Scholar] [CrossRef]
  20. Ebensperger, A.; Maxwell, P.; Moscoso, C. The lithium industry: Its recent evolution and future prospects. Resour. Policy 2005, 30, 218–231. [Google Scholar] [CrossRef]
  21. Gruber, P.W.; Medina, P.A.; Keoleian, G.A.; Kesler, S.E.; Everson, M.P.; Wallington, T.J. Global lithium availability: A constraint for electric vehicles? J. Ind. Ecol. 2011, 15, 760–775. [Google Scholar] [CrossRef]
  22. Tkachev, A.; Rundqvist, D.; Vishnevskaya, N. Metallogeny of lithium through geological time. Russ. J. Earth Sci. 2018, 18, 1–12. [Google Scholar] [CrossRef]
  23. Sharma, H.; Sharma, S.; Mishra, P.K. A critical review of recent progress on lithium ion batteries: Challenges, applications, and future prospects. Microchem. J. 2025, 212, 113494. [Google Scholar] [CrossRef]
  24. Bowell, R.J.; Lagos, L.; de los Hoyos, C.R.; Declercq, J. Classification and characteristics of natural lithium resources. Elements 2020, 16, 259–264. [Google Scholar] [CrossRef]
  25. Naumov, A.; Naumova, M. Modern state of the world lithium market. Russ. J. Non-Ferr. Met. 2010, 51, 324–330. [Google Scholar] [CrossRef]
  26. Dorn, F.M.; Peyré, F.R. Lithium as a Strategic Resource. J. Lat. Am. Geogr. 2020, 19, 68–90. [Google Scholar] [CrossRef]
  27. Li, H.; Eksteen, J.; Kuang, G. Recovery of lithium from mineral resources: State-of-the-art and perspectives—A review. Hydrometallurgy 2019, 189, 105129. [Google Scholar] [CrossRef]
  28. Zhuo, W.; Ranxiao, H.; Datian, W.; Fengming, X.; Wei, S.; Dehui, Z.; Yuandong, Z. The basic characteristics and development potential evaluation of salt lake brine-type lithium deposits. Geol. China 2023, 50, 102–117. [Google Scholar]
  29. Tadesse, B.; Makuei, F.; Albijanic, B.; Dyer, L. The beneficiation of lithium minerals from hard rock ores: A review. Miner. Eng. 2019, 131, 170–184. [Google Scholar] [CrossRef]
  30. Reichel, S.; Aubel, T.; Patzig, A.; Janneck, E.; Martin, M. Lithium recovery from lithium-containing micas using sulfur oxidizing microorganisms. Miner. Eng. 2017, 106, 18–21. [Google Scholar] [CrossRef]
  31. Liu, K. Research Progress in flotation collectors for lepidolite mineral: An overview. Miner. Process. Extr. Metall. Rev. 2024, 45, 728–742. [Google Scholar] [CrossRef]
  32. Brown, B. The crystal structure of a 3lepidolite. Am. Mineral. 1978, 63, 332–336. [Google Scholar]
  33. Tian, J.; Xu, L.; Wu, H.; Fang, S.; Deng, W.; Peng, T.; Sun, W.; Hu, Y. A novel approach for flotation recovery of spodumene, mica and feldspar from a lithium pegmatite ore. J. Clean. Prod. 2018, 174, 625–633. [Google Scholar] [CrossRef]
  34. Choi, J.; Kim, W.; Chae, W.; Kim, S.B.; Kim, H. Electrostatically controlled enrichment of lepidolite via flotation. Mater. Trans. 2012, 53, 2191–2194. [Google Scholar] [CrossRef]
  35. Choubey, P.K.; Kim, M.-s.; Srivastava, R.R.; Lee, J.-c.; Lee, J.-Y. Advance review on the exploitation of the prominent energy-storage element: Lithium. Part I: From mineral and brine resources. Miner. Eng. 2016, 89, 119–137. [Google Scholar] [CrossRef]
  36. Yan, Q.; Li, X.; Wang, Z.; Wu, X.; Wang, J.; Guo, H.; Hu, Q.; Peng, W. Extraction of lithium from lepidolite by sulfation roasting and water leaching. Int. J. Miner. Process. 2012, 110, 1–5. [Google Scholar] [CrossRef]
  37. Filippov, L.O.; Filippova, I.V.; Crumiere, G.; Sousa, R.; Leite, M.M.; de Sousa, A.B.; Korbel, C.; Tripathy, S.K. Separation of lepidolite from hard-rock pegmatite ore via dry processing and flotation. Miner. Eng. 2022, 187, 107768. [Google Scholar] [CrossRef]
  38. Tang, Y.; Zhang, Q.; Yang, W.; Miao, Y.; Feng, Q. A novel combined collector with superior selectivity for flotation separation of lepidolite from feldspar: Experimental insight and MD simulation. Sep. Purif. Technol. 2024, 347, 127627. [Google Scholar] [CrossRef]
  39. Jiao, F.; Zhang, Z.; Wei, Q.; Qin, W. Key technologies and development trends for efficient flotation recovery of lepidolite. Green Smart Min. Eng. 2024, 1, 273–288. [Google Scholar] [CrossRef]
  40. Wei, Q.; Feng, L.; Dong, L.; Jiao, F.; Qin, W. Selective co-adsorption mechanism of a new mixed collector on the flotation separation of lepidolite from quartz. Colloids Surf. A Physicochem. Eng. Asp. 2021, 612, 125973. [Google Scholar] [CrossRef]
  41. Overhauser, A. Crystal structure of lithium at 4.2 K. Phys. Rev. Lett. 1984, 53, 64. [Google Scholar] [CrossRef]
  42. Guo, H.; Kuang, G.; Wan, H.; Yang, Y.; Yu, H.-z.; Wang, H.-d. Enhanced acid treatment to extract lithium from lepidolite with a fluorine-based chemical method. Hydrometallurgy 2019, 183, 9–19. [Google Scholar] [CrossRef]
  43. Zeng, Q.; Li, S.; Sun, W.; Hu, L.; Zhong, H.; He, Z. Eco-friendly leaching of rubidium from biotite-containing minerals with oxalic acid and effective removal of Hg2+ from aqueous solution using the leaching residues. J. Clean. Prod. 2021, 306, 127167. [Google Scholar] [CrossRef]
  44. Mulwanda, J.; Senanayake, G.; Oskierski, H.; Altarawneh, M.; Dlugogorski, B.Z. Leaching of lepidolite and recovery of lithium hydroxide from purified alkaline pressure leach liquor by phosphate precipitation and lime addition. Hydrometallurgy 2021, 201, 105538. [Google Scholar] [CrossRef]
  45. Zhang, X.; Tan, X.; Li, C.; Yi, Y.; Liu, W.; Zhang, L. Energy-efficient and simultaneous extraction of lithium, rubidium and cesium from lepidolite concentrate via sulfuric acid baking and water leaching. Hydrometallurgy 2019, 185, 244–249. [Google Scholar] [CrossRef]
  46. Yan, Q.; Li, X.; Wang, Z.; Wu, X.; Guo, H.; Hu, Q.; Peng, W.; Wang, J. Extraction of valuable metals from lepidolite. Hydrometallurgy 2012, 117, 116–118. [Google Scholar] [CrossRef]
  47. Radoslovich, E. The structure of muscovite, KAl2(Si3Al)O10(OH)2. Acta Crystallogr. 1960, 13, 919–932. [Google Scholar] [CrossRef]
  48. Jackson, W.; West, J. The Crystal Structure of Muscovite—ΚAl2(AlSi3)O10(OH)2. Z. Krist.–Cryst. Mater. 1931, 76, 211–227. [Google Scholar] [CrossRef]
  49. Güven, Ν.; Burnham, C.W. The crystal structure of 3Τ muscovite. Z. Krist.–Cryst. Mater. 1967, 125, 163–183. [Google Scholar] [CrossRef]
  50. Tressaud, A.; Labrugère, C.; Durand, E.; Serier, H.; Demyanova, L.P. Surface modification of phyllosilicate minerals by fluorination methods. J. Vac. Sci. Technol. A 2010, 28, 373–381. [Google Scholar] [CrossRef]
  51. Evans, S.; Raftery, E. X-ray photoelectron diffraction studies of lepidolite. Clay Miner. 1982, 17, 443–452. [Google Scholar] [CrossRef]
  52. Stevens, R.E. New analyses of lepidolites and their interpretation. Am. Mineral. J. Earth Planet. Mater. 1938, 23, 607–628. [Google Scholar]
  53. Winchell, A. Further studies of the lepidolite system. Am. Mineral. J. Earth Planet. Mater. 1942, 27, 114–130. [Google Scholar]
  54. Korbel, C.; Demeusy, B.; Kahou, Z.S.; Filippova, I.V.; Dehaine, Q.; Filippov, L.O. Flowsheet development for the selective flotation of lepidolite from the Beauvoir granite from mineralogical insights. Miner. Eng. 2025, 225, 109207. [Google Scholar] [CrossRef]
  55. Aylmore, M.G.; Merigot, K.; Quadir, Z.; Rickard, W.D.A.; Evans, N.J.; McDonald, B.J.; Catovic, E.; Spitalny, P. Applications of advanced analytical and mass spectrometry techniques to the characterisation of micaceous lithium-bearing ores. Miner. Eng. 2018, 116, 182–195. [Google Scholar] [CrossRef]
  56. Wang, F.; Liu, L.; Zhang, J.; Cao, Y.; He, J.; Li, G. Selective Inhibition Mechanisms of Fe (III) in the Flotation of Lepidolite. Minerals 2024, 14, 851. [Google Scholar] [CrossRef]
  57. He, J.; Xu, H.; Yang, B.; Gong, W.; Zhang, Z.; Shan, Y.; Song, T. Adsorption properties of an efficient combined collector and its enhanced separation of lepidolite from feldspar. J. Ind. Eng. Chem. 2025, 148, 797–808. [Google Scholar] [CrossRef]
  58. Huang, Z.; Shuai, S.; Wang, H.; Liu, R.; Zhang, S.; Cheng, C.; Hu, Y.; Yu, X.; He, G.; Fu, W. Froth flotation separation of lepidolite ore using a new Gemini surfactant as the flotation collector. Sep. Purif. Technol. 2022, 282, 119122. [Google Scholar] [CrossRef]
  59. Belyankina, Y.D.; Petrov, V. Geochemical role of micas in mineral associations: Classification, chemistry, and genesis of micas. Int. Geol. Rev. 1983, 25, 993–1003. [Google Scholar] [CrossRef]
  60. Brigatti, M.F.; Kile, D.E.; Poppi, M. Crystal structure and crystal chemistry of lithium-bearing muscovite-2M1. Can. Mineral. 2001, 39, 1171–1180. [Google Scholar] [CrossRef]
  61. Chardon, E.S.; Livens, F.R.; Vaughan, D.J. Reactions of feldspar surfaces with aqueous solutions. Earth-Sci. Rev. 2006, 78, 1–26. [Google Scholar] [CrossRef]
  62. Smith, J.V. Feldspar Minerals: 1 Crystal Structure and Physical Properties; Springer Science & Business Media: Berlin/Heidelberg, Germany, 2013. [Google Scholar]
  63. Blum, A.E.; Stillings, L.L. Feldspar dissolution kinetics. Rev. Mineral. 1995, 31, 291–352. [Google Scholar]
  64. Heyes, G.; Allan, G.; Bruckard, W.; Sparrow, G. Review of flotation of feldspar. Miner. Process. Extr. Metall. 2012, 121, 72–78. [Google Scholar] [CrossRef]
  65. Ribbe, P. Chemistry, structure and nomenclature of feldspars. Feldspar Mineral. 1983, 2, 1–20. [Google Scholar]
  66. Smith, J.V. Feldspar Minerals: 2 Chemical and Textural Properties; Springer Science & Business Media: Berlin/Heidelberg, Germany, 2012. [Google Scholar]
  67. Harris, M.J.; Salje, E.K.; Guttler, B.K.; Carpenter, M.A. Structural states of natural potassium feldspar: An infrared spectroscopic study. Phys. Chem. Miner. 1989, 16, 649–658. [Google Scholar] [CrossRef]
  68. Götze, J.; Pan, Y.; Müller, A. Mineralogy and mineral chemistry of quartz: A review. Mineral. Mag. 2021, 85, 639–664. [Google Scholar] [CrossRef]
  69. Pan, X.; Li, S.; Li, Y.; Guo, P.; Zhao, X.; Cai, Y. Resource, characteristic, purification and application of quartz: A review. Miner. Eng. 2022, 183, 107600. [Google Scholar] [CrossRef]
  70. Rahimi, M.; Dehghani, F.; Rezai, B.; Aslani, M.R. Influence of the roughness and shape of quartz particles on their flotation kinetics. Int. J. Miner. Metall. Mater. 2012, 19, 284–289. [Google Scholar] [CrossRef]
  71. Larsen, E.; Kleiv, R. Flotation of quartz from quartz-feldspar mixtures by the HF method. Miner. Eng. 2016, 98, 49–51. [Google Scholar] [CrossRef]
  72. Swanepoel, A.J.; Rees, D.; Renton, K.; Swanepoel, C.; Kromhout, H.; Gardiner, K. Quartz exposure in agriculture: Literature review and South African survey. Ann. Occup. Hyg. 2010, 54, 281–292. [Google Scholar] [CrossRef]
  73. Raman, C.; Nedungadi, T. The α-β transformation of quartz. Nature 1940, 145, 147. [Google Scholar] [CrossRef]
  74. Bhappu, R.; Fuerstenau, D. Recovery of valuable minerals from pegmatitic ores. In Circular; New Mexico Bureau of Geology & Mineral Resources: Socorro, NM, USA, 1964; Volume 70, p. 29. [Google Scholar]
  75. Bai, Y.; Cui, W.; Gao, Y.; Wen, W.; Sun, Y.; Yan, P. Synergistic mechanism of mixed cationic/anionic collectors on lepidolite flotation from the perspective of improving the performance of flotation foam. Colloids Surf. A Physicochem. Eng. Asp. 2023, 656, 130354. [Google Scholar] [CrossRef]
  76. Liu, Z.; Jiao, F.; Qin, W.; Wei, Q. Collision–attachment law of lepidolite, feldspar and quartz with bubbles in the combined cationic and anionic collector system. Physicochem. Probl. Miner. Process. 2022, 58, 155324. [Google Scholar] [CrossRef]
  77. Zhang, Z.; Wei, Q.; Jiao, F.; Qin, W. Role of nanobubbles on the fine lepidolite flotation with mixed cationic/anionic collector. Powder Technol. 2023, 427, 118785. [Google Scholar] [CrossRef]
  78. Chen, H.; Sun, A.; Liao, M.; Zhao, H.; Zhong, H. A Method for Flotation of Lepidolite Without Desliming. CN Patent CN115608520A, 17 January 2023. [Google Scholar]
  79. Ai, W.; Xiong, H.; Yang, J.; Yan, Z.; Yi, Y.; Xiong, S. A Method for Recovering Lepidolite Concentrate from Lepidolite Ore Tailings. CN Patent CN114713364B, 24 November 2023. [Google Scholar]
  80. Peng, S.; Wang, Z.; Zhao, H.; Liu, F.; Wang, Q.; Lu, H.; Wei, S.; Dou, H.; Wang, B.; Bai, Z.; et al. Experimental research on compre-hensive mineral processing of lepidolite and feldspar in Hunan Province. Ceramics 2024, 1, 38–41. [Google Scholar] [CrossRef]
  81. Sousa, R.; Ramos, V.; Guedes, A.; Noronha, F.; Botelho de Sousa, A.; Machado Leite, M.; Seltmann, R.; Dolgopolova, A. The Alvarrões-Gonçalo Li project: An example of sustainable lithium mining. Adv. Geosci. 2018, 45, 1–5. [Google Scholar] [CrossRef]
  82. Huang, Z.; Zhang, S.; Cheng, C.; Wang, H.; Liu, R.; Hu, Y.; He, G.; Yu, X.; Fu, W. Recycling lepidolite from tantalum–niobium mine tailings by a combined magnetic–flotation process using a novel gemini surfactant: From tailings dams to the “bling” raw material of lithium. ACS Sustain. Chem. Eng. 2020, 8, 18206–18214. [Google Scholar] [CrossRef]
  83. Lombe, W. The Surface Chemistry Spodumene, Lepidolite and in the Presence of and Flotation of Associate d Silicates Dodecylamine. Ph.D. Thesis, University of London, London, UK, 1983. [Google Scholar]
  84. Yang, Z.; Xu, H.; Tang, X.; Zhou, H.; Xie, T.; Shen, L.; Guo, L.; Luo, X. Application of a novel mixed anionic/cationic collector in the selective flotation separation of lepidolite and quartz. Colloids Surf. A Physicochem. Eng. Asp. 2024, 701, 134919. [Google Scholar] [CrossRef]
  85. Deng, Y.; Ou, L. Mechanism for the selective separation of lepidolite from albite by sodium lauroyl glutamate as a green environment collector. Colloids Surf. A Physicochem. Eng. Asp. 2024, 701, 134922. [Google Scholar] [CrossRef]
  86. Xu, R.; Liu, Y.; Sun, N.; Kang, J.; Sun, W.; Tang, H.; Wang, L. The activation role of Mg2+ in the lepidolite flotation using NaOL. Sep. Purif. Technol. 2024, 351, 128035. [Google Scholar] [CrossRef]
  87. Silva, E.M.S.; Peres, A.E.C.; Silva, A.C.; Florêncio, D.L.; Caixeta, V.H. Sorghum starch as depressant in mineral flotation: Part 2—Flotation tests. J. Mater. Res. Technol. 2019, 8, 403–410. [Google Scholar] [CrossRef]
  88. Ayedzi, L.D.; Zanin, M.; Skinner, W.; Wood, G.B.A. Minimizing entrainment recovery of ultrafine silicate minerals in pentlandite flotation using carboxymethyl cellulose. Miner. Eng. 2024, 217, 108942. [Google Scholar] [CrossRef]
  89. Ma, S.; Deng, J.; Xing, D.; Huang, G.; Cheng, T.; Zhang, D.; Deng, J.; Zhong, W.; Leng, X.; Quan, B. Study on the influence of graphite and sphalerite flotation separation by carboxymethyl cellulose. Sep. Purif. Technol. 2025, 355, 129577. [Google Scholar] [CrossRef]
  90. Cruz, D.G.d.; Alves, M.O.; Lima, R.M.F. Effect of Sodium Hexametaphosphate on Flotation of Quartz and Hematite with Starch/Etheramine in the Presence of Ca and Mg Ions. Miner. Process. Extr. Metall. Rev. 2024, 45, 950–956. [Google Scholar] [CrossRef]
  91. Kumar, S.J.; Han-Seung, L. Enhanced corrosion resistance properties of 15Al-85Zn coating by post-treatment with sodium hexa-meta phosphate in saline solution. Corros. Sci. 2024, 226, 111684. [Google Scholar]
  92. Silva, J.P.; Baltar, C.; Gonzaga, R.; Peres, A.; Leite, J. Identification of sodium silicate species used as flotation depressants. Min. Metall. Explor. 2012, 29, 207–210. [Google Scholar] [CrossRef]
  93. Krishnan, R.; Gopan, G. A comprehensive review of lithium extraction: From historical perspectives to emerging technologies, storage, and environmental considerations. Clean. Eng. Technol. 2024, 20, 100749. [Google Scholar] [CrossRef]
  94. Xu, L.; Wang, S.; Xu, J.; Wang, H.; Chao, W.; Lu, W.; Zhou, B.; Yang, S.; Hu, N. Lithium occurrences and enrichment of granite regolith-hosted Li deposits in Jiangxi Province, South China: An example of the Xikeng Li deposit. Ore Geol. Rev. 2024, 169, 106104. [Google Scholar] [CrossRef]
  95. Ramirez, A.; Rojas, A.; Gutierrez, L.; Laskowski, J.S. Sodium hexametaphosphate and sodium silicate as dispersants to reduce the negative effect of kaolinite on the flotation of chalcopyrite in seawater. Miner. Eng. 2018, 125, 10–14. [Google Scholar] [CrossRef]
  96. Qin, W.; Hu, J.; Zhu, H.; Jiao, F.; Jia, W.; Han, J.; Chen, C. Effect of depressants on flotation separation of magnesite from dolomite and calcite. Int. J. Min. Sci. Technol. 2023, 33, 83–91. [Google Scholar] [CrossRef]
  97. Ding, H.; Lin, H.; Deng, Y. Depressing effect of sodium hexametaphosphate on apatite in flotation of rutile. J. Univ. Sci. Technol. Beijing Miner. Metall. Mater. 2007, 14, 200–203. [Google Scholar] [CrossRef]
  98. Matveeva, T.; Gromova, N.; Lantsova, L. Effect of tannin on compound collector adsorption and stibnite and arsenopyrite flotation from complex ore. J. Min. Sci. 2017, 53, 1108–1115. [Google Scholar] [CrossRef]
  99. Gong, X.; Yao, J.; Guo, J.; Yang, B.; Sun, H.; Yin, W.; Wang, Y.; Fu, Y. Role of tannin pretreatment in flotation separation of magnesite and dolomite. Int. J. Miner. Metall. Mater. 2024, 31, 452–461. [Google Scholar] [CrossRef]
  100. Zhu, X.; Huang, Y.; Zhu, Y.; Sun, N.; Wang, W. Investigating the performance of oxalic acid for separating bastnaesite from calcium-bearing gangue minerals based on experiment and theoretical calculation. Miner. Eng. 2021, 170, 107047. [Google Scholar] [CrossRef]
  101. Liu, J.; Yuan, S.; Han, Y.; Li, Y. The effects of various activators on flotation performance of lime-depressed pyrrhotite. Can. Metall. Q. 2019, 58, 132–139. [Google Scholar] [CrossRef]
  102. Li, H.; Chai, W.; Cao, Y.; Yang, S. Flotation enhancement of low-grade bauxite using oxalic acid as surface pretreatment agent. Appl. Surf. Sci. 2022, 577, 151964. [Google Scholar] [CrossRef]
  103. Yang, X.; Bao, J.; Liu, Z.; Wu, D.; Cao, Y.; Xu, C.C.; Hao, H.; Zhang, Y. Synthesis of sulfomethylated depolymerized alkali lignin and its application in scheelite flotation. J. Mol. Liq. 2025, 424, 127102. [Google Scholar] [CrossRef]
  104. Qian, H.; Bao, J.; Shen, C.; Wu, D.; Wang, J.; Hao, H.; Zhang, Y. Improved flotation separation of scheelite from calcite by sulfomethylated kraft lignin. Materials 2023, 16, 4690. [Google Scholar] [CrossRef]
  105. Zhou, H.; Zhang, Y.; Lei, M.; Liu, Y.; Du, X.; Geng, L. Flotation separation test of zinnwaldite in Yichun of Jiangxi. Non Met. Ores 2019, 42, 64–67. [Google Scholar]
  106. Ahmad, S.S.; Yongjun, S.; Yu, Z.; Hongtao, Z.; Lianjie, Z. Texture and Trace Element Geochemistry of Quartz: A Review. Minerals 2022, 12, 1042. [Google Scholar] [CrossRef]
  107. Chen, M.; Zhao, L.; Huang, Y.; Fu, L.; Ma, L.; Chen, K.; Gu, Z. Review on K-Feldspar Mineral Processing for Extracting Metallic Potassium as a Fertilizer Resource. Minerals 2024, 14, 168. [Google Scholar] [CrossRef]
Minerals 15 00750 g001
Figure 1. Distribution of world lithium resources in 2022.
Figure 1. Distribution of world lithium resources in 2022.
Minerals 15 00750 g001
Minerals 15 00750 g002
Figure 2. Schematic diagram of the crystal structure of lepidolite [39]. Atomic colors: purple—potassium, red—oxygen, green—lithium, blue—aluminum.
Figure 2. Schematic diagram of the crystal structure of lepidolite [39]. Atomic colors: purple—potassium, red—oxygen, green—lithium, blue—aluminum.
Minerals 15 00750 g002
Minerals 15 00750 g003
Figure 3. Zeta potential of lepidolite as a function of pH.
Figure 3. Zeta potential of lepidolite as a function of pH.
Minerals 15 00750 g003
Minerals 15 00750 g004
Figure 4. Polytypes of muscovite transformation process.
Figure 4. Polytypes of muscovite transformation process.
Minerals 15 00750 g004
Minerals 15 00750 g005
Figure 5. Flow chart for processing difficult-to-select lepidolite ore samples.
Figure 5. Flow chart for processing difficult-to-select lepidolite ore samples.
Minerals 15 00750 g005
Minerals 15 00750 g006
Figure 6. BDB structure chart [82].
Figure 6. BDB structure chart [82].
Minerals 15 00750 g006
Minerals 15 00750 g007
Figure 7. Effect of Fe (III) dosage on lepidolite, feldspar, and quartz.
Figure 7. Effect of Fe (III) dosage on lepidolite, feldspar, and quartz.
Minerals 15 00750 g007
Minerals 15 00750 g008
Figure 8. Mechanism of selective inhibition of feldspar and quartz by Fe (III) [56].
Figure 8. Mechanism of selective inhibition of feldspar and quartz by Fe (III) [56].
Minerals 15 00750 g008
Minerals 15 00750 g009
Figure 9. Zeta potential of lepidolite and associated gangue minerals.
Figure 9. Zeta potential of lepidolite and associated gangue minerals.
Minerals 15 00750 g009
Table 1. World lithium production and its reserves (t).
Table 1. World lithium production and its reserves (t).
Mine Production Reserve
202220232024 (Prediction)
Australia16,00022,40027,0001,500,000
Argentina6400720094002,000,000
Chile15,30018,00022,5007,600,000
China3300630090003,300,000
Zimbabwe20003500520022,000
Brazil55060075047,000
World total43,55062,20073,85014,000,000
Table 2. Polytypes of muscovite and their characteristics [59].
Table 2. Polytypes of muscovite and their characteristics [59].
PolytypeCrystal SystemFrequencySpace Group
2M1MonoclinicCommonC2/c
2M2MonoclinicUncommonC2/c
3TTrigonalRareP3112
Table 3. Basic characteristics and structure of lepidolite and its major gangue minerals.
Table 3. Basic characteristics and structure of lepidolite and its major gangue minerals.
MineralsColorsDensity (g/cm3)Chemical FormulaCrystal Structure
Lepidolite [50]Light white, lavender or purple2.6–3.0K(Li,Al)3(Al,Si)4O10(F,OH)2Monoclinic Crystal
Muscovite [48]Colorless, white or gray2.6–3.0K2Al4(Si6Al2)O20(OH)4Monoclinic crystals
Quartz [68]Colorless or creamy white2.6SiO2Tetragonal Crystal System
Feldspar [66]Colorless or off-white2.6–2.75(Na,K)(Al,Si)4O8Monoclinic Crystal
Table 4. General lepidolite flotation process and characteristics.
Table 4. General lepidolite flotation process and characteristics.
Flotation ProcessesCharacteristics
Acid flotation [74]Lower cost, but serious equipment corrosion, high foam viscosity
Neutral flotation [75]Environmentally friendly, but mud interference, need to rely on dispersants to inhibit sludge
Desliming flotation [78]Simple process, good results, but irreversible loss of fine-grained lepidolite
Selective flocculation flotation [78]Strengthen the sorting efficiency, reduce the loss of desliming, high sensitivity to chemicals, industrialization is difficult
Combined reciprocal flotation [80]Suitable for complex lepidolite system, high comprehensive recovery rate, complex process, industrialization difficulties
Table 5. Typical cationic reagent structures and their characteristics.
Table 5. Typical cationic reagent structures and their characteristics.
Reagent NameMolecular StructureCharacteristics
Primary amine [58]Minerals 15 00750 i001High collectability
Secondary amine [34]Minerals 15 00750 i002Low consumption
Tertiary amine [81]Minerals 15 00750 i003Low sensitivity to slurry
Quaternary ammonium salt [82]Minerals 15 00750 i004Low sensitivity to slurry, good foaming properties
Table 6. Lepidolite depressants and their Mechanisms.
Table 6. Lepidolite depressants and their Mechanisms.
TypeNameDepressing Mechanism
Inorganic depressant [92]Sodium SilicateHydrolyzed to form colloidal silicate polymers, hindering the adsorption of traps.
Sodium hexametaphosphateGeneration of refractory complexes on the surface of chalcopyrite, hindering the adsorption of traps.
Organic Depressants
[98,99]		TanninGeneration of strong hydrophilic film on mineral surface
Oxalic acidGeneration of insoluble metal complexes, enhancing hydrophilicity of minerals
LigninDisperses sludge and acts selectively on gangue minerals
Combined depressant [105]Tartaric acid-starch-keroseneCombines the advantages of various depressants to increase the difference in floatability between lepidolite and chondrites.
Sodium hexametaphosphate-sodium silicate
Sodium Carbonate-Sodium Silicate
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Yang, X.; Feng, B.; Jiang, L. Froth Flotation of Lepidolite—A Review. Minerals 2025, 15, 750. https://doi.org/10.3390/min15070750

AMA Style

Yang X, Feng B, Jiang L. Froth Flotation of Lepidolite—A Review. Minerals. 2025; 15(7):750. https://doi.org/10.3390/min15070750

Chicago/Turabian Style

Yang, Xusheng, Bo Feng, and Longxia Jiang. 2025. "Froth Flotation of Lepidolite—A Review" Minerals 15, no. 7: 750. https://doi.org/10.3390/min15070750

APA Style

Yang, X., Feng, B., & Jiang, L. (2025). Froth Flotation of Lepidolite—A Review. Minerals, 15(7), 750. https://doi.org/10.3390/min15070750

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop