Direct Lithium Extraction from Seawater Brine: An Assessment of Technology and Existing Commercial Systems

Abstract

Traditional lithium extraction methods are time-consuming and energy-intensive, often leaving a large environmental footprint due to significant freshwater consumption. However, direct lithium extraction (DLE) technologies offer a more efficient and sustainable alternative. DLE can reduce the production time and energy consumption of the overall system, leading to lower costs. This technology is especially promising for extracting lithium from low-concentration brine such as seawater, which contains 8000 times more lithium than land sources. With global demand for lithium expected to reach a third of commercially available land-brine reserves by 2050, DLE’s potential to tap into the vast ocean reserves is crucial. Numerous organizations and developers are working to develop and refine new DLE systems to meet the growing demand for lithium, while others are working on integrating various DLE technologies to create more advanced and efficient systems to enhance extraction efficiency, product quality, and cost-effectiveness. In this review, we assess DLE’s commercial potential, providing an overview of the technology and examining current commercially deployed systems.

1. Introduction

Lithium plays a crucial role in various applications, with its primary use in the manufacturing of batteries. The production of batteries, particularly lithium-ion batteries, for electric vehicles (EVs), smartphones, and energy storage systems accounts for the largest share of lithium demand in industrial applications. In 2021, global lithium demand by end-market was estimated to be about 500,000 metric tons of Li, projected to quintuple, reaching 2.5 million metric tons of Li, by 2030. The production of EVs is the primary driver of this demand. According to Bloomberg, global EV sales are expected to grow from 1 million vehicles in 2017 to 25 million by 2030, making EVs the critical force behind the increase in lithium demand, which currently constitutes about 70% of the global market [1,2,3]. Beyond batteries, lithium is essential in numerous other applications: it enhances the properties of metal alloys, lithium oxide is used to produce glass and ceramics, and lithium chloride cools air conditioning and industrial drying systems. Additionally, lithium carbonate is used in medications to treat manic depression, and lithium hydride stores hydrogen for fuel use [4,5].

Lithium is primarily mined from two sources: hard rock deposits and brines. Current brine sources mainly include salar brines. About 30% of global lithium production is located in Chile and Argentina, originating from the salar lakes in the so-called lithium triangle (Figure 1). In addition to the lithium triangle of South America, Australia’s hard rocks also make up a significant 49% of lithium global production [6,7,8,9].

Another existing resource for lithium extraction, brine, is the byproduct of desalination. In arid regions such as the Middle East, Southern Europe, and the U.S. West Coast, desalination technologies are the primary source of freshwater [10,11]. Seawater brine, which contains concentrated ions and chemicals from the desalination process, is particularly rich in lithium compared to regular seawater. This higher concentration of lithium in brine enhances the potential for lithium recovery on a per-volume basis and presents an opportunity to further process the brine before disposal. Utilization of brine could improve the overall economics of desalination projects, making them more attractive to investors. Additionally, with lithium in short supply on land and concentrated in only a few countries, researchers are exploring ways to extract lithium from seawater brine. Oceans collectively hold 8000 times more lithium than is found on land, offering a vast untapped resource [12].

Meeting the growing global demand for lithium presents significant challenges. Companies will likely face production delays as they struggle to secure adequate lithium supplies (Figure 2). As a result, the lithium industry is increasingly turning to more expensive but highly efficient methods of sourcing and processing to increase the production of compounds needed for battery production. Additionally, industries are exploring untapped sources of lithium. Another promising approach is battery recycling, a newly developed technology that keeps lithium in circulation longer and addresses the growing problem of battery waste pollution [13,14]. Moreover, direct lithium extraction (DLE) technologies offer a means to enhance efficiency and reduce overall production costs from existing brine sources. This can potentially be achieved by reducing production time from months to days and hours, reducing land footprint by having more compact systems, and reducing the system’s overall water and chemical consumption by eliminating evaporative ponds and improving the extraction efficiency. The shorter production time and increased efficiency can potentially increase product yield and purity. DLE also opens possibilities for extracting lithium from low-concentration brines, thereby expanding the potential sources of this critical resource [15,16].

As the demands for both lithium and freshwater continue to rise alongside technological advancements, seawater brine presents a promising future source of lithium to help meet global demand. The new technology can potentially turn the source of lithium in the seawater into an available reserve. Given the potentially lucrative economics and the vast availability of lithium in the ocean, our focus is increasingly shifting toward extracting lithium from seawater brine [9,17,18,19].

2. Lithium in Seawater

The rise in seawater desalination plants, driven by increasing freshwater demand, has prompted researchers to explore ways to recover minerals and raw metals from the resulting brine. By 2050, it is estimated that nearly 1/3 of the 14 million tons of the commercially available land lithium reserve will be consumed (Figure 3). Oceans contain approximately 230 billion metric tons of lithium compared to just 28 million metric tons of land-based lithium, according to the 2024 US Geological Survey. A significant portion of commercial lithium is produced through brine extraction, and the main challenge lies in the concentration levels. Lithium in seawater exists at a concentration of only 180 parts per billion (ppb), with a sodium-to-lithium ratio of 60,000:1 (Table 1). In contrast, commercial lithium production typically relies on source brines with lithium concentrations ranging from 300 to 7000 parts per million (ppm). Lithium extraction is affected by ions with similar chemical properties, such as Na, K, Mg, and Ca. Regardless, pretreatment processes, such as NF, can remove Mg and Ca from brine. The sodium-to-lithium ratio affects lithium’s extraction selectivity since sodium is monovalent with the same valence state as lithium and is present at very high concentrations. In commercialized lithium extraction, brines have a sodium-to-lithium ratio ranging from around 700:1 to 3:1. The high ratio of Na⁺/Li⁺ in seawater results in low-purity products or high production costs with the introduction of an extensive purification process. K/Li ratio may also pose a challenge, but at a more manageable level due to the lower concentration of potassium and the smaller ion size of 0.78 Å compared to 1.38 Å of lithium and 1.02 Å of sodium. As a result, while extracting lithium from seawater is technically possible, it is not economically viable with current lithium extraction technologies [12,20,21].

Seawater desalination plants typically use reverse osmosis (RO) technology, which produces a purified permeate stream and a concentrated brine as the reject stream. This rejected brine is usually discharged back into the sea [22,23]. However, recovering lithium and other valuable materials from the RO reject brine is possible. This recovery is generally achieved through a multistep process that involves the sequential application of chemical reactants to adsorb, desorb, and crystallize lithium [12,20,24,25].

Table 1. Minerals and metals concentrations in seawater [24].

Minerals and Metals	Concentration (ppm)	Minerals and Metals	Concentration (ppm)
Chloride	18,980	Sodium	10,561
Magnesium	1272	Sulfur	884
Calcium	400	Potassium	380
Bromine	65	Inorganic Carbon	28
Strontium	13	Boron	4.6
Silicon	4	Organic Carbon	3
Aluminum	1.9	Fluorine	1.4
Nitrate	0.7	Organic Nitrogen	0.2
Rubidium	0.2	Lithium	0.18
Phosphorous	0.1	Copper	0.09
Barium	0.05	Iodine	0.05
Nitrite	0.05	Ammonia	0.05
Arsenic	0.024	Iron	0.02
Organic Phosphorous	0.016	Zinc	0.014
Manganese	0.01	Lead	0.005
Selenium	0.004	Tin	0.003
Cesium	0.002	Molybdenum	0.002
Uranium	0.0016	Gallium	0.0005
Nickel	0.0005	Thorium	0.0005
Cerium	0.0004	Vanadium	0.0003
Lanthanum	0.0003	Yttrium	0.0003
Mercury	0.0003	Silver	0.0003
Bismuth	0.0002	Cobalt	0.0001
Gold	0.000008

Table 1. Minerals and metals concentrations in seawater [24].

Minerals and Metals	Concentration (ppm)	Minerals and Metals	Concentration (ppm)
Chloride	18,980	Sodium	10,561
Magnesium	1272	Sulfur	884
Calcium	400	Potassium	380
Bromine	65	Inorganic Carbon	28
Strontium	13	Boron	4.6
Silicon	4	Organic Carbon	3
Aluminum	1.9	Fluorine	1.4
Nitrate	0.7	Organic Nitrogen	0.2
Rubidium	0.2	Lithium	0.18
Phosphorous	0.1	Copper	0.09
Barium	0.05	Iodine	0.05
Nitrite	0.05	Ammonia	0.05
Arsenic	0.024	Iron	0.02
Organic Phosphorous	0.016	Zinc	0.014
Manganese	0.01	Lead	0.005
Selenium	0.004	Tin	0.003
Cesium	0.002	Molybdenum	0.002
Uranium	0.0016	Gallium	0.0005
Nickel	0.0005	Thorium	0.0005
Cerium	0.0004	Vanadium	0.0003
Lanthanum	0.0003	Yttrium	0.0003
Mercury	0.0003	Silver	0.0003
Bismuth	0.0002	Cobalt	0.0001
Gold	0.000008

3. Products and Market

The market for lithium-based products has seen significant changes over the years. In 2000, lithium carbonate and lithium hydroxide accounted for 65% of the market share. By 2020, lithium carbonate had grown to represent 50% of the market, while lithium hydroxide increased to 30%, comprising 80% of the market share.

Table 2. Forecast of lithium end-products market percentages and prices [27,28,29,30,31,32,33,34,35,36,37,38,39,40].

Year	Lithium Carbonate (%)	Lithium Carbonate Cost (USD/ton)	Lithium Hydroxide (%)	Lithium Hydroxide Cost (USD/ton)	Lithium Chloride (%)	Lithium Chloride Cost (USD/ton)	Lithium Bromide (%)	Lithium Bromide Cost (USD/ton)	Lithium Sulfate (%)	Lithium Sulfate Cost (USD/ton)	Lithium Nitrate (%)	Lithium Nitrate Cost (USD/ton)
2000	40%	6000	25%	7000	25%	5500	5%	4500	3%	4000	2%	3800
2005	42%	6500	26%	7500	22%	5800	5%	4700	3%	4200	2%	4000
2010	45%	7000	30%	8000	20%	6000	5%	5000	3%	4500	2%	4200
2015	50%	8000	27%	9000	18%	6500	5%	5500	3%	4800	2%	4500
2020	50%	9000	30%	11,200	15%	7000	5%	5800	3%	5000	2%	4800
2025	48%	10,000	32%	12,500	14%	7500	4%	6000	2%	5200	2%	5000

and Figure 4 show the changes in the percentage of lithium-end products in the market and their costs. These two compounds are primarily used in secondary batteries, greases, and aluminum alloys, whereas mineral concentrates serve as raw materials in ceramics and glass production. In 2007, the ceramics and glass industries were the largest consumers of lithium products, holding 37% of the market share compared to 20% for batteries. However, the surge in electric vehicle (EV) production has led to a sharp increase in demand for lithium carbonate and lithium hydroxide [7,26].

Lithium carbonate is the most common end-product of both brine and mineral-based lithium extraction technologies. This compound has various industrial applications, including battery manufacturing and producing flooring treatments, cement densifiers, adhesives, and glazes. Other frequently used lithium products include lithium hydroxide, commonly used in making lithium salts; lithium chloride, primarily used to produce lithium metal; and lithium bromide, a desiccant in air-conditioning systems. Additionally, butyllithium is extensively used as a strong base in organic chemistry, while pure lithium metal is employed in rechargeable batteries for devices like phones and laptops. Lithium hydroxide is increasingly becoming the preferred choice for electric vehicle manufacturers as it facilitates the production of higher-performing, longer-lasting batteries [7,26].

In 2021, batteries, ceramics, and glass accounted for 88% of global lithium end uses, with batteries alone comprising 74% (Figure 5). Lithium’s role in ceramics and glass, which comprised 14% of usage, is crucial for enhancing durability, corrosion, and thermal resistance. By 2022, batteries were expected to account for 80% of total demand, while ceramics and glass were projected to represent 7% [7,26,41].

Due to soaring demand, lithium carbonate prices have been highly volatile over the past decade. Prices surged from $7000 per ton in January 2021 to $26,200 per ton by November 2021, eventually reaching $67,000 per ton by November 2022. Supply constraints and the growing demand for electric vehicles have driven this sharp increase. Similarly, lithium hydroxide prices rose significantly, climbing from $35,300 per ton in January 2022 to $78,000 per ton by November 2022 [41]. From 2023 to 2024, a decline in EV sales was accompanied by a decrease in the average prices of lithium carbonate. Nevertheless, the average prices of lithium-based products overall continue to rise, as shown in Figure 4B.

4. Lithium Extraction Technologies

Lithium extraction methods can differ depending on the source of lithium. In traditional brine operations, lithium-rich brine is pumped to the surface and concentrated through evaporation in a series of artificial ponds for 12 to 18 months. During this process, salts like sodium chloride and potassium chloride precipitate and are removed while the lithium concentration increases. Afterward, the brine undergoes chemical treatment and filtration to eliminate impurities. The resultant concentrated lithium solution is then transformed into technical-grade lithium carbonate using soda ash. However, emerging technologies are being developed to enhance extraction and minimize chemical use. Innovations like direct lithium extraction (DLE) and battery recycling are emerging as alternatives to traditional methods [42]. An overview of the different categories of lithium extraction is shown in Figure 6.

4.1. Traditional Lithium Extraction from Brines

In a conventional lithium extraction, brine-containing lithium is first concentrated to a level suitable for adequate recovery. The brine is pumped into an evaporation pond where solar energy evaporates water and increases the concentration of Li+ in the brine. Once the lithium chloride (LiCl) concentration in the pond reaches approximately 6000 ppm, the brine is transferred to a recovery pond. Depending on the brine composition and environmental conditions, evaporation may occur in multiple stages, during which other salts such as sodium (Na), magnesium (Mg), and potassium (K) are also harvested. Calcium hydroxide (Ca(OH)₂) is added to precipitate magnesium as magnesium hydroxide (Mg(OH)₂) and to remove sulfate as calcium sulfate (CaSO₄) through single-replacement and acid-base neutralization reactions, respectively. The remaining brine is then treated with sodium carbonate (Na₂CO₃) to precipitate calcium as calcium carbonate (CaCO₃) via a single-replacement reaction. As Na₂CO₃ is introduced, the brine becomes critically supersaturated, initiating the crystallization of lithium carbonate (Li₂CO₃). The end product is a chemically stable, odorless, white powder. Typically, this initial lithium carbonate product is dissolved and re-precipitated multiple times to achieve battery-grade purity (99.5 wt%) [43].

This lithium extraction method is the most conventional and cost-effective because it uses solar energy to concentrate lithium ions (Li⁺). The process also benefits from relatively low initial investment requirements, thanks to inexpensive chemicals for ion salt precipitation and the simple production infrastructure. However, despite these initial cost advantages, the economic viability of traditional lithium extraction from low-concentration aqueous solutions depends on four critical factors: (1) the suitability of land and climate; (2) the production life cycle duration; (3) the natural concentration of lithium in the brine; and (4) the mass ratio of competing ions relative to lithium.

This evaporative extraction method is time-consuming and unsuitable for all geographical locations due to significant climate variations. Its efficiency is highly contingent on the brine composition, which can differ widely across locations. The presence of other ions at high concentrations can lead to co-precipitation, complicating the lithium recovery process. For example, magnesium ions (Mg²⁺) have a chemistry similar to lithium ions (Li⁺). They may co-precipitate as magnesium carbonate and lithium carbonate, making the subsequent recovery of lithium salts more challenging.

More importantly, evaporative technologies accompanied by severe water loss might also lead to water scarcity in the surrounding areas, as observed in Chile [44,45]. Based on these shortcomings of the evaporative methods, researchers have been focusing on ‘non-evaporative’ technologies for brine concentration, which are discussed in the following sections.

4.2. Direct Lithium Extraction

DLE encompasses technologies that enable lithium extraction from brine without relying on the extensive time and space required by traditional evaporation ponds. Unlike conventional methods, which can take 12 to 18 months with multi-stage operations, DLE can extract lithium in a single-stage process with the addition of post and pre-treatments, which can be completed within hours or days. In addition, DLE offers more compact solutions, significantly reducing the massive land footprint of traditional extraction methods. Some DLE technologies have the potential to significantly reduce water consumption by eliminating the evaporation pond and reducing the environmental impact caused by the ponds, thereby lowering the cost of lithium production. Regardless of its many significant advantages, DLE comes with its challenges. DLE is still evolving, and its scalability for industrial applications is still challenging for some of its technologies.

Table 3. DLE and traditional lithium extraction comparison.

	Direct Lithium Extraction	Traditional Lithium Extraction
Process duration	Hours to days, which can be done in a single-stage operation	12 to 18 months, which requires a multi-stage operation
Land footprint	Compact operation allows for a larger scale with a small footprint.	Massive footprint due to the need for large open areas that are suitable for pond evaporation
Geographical dependent	Weather-dependent and less land-dependent due to its small footprint	Heavily reliant on weather and land suitability
Water consumption	DLE elimination of evaporative ponds significantly reduces water consumption	Massive water consumption and large amounts of water lost during the evaporation process
Energy consumption	DLE tends to have higher energy consumption. However, the introduction of renewable energy sources within the plant can help reduce both energy costs and environmental impact. DLE also reduces the intensity and requirement of the post-treatment and purification processes, making it potentially less energy-intensive	Low energy consumption is primarily attributed to the use of solar power for brine evaporation. Nevertheless, if post-treatment and purification processes are included, the energy consumption would increase significantly
Environmental impact	Smaller ecological footprint due to compact size, utilization of more efficient lithium-selective techniques, and reduction in water and chemical usage. Additionally, the selectivity of lithium and low chemical usage means that natural brine can be recycled back to its reservoir after lithium extraction, preventing the destruction of the existing ecosystem	Pond evaporation results in soil degradation, water pollution, and consumption of high natural brines, leading to habitat and biodiversity destruction
Carbon intensity	Consuming less energy per product, using efficient techniques, and implementing renewable, clean energy will reduce energy consumption and greenhouse gas emissions. In addition, increasing lithium production aids the speed of transaction to clean renewable energy sources	The pond evaporation process requires low energy. However, its low efficiency requires energy-intensive post-treatment to meet market demand
Cost-effectiveness	Efficient and selective extraction reduces process duration, water consumption, and purification processes, offering long-term cost advantages. However, the initial investment costs for implementing it can be high. Additionally, DLE has higher energy consumption. Nevertheless, DLE is still evolving, and its evaluation at a larger industrial scale remains uncertain	Longer process duration and high water consumption contribute to higher costs. In addition, the lower process efficiency leads to the need for extensive purification and pretreatment steps, increasing chemical consumption. Regardless, traditional extraction exhibits low energy consumption
Complexity and scalability	DLE processes tend to be more complex and compact than traditional methods. This may offer many advantages, but it also has its challenges. These challenges include safety and maintenance concerns and scalability issues. Most DLE technologies are still in their initial stages, and their scalability to meet industrial production demands remains to be proven	Less complexity than DLE means lower maintenance and safety concerns. It is also scalable and has been used for years in industrial lithium production
Product purity	DLE’s high efficiency and selectivity of lithium lead to higher product purity and lithium recovery	Low efficiency and selectivity of the process means that extensive purification processes are needed to meet the market requirements
Resource availability	The availability of suitable adsorbents, resins, or membranes limits the widespread adoption of DLE methods	The long-standing industrial establishment of traditional methods means finding resources and equipment is much easier and cheaper

shows DLE’s advantages and challenges compared to conventional methods.

Despite DLE’s advantages, it has not yet become the state-of-the-art technology, primarily due to limitations in scalability and proven large-scale performance compared to established methods like evaporation ponds. Furthermore, the effectiveness of different DLE technologies varies significantly depending on the specific chemical composition of the lithium-rich brine, and many DLE methods are still in the process of technological maturation and optimization. The significant upfront capital investment required for DLE implementation, along with potential environmental concerns associated with specific DLE processes and the inherent risk aversion within the mining industry, also contribute to the continued prevalence of traditional extraction techniques. DLE methods are categorized into five primary types: adsorption, ion exchange, solvent extraction, membrane processes, and electrochemical techniques. Figure 7 and

Table 4. Advantages and disadvantages of DLE technologies [6,46,47,48,49,50].

DLE Technologies	Advantages	Disadvantages	Seawater Brine Readiness
Adsorption (TRL: 7–9)	Sorbent regeneration is usually performed with water and not acid, resulting in longer sorbent lifetimes Most established DLE technology Simple process design Low energy usage Low footprint and environmental impact Short process time Adaptable High selectivity	Relatively low sorbent capacities, resulting in lower LiCl concentrations in the eluate Usually requires temperatures above 40 °C. High water consumption The exchange of end-of-life sorbent can cause significant downtime. Often requires an additional concentration step after the extraction Time-consuming compared to other DLE Complex regeneration of adsorption	Not ready as it requires a higher lithium concentration to be economically viable
Ion Exchange (TRL: 7–9)	High sorbent capacities, facilitating high LiCl concentrations in the eluate High selectivity for lithium leads to high purity levels and minimal contamination. High lithium concentration in the strip solution Simple process design Low initial investment Relatively low energy usage	Large amounts of acid/base are required, which can result in high OPEX and CAPEX Use of hazardous chemicals Sorbent degradation is possible due to repeated exposure to acid The exchange of end-of-life sorbent can cause significant downtime An additional concentration step may be required after the extraction Sorbent costs can be high Weak lithium-uptake capacity	Not ready as it requires a higher lithium concentration to be economically viable
Solvent Extraction (TRL: 7–8)	High concentration of lithium in the stripping solution (no additional concentration step required) Continuous process (high throughput) Can have a high selectivity for lithium (Li+) versus sodium (Na+) and magnesium (Mg2+) Low capital investment Relatively simple equipment	Higher cost relative to other DLE technologies Brine may require post-treatment after the DLE step due to solvent residues Use of organic solvents (environmental risks, health risks, fire risks with high-temperature brines, etc.) Corrosion of equipment High waste production Use of hazardous materials	Not ready, but it has the highest readiness of all DLE (depending on the solvent)
(Electro-)Membrane Separation (TRL: 4–8)	High lithium selectivity High lithium concentrations in the eluate Novel electrodialysis technologies have low energy requirements No chemicals are used Can be continuous (high throughput) No contact between the extractant and brine Simple process No need for additional purification	In some instances, limited to brines with low magnesium (Mg2+), calcium (Ca2+), sodium (Na+), or potassium (K+) concentrations due to membrane fouling/scaling Pre-treatment may be required It can be energy intensive Often water-intensive Membranes can be expensive In some instances, it is not suitable for directly treating high-temperature brines (e.g., geothermal brines) High initial and operation costs	The CDI membrane shows great promise for the future but is not yet ready. NF also shows potential, primarily as pre-treatment for removing multivalent ions. ED systems are also promising. All membrane technologies, except for NF for pre-treatment purposes, are not yet ready for use with low-concentration lithium brines
Electrochemical Separation (TRL: 3–8)	Low energy consumption Low water consumption High selectivity No chemicals are used Environmentally friendly	Fouling potential A high amount of electrolytes is required The long-term stability of electrodes has not yet been thoroughly evaluated for brines	This category shows the most futuristic potential, especially EIPS and CDI. Nevertheless, it is not yet ready

provide a brief overview of each category [6,42,46,47,48].

4.2.1. Adsorption

The most mature direct lithium extraction (DLE) technology is adsorption. Most adsorption systems are in the pre-commercial to commercial stage (TRL 7–9). This method is particularly effective for seawater brine due to its high lithium selectivity. The product of the adsorption process can vary depending on the feed and process used, with lithium chloride (LiCl) being the most common product. In this process, lithium is adsorbed onto a lithium-selective solid sorbent as the brine passes through it. The lithium is then desorbed using a regeneration solution, typically warm water. A key advantage of adsorption is that it requires less brine pre-treatment than solvent extraction methods. It also achieves over 90% lithium recovery, operates faster, and occupies a smaller footprint than traditional methods. Additionally, the absence of acid in the regeneration process gives adsorption an advantage over ion exchange technologies, resulting in lower costs and a longer lifespan for the sorbent materials [6,42,48].

• Aluminum-Based Adsorbents (LiAl-LDHs)

Aluminum-based adsorbents are widely utilized in direct lithium extraction (DLE), with lithium-aluminum layered double hydroxides (LiAl-LDHs) being particularly prevalent in commercial applications. These adsorbents feature a disordered layered structure with a general chemical formula of LiX·2Al(OH)₃·nH₂O, where X represents anions, commonly chloride (Cl), and n denotes the number of water molecules. LiAl-LDHs exhibit a plate-like arrangement of aluminum hydroxide layers linked through hydrogen bonds, electrostatic interactions, and van der Waals forces. These interactions facilitate the efficient adsorption of lithium into the octahedral vacancies within the structure. Lithium’s specific affinity for this process is attributed to its ability to penetrate the Al(OH)₃ framework and occupy the octahedral sites. At the same time, larger alkaline earth metal ions cannot effectively do so due to steric hindrance. Despite the ionic radius of magnesium (Mg²⁺) being similar to that of lithium (Li⁺), with Mg²⁺ measuring 72 pm and Li⁺ 76 pm, magnesium forms complex ions with water ([Mg(H₂O)₆]²⁺) that significantly increase its effective ionic radius to 428 pm, hindering its adsorption. The following equation illustrates the process for lithium chloride extraction using LiX·2Al(OH)₃·nH₂O-based adsorbents.

xLiCl + (1 − x)LiCl⋅2Al(OH)₃⋅(n + 1)H₂O → LiCl⋅2Al(OH)₃⋅nH₂O + H₂

Initially, doping Al³⁺ and replacing Mn³⁺ with it, due to its comparable size and superior chemical stability, was a method employed for enhancing lithium extraction capabilities. Li/Al double hydroxide is also recognized as an effective adsorbent for lithium recovery, with an adsorption capacity of approximately 7–8 mg/g. Studies have demonstrated that a higher Mg/Li ratio can improve lithium extraction, as the presence of Mg²⁺ significantly enhances the adsorption capacity for Li⁺. Although these adsorbents typically have lower capacity, they offer advantages such as lower production costs, straightforward fabrication, and ease of regeneration [6,42].

• Commercial Technologies

Adsorption DLE has been the fastest-growing DLE technology field. As new systems and projects are developed, this branch of DLE is becoming the most dominant and favorable. Companies that have developed or are developing absorption-based DLE systems or projects are growing rapidly, with more systems currently available. Companies with industrial systems include Livent, Lithium Harvest, Sunresin, and Sorcia Minerals, with more companies joining, such as Eramet, International Battery Metals, Koch, and Summit Nanotech. Combining different DLE absorption systems and projects from various companies, the following showcases a brief description from the most developed to the least. For more information on each company, refer to Supplement S1.

Livent, a global leader in lithium technology, has developed the ILiAD DLE technology. This innovative solution significantly reduces the physical footprint of lithium extraction, making it ten times smaller than hard rock methods and 1000 times smaller than conventional salar. More importantly, it contributes to the conservation of freshwater and is compatible with almost all brine resources, demonstrating a lifespan of up to 6 years. The ILiAD system operates without chemical reagents, using water for a liquid stripping procedure that minimizes damage and extends the system’s lifespan. Livent provides a fully assembled modularized system, and the technology is already in commercial use at Salar del Hombre Muerto, Argentina [51,52].

Lithium Harvest (LH) technology is a game-changer in the industry, extracting lithium and critical minerals from produced water. This approach not only reduces environmental impact but also maximizes resource efficiency. It eliminates the need for large-scale evaporation ponds or disruptive mining operations, offering faster extraction rates, reduced water consumption, and a unique mobile and modular system. The technology’s low energy and freshwater consumption, with 96% less water consumption, 70% lower CAPEX, and 35% lower OPEX make it a promising solution. It also recycles 90% of consumed water for secondary reuse and achieves a lithium recovery of >95%. The project implementation time is between 12 and 15 months, making it a swift and efficient solution [6,53].

Sunresin, a major DLE lithium sorbent producer in China, offers comprehensive EPC solutions for lithium production. By 2022, they had taken on nine commercial DLE projects with a total capacity of 73,000 tons of lithium carbonate and lithium hydroxide. Their technology, known for its shallow sorbent loss, quick production capacity, and competitive costing, is a testament to Sunresin’s commitment to cost-effectiveness. The Sunresin SMB system reduces sorbent quantity, cost, and footprint while removing Ca, Mg, and boron. Additionally, their unique Li/Na separation in the adsorption resin unit can increase plant yield by 10%, further enhancing the technology’s financial viability [54].

Sorcia Minerals has developed a unique lithium extraction technology that reduces carbon emissions, eliminates evaporation ponds, and decreases lithium chloride production cycle time. The process also minimizes construction and start-up time, with low operating costs and a modular plant design that can be installed at brine resources in under one year. This innovative technology boasts an improved lithium extraction efficiency of 75%–90%, compared to 30%–40% for traditional evaporation ponds [55].

Eramet specializes in designing, constructing, and operating mining procedures for the mining industry. They focus on producing critical metals for energy transactions to renewables, such as lithium, cobalt, and nickel. Eramet’s lithium production projects are divided into three sectors: battery recycling, salar brine, and geothermal brine. The BofA Lithium (DLE) project is an Eramet salar brine project in Salta, Argentina. It has a 40-year life of mine with estimated resources of 10 million tons of LCE. The Eramet DLE technology, based on aluminum-based lithium sorbent, provides 90% lithium recovery at the DLE unit and operates at the native temperature of the brine [56,57]. International Battery Metals (IBAT) has developed a breakthrough technology for lithium production called direct lithium extraction (DLE). The technology boasts a high-quality % recovery rate of 95% and is set to commission its first commercial plant in the second quarter of 2024. The environmentally friendly system uses minimal chemicals and generates minimal waste by products. It comprises six main steps, including pretreatment, the DLE process, and concentration using reverse osmosis and multistage evaporation processes. The overall recovery of lithium chloride is 95% [13,58].

Koch Separation Solutions (KSS) developed the Li-PRO™ process for direct lithium extraction (DLE), increasing lithium recovery and yielding higher-purity products. The process offers improved performance, reduced processing time, lower capital costs, and a smaller equipment footprint. It comprises pretreatment, DLE, softening, and concentration stages. The system uses advanced technologies such as ultrafiltration, lithium selective sorption, ion exchange softening, and RO concentration to remove impurities and excess water, yielding high-purity lithium chloride. KOCH offers standard and customized piloting options to accommodate various capacities [59,60].

Summit Nanotech’s patented technology extracts lithium from salar brines, shortening production time from 18 months to 1 day. The process also reduces the land footprint by 96% and achieves over 90% lithium recovery. The system efficiently treats raw brine to produce lithium carbonate for use in electric vehicle batteries. The project’s pilot program in Chile aims to accelerate the lithium supply for electric vehicles while conserving freshwater and preserving land [61].

The ATLiS project by EnergySource Minerals is a leading lithium extraction project in development in California. It aims to create a low-impact DLE system on just 40 acres of land, using minimal water and producing low carbon emissions. The project employs Livent’s ILiAD technology for lithium extraction from geothermal brines through a four-stage process [62].

Watercycle Technologies Ltd. is a UK-based company that develops sustainable mineral extraction and water treatment systems. Their DLEC Process focuses on extracting lithium from the brine using DLE technologies and renewable energy sources. The process consists of three main stages: DLE adsorption, MD membrane technology, and crystallization. The company is currently piloting the DLEC process and conducting further tests [63].

Vulcan’s Zero Carbon Lithium™ Project aims to revolutionize lithium production by developing a dual lithium chemicals and renewable energy business with zero greenhouse gas emissions. The project uses advanced adsorption DLE technology, constituting 10% of lithium production today, and is set to increase to 15% market share in the next ten years. This technology has high lithium selectivity (>90% extraction efficiency) and uses water for lithium stripping instead of acid, resulting in a longer sorbent lifespan. Vulcan uses geothermal brine for its process, reducing energy usage. The project aims to introduce renewable energy sources to further its environmental impact benefits. Vulcan has completed the in-house design for the Lithium Extraction Optimization Plant (LEOP) and is set to start commercial production in late 2025 [64].

ExSorbtion has acquired and is commercializing the technology developed by SRI International. This technology involves patented sorbents with high lithium selectivity and fast reaction time for adsorbing lithium from the brine. The patented regeneration process uses carbon dioxide gas to extract the adsorbed lithium from the sorbents, extending their lifespan by over 10%. The technology allows for low operating costs and high lithium selectivity, suitable for low-grade brines. The process has fast kinetics and significantly lower water consumption than other methods, requiring 23 tons of water for each ton of lithium carbonate [65].

Eon Minerals is a leading technology company that develops new materials for a sustainable future. EON Lithium Corporation is developing a hybrid process in lithium production, combining direct lithium extraction technology with advanced evaporation techniques. The company owns a test facility and laboratory in Salta, Argentina, and works on the Amanecer lithium project in Pocitos Salar, Argentina. The project aims to produce lithium carbonate using Eon’s patent-pending hybrid direct lithium extraction absorbent technology [66,67].

Warren Buffett’s Berkshire Hathaway Inc. is developing a plan to extract lithium from the superhot geothermal brines beneath California’s Salton Sea. BHE Renewables is leading research on lithium production in California’s Imperial Valley. They aim to recover battery-grade lithium carbonate and plan to operate a commercial plant by 2024. BHE Renewables has received a $14.9 million grant from the U.S. Department of Energy for a demonstration plant to produce battery-grade lithium from geothermal brine [68,69,70].

Rio Tinto and Ford Motor Company have signed a non-binding global memorandum of understanding to develop sustainable supply chains for battery and low-carbon materials used in Ford vehicles. The partnership will supply Ford with lithium, low-carbon aluminum, and copper for a net-zero future. The Rincon Lithium Project in Argentina aims to produce battery-grade lithium carbonate, with a planned annual capacity of 3000 tons by the end of 2024. The project is in its second stage, with a 2000 tpa lithium carbonate operation constructed and in the ramp-up phase [71,72].

TerraLithium provides solutions to extract ultra-pure lithium from geothermal and other brines using proprietary technology. The process integrates into existing geothermal plants and yields minimal environmental impact. It also produces high-purity lithium for extended battery life. The technology is replicable and can be applied to any brine containing lithium. The process has five main stages: brine pretreatment, lithium extraction, brine concentration, electrolysis, and the conversion of LiCl into valuable products like Li₂CO₃, LiOH, and HCl [73].

EnergyX specializes in lithium extraction processes and sustainable solutions for battery-grade lithium products. Their LiTAS™ suite offers selective lithium processing mechanisms, with a 90% lithium recovery rate and a processing time of 1–2 days. The technology, which includes membranes, solvent extraction, and adsorption processes, has low water and power consumption and a cost estimated to be less than $100/ton. The LiTAS technology is set to undergo three phases, including membrane scale-up, testing, and piloting, within a commercial demonstration plant from 2019 to the last quarter of 2024 [74].

Precision Periodic, supported by a grant from the US Department of Energy, is developing a new filtration technology for lithium refining. The technology aims to achieve less than 1% lithium loss, produce high-purity lithium quickly, and minimize environmental impact. The Nano Beads™ used in the process requires no heat or pressure, can be reused, and have a high surface area. The technology efficiently extracts targeted elements with minimal system sizing or flow limitations. The operating pH range is 0 to 8, and the Nano Beads filter media causes low-pressure loss. Testing is ongoing at a pilot plant [75].

Olokun Minerals aims to capture brine waste before it enters the ocean and mine minerals for critical supply chains. The company is developing zSMB technology, which separates lithium chloride from brine using water as the eluent. This environmentally friendly technology also has the potential to extract other minerals simultaneously. Olokun Minerals is working towards achieving over 99% purity and over 90% yield with this technology by the second half of 2024 [76,77].

4.2.2. Ion Exchange

Ion Exchange is a well-established method for Direct Lithium Extraction (DLE), with its technology typically classified at pre-commercial to commercial stages (TRL 7–9). However, most systems are still in the pre-commercial phase. In this process, lithium ions (Li⁺) from brine are chemically bound to a solid ion exchange sorbent. This sorbent functions as a filter for lithium due to its precise porosity, which allows for the selective uptake of lithium ions. Subsequently, the lithium ions are exchanged with other positively charged ions from a stripping solution, commonly hydrogen ions (H⁺) [6,47].

• Manganese-based adsorbents (LMOs)

Manganese-based adsorbents are a type of ion sieve used for lithium extraction. Lithium ions are first incorporated into a manganese compound to create a spinel structure through heat treatment. Subsequently, lithium ions are extracted from this spinel structure using an acid treatment, where protons replace the Li⁺ ions, resulting in a lithium-ion sieve that retains the original crystal structure. This ion sieve can selectively target and retain lithium ions amidst a mixture of multiple ions, a phenomenon known as the ion sieve effect [6].

Studies have demonstrated that increasing the Mg/Mn ratio enhances the adsorption capacity for Li⁺ and the chemical stability of the ion sieve. Adsorption equilibrium is typically achieved within 24 h, with a 23–25 mg/g capacity. Commonly used manganese-based oxides (LMOs) for this purpose include LiMn₂O₄, Li_1.6Mn_1.6O₄, Li₄Mn₅O₁₂, and λ-MnO₂. The equations below illustrate the lithium extraction and regeneration processes for λ-MnO₂-based ion exchangers.

8λMnO₂ + 4Li⁺ + 6H₂O → 4LiMn₂O₄ + O₂ + 4H₃O⁺

2LiMn₂O₄ +2H₃O⁺ → 4λMnO₂ + H₂ + 2H₂O + 2Li⁺

Previous studies have indicated that Li_1.6Mn_1.6O₄ can achieve an adsorption capacity of 40 mg/g within three days, with a recovery rate of 80%. Moreover, similar performance can be obtained in a shorter time frame (1 day) by incorporating sodium bicarbonate and HCl into seawater brine. However, this adsorbent exhibits relatively poor chemical stability [6].

• Titanium-Based Adsorbents

Compared to LMOs, research on titanium-based ion sieves has been less extensive, with most studies focusing on layered Li₂TiO₃ and spinel Li₄Ti₅O₁₂. Studies have shown that Li₂TiO₃ in salt lake brine typically achieves adsorption equilibrium within one day, with a Li⁺ adsorption capacity of 32.6 mg/g at a pH of 6.5. In contrast, Li₄Ti₅O₁₂ has demonstrated a higher Li⁺ adsorption capacity of 38.18 mg/g. Despite these promising results, further research is needed to advance these materials to the pilot stage [6].

Titania-based adsorbents excel in withstanding harsh chemical conditions. H₂TiO₃, for example, demonstrates high selectivity for lithium ions with an adsorption capacity of 25.34 mg/g. Additionally, incorporating a fibrous structure into titanium-based lithium-ion sieves helps prevent aggregation and enhances the adsorption capacity to 59.1 mg/g [6]. Figure 8 summarizes the adsorption capacity of different adsorbents.

• Commercial Technologies

Ion exchange is a well-established branch of DLE. The field has the advantage of having the most research and developments. The branch has variance companies with highly developed systems in their final stages, such as Lilac, Chemionex, GeoLith, Standard Lithium, Volt, and E3 Lithium. In addition, many companies are joining the industry, including Conductive, XtraLit, and Geo40.

Lilac offers a full-service approach to lithium extraction, including subsurface and end-to-end flowsheet support. They have developed a new high-performance ion exchange (IEX) technology to extract lithium from brines. It has ultra-low freshwater usage and achieves high recoveries with all types of brines. The technology has a 10-acre footprint with up to 99% lithium recovery, and the beads used in the process are loaded into vessels that absorb lithium out of the brine. Dilute acid is then used to flush out the lithium, yielding an intermediate of either lithium chloride or lithium sulfate. The technology has successfully extracted lithium from over 80 brines globally, including three field pilot/demo plants [89].

Chemionex is a contract process development and R&D laboratory that offers consulting, R&D, process design, custom pilot plants, chemical analysis, technology assessment, and market studies for various applications. Their services facilitate the removal of trace metallic contaminants from wastewater, high-purity water production, concentration of recovered chemicals, purification of chemicals, and removal of dissolved organic matter, leading to improved product quality and reduced environmental impact. Chemionex utilizes technologies such as ion exchange, adsorption, membranes, electrodialysis, electrolysis, evaporation, and crystallization to enhance its value proposition. The company has two promising lithium-related projects focusing on recovering low lithium levels from concentrated brine and removing divalent metal impurities from concentrated lithium salt solution [90].

GeoLith was established as a research and development company for lithium extraction technologies. Their technology, Li-Capt, uses ion exchange to capture lithium ions in a specially designed material. The technology has undergone three phases of development, from research to industrialization. It aims to eliminate carbon emissions and waste while reducing operational costs. The project is expected to reach full industrial capability in 2024. Li-Capt has been successfully demonstrated in multiple industrial plants and is designed to be adaptable to any brine and extraction project [91].

Standard Lithium (SLI) is a leading company in North America for lithium production. The company has two flagship projects in Arkansas and a third in California. The Phase 1A Project is expected to start production in 2026, while the South West Arkansas Project is set to begin production by 2027. SLI uses Koch Engineered Solutions LiPRO™ LSS technology, showing impressive lithium recovery rates and contaminant rejection levels [92].

Volt is a company using proprietary DLE technology to extract lithium from oilfield brines in North America. The process has three steps: brine treatment, DLE technology extraction, and lithium carbonate concentration. Their demonstration plant achieves 98% lithium extraction rates and can test oilfield brines from various locations. The pilot project is located in Rainbow Lake, Alberta, Canada [93].

E3 Lithium is an Alberta company developing lithium resources using a technology that efficiently extracts lithium from brines. Their DLE ion exchange technology has shown over 90% lithium recovery and 98% impurity removal with low energy consumption. In 2023, a field pilot plant tested their technology, achieving 94% lithium recovery and a high lithium grade in the product stream [94].

Conductive’s technology extracts, concentrates, and refines lithium into battery-grade products. The process involves proprietary ion-exchange materials for lithium extraction from brine and an electrolytic refining process. Conductive has set up multiple pilots in the U.S. and Canada to deploy extraction and refining technology [95].

XtraLit is a lithium technology and resource company that has developed innovative, economically efficient, and ecologically friendly technology for direct lithium extraction (DLE) from brines with low and medium lithium concentrations (5–300 ppm). The XL-DLE technology offers benefits such as boosting lithium supply, reducing pollution and CO₂ emissions, achieving up to 95% lithium recovery, streamlining lead time from exploration to production, and cutting operational and capital expenses. XtraLit targets lithium brine assets with low to medium lithium concentrations, and its technology works in a wide pH range from 3 to 12 with very high selectivity and capacity [96].

Geo40 has developed technology to recover strategic minerals from geothermal brines, including lithium. The process, called sustainable direct lithium recovery, involves six steps. These steps include using Geo40’s proprietary GeoSieve compound to concentrate lithium-bearing geothermal fluid, dewatering the GeoSieve, separating lithium from the GeoSieve, and recycling the GeoSieve for reuse. Geo40 has successfully recovered lithium from various brine types and plans to deploy a larger Demonstration Plant scale by 2024 [97]. Refer to the Supplemental Information Section S1 for more information on each company.

4.2.3. Solvent Extraction

Solvent extraction presents a viable alternative for lithium recovery due to its low cost and high product yield. This method involves using organic solvents that dissolve substantial amounts of LiCl while selectively excluding unwanted salts. Unlike adsorption and ion exchange DLE methods, which rely on solid sorbents, solvent extraction employs a liquid solvent for the extraction process. Lithium ions (Li⁺) or lithium chloride (LiCl) are transferred from the brine into an organic solution, typically composed of kerosene and an extractant. Lithium is subsequently recovered from the organic solution using water. Most solvent extraction systems are currently at the pre-commercial stage (TRL 7–8) [6,48].

Various solvents are employed for lithium extraction, each suited to different Li⁺/Na⁺ ratios and extraction capabilities (Figure 9). Commonly used solvents include tributyl phosphate (TBP), tri-octyl-phosphine oxide (TOPO), dibenzoyl-methane (DBM), LIX 51, and LIX 54. The lithium extraction capacity can vary based on the chosen solvent and the Li⁺/Na⁺ ratio. In TBP-based systems, iron chloride (FeCl₃) facilitates the co-extraction of lithium by first extracting iron, which is a prerequisite for lithium extraction. In this process, Li⁺ combines with [FeCl₄]⁻ to form a complex molecule within the organic solvent. Recovering lithium from this complex requires high acid concentrations in the stripping phase [6,98].

• Commercial Technologies

Tenova Advanced Technologies (TAT) has developed a lithium recovery process consisting of several steps, including CCAD, nanofiltration, solvent extraction, electrolysis, and crystallization. In the solvent extraction step, the lithium is extracted from the pretreated brine as Li₂SO₄ using Tenova’s solvent extraction method, LiSX™. LiSX™ has a low capital cost of 20% reduction with a compact layout, short construction time, total automatic control, high flux rate, and lower organic losses. It is also easy to operate and maintain. The process succeeded in producing a Li₂SO₄ solution with a purity greater than 99.9%, and lithium recovery of approximately 100% is assumed since lithium in the waste stream was below the 3 mg/l detection limit.

Solvay’s CYANEX^® 936P is a phosphorus-based extractant designed explicitly for extracting lithium (Li) from brines and batteries. It selectively forms a complex with lithium, offering high efficiency, selectivity, and recovery rates greater than 99%. The technology requires filtration pretreatment to remove multivalent ions, has low CAPEX and OPEX, and has low water consumption [111,112].

Adionics has developed a patented technology for selective salt extraction, producing purified lithium chloride-concentrated brine with low energy and freshwater consumption. The technology can be powered by renewable sources, has a concentration factor of up to 20, and reduces CAPEX and OPEX by up to 40% compared to other methods. Testing has been performed on various brines, and a demonstration plant in France operated successfully. In 2023, pilot scale tests in Argentina demonstrated high lithium yield and purity using innovative process steps to produce battery-grade products [113].

Novalith’s LiCAL™ technology directly uses and sequesters carbon dioxide to produce low-carbon, sustainable lithium. It is significantly cheaper, has a smaller footprint, and reduces production costs, plant costs, and plant footprints by up to 65%, 50%, and 25%, respectively. The process uses up to 90% less water, generates no harmful bulk wastes, and emits less CO₂ per ton of lithium chemical produced [114,115,116]. For more information on each company, refer to the Supplemental Information Section S1.

4.2.4. (Electro-)Membrane Separation

Electro-membrane separation encompasses various membrane technologies used for lithium extraction, including electrodialysis (ED), electrodialysis reversal (EDR), electrodialysis with bipolar membranes (EDBM), membrane capacitive deionization (CDI), and nanofiltration (NF) for pre-treatment. The readiness level of these membrane technologies ranges from the laboratory stages to pre-commercial stages (TRL 4–8). Generally, membrane technologies offer several advantages: they provide high lithium selectivity and concentration in the eluate, often exhibit low energy consumption, and can reduce or eliminate the need for chemicals. Additionally, these technologies are capable of continuous operation [6,48].

• Nanofiltration (NF)

Nanofiltration is a pressure-driven membrane separation process that utilizes the Donnan and size-screening effects to achieve filtration capabilities. It demonstrates superior retention of multivalent ions while allowing higher permeability for monovalent ions. Typically employed for brine pre-treatment to remove divalent ions, nanofiltration can also be used for lithium extraction. Recent advancements include the development of polymer-functionalized metal-organic framework (MOF) nanofiltration membranes that offer exceptionally high selectivity and rapid separation of Li⁺. Ongoing research aims to enhance these membranes further to improve lithium selectivity and efficiency in separating lithium from solutions rich in monovalent ions [6].

Nanofiltration is an up-and-coming technology across various scales due to its moderate cost, low environmental impact, and high selectivity. However, the high Mg/Li ratio in brine presents a significant challenge, complicating the selective recovery of lithium over magnesium. The Donnan effect allows nanofiltration membranes to reject high-valency cations more effectively than low-valency ones, resulting in better separation of cations. Despite these advantages, “membrane fouling” remains a significant issue, causing a continuous decline in flux and reducing the efficiency of lithium recovery from brine.

Conventional nanofiltration membranes exhibit poor monovalent selectivity in high-salinity environments due to weakened exclusion mechanisms. A study was conducted at the Massachusetts Institute of Technology on developing polyelectrolyte-coated nanofiltration membranes for the selective recovery of lithium from salt-lake brines and battery leachates. The polyelectrolyte coating enhances the Donnan exclusion of multivalent cations like Mg²⁺ compared to monovalent cations like Li⁺, leading to improved selectivity. This is attributed to the high density of positively charged ammonium (NH²⁺) functional groups in the coating. Molecular dynamics simulations have revealed that the NH²⁺ groups create an electrostatic energy barrier that disproportionately impedes the partitioning of multivalent cations into the membrane, facilitating the preferential transport of Li⁺. Despite a 14.7% increase in specific energy consumption, the two-stage NF process using the coated membranes achieved permeate lithium purity exceeding 99.5% from Chilean salt lake brines, significantly reducing residual Mg²⁺ concentration [117].

• Electrodialysis (ED)

Electrodialysis (ED) is a membrane-based process that uses electrodes to generate an electric field, which drives negative and positive ions through semi-permeable membranes. By arranging multiple membranes in sequence, ED alternately allows positively or negatively charged ions to pass through, effectively removing them from the brine. This process is often employed to preconcentrate the brine or enhance water recovery. However, ED only removes charged ions from water, leaving behind noncharged dissolved solids, such as organic matter and silica. Therefore, pre-treatment is necessary to eliminate these noncharged solids from the feed before they enter the system. The driving force in ED is the electrical potential applied across the membranes. Selective ion exchange membranes are crucial for effectively applying electrodialysis, particularly in extracting lithium from salt lake brines with high Mg/Li ratios [6,118,119].

In electrodialysis (ED), charged suspended solids can significantly increase the membrane’s resistance, which impairs the process’s efficiency. This issue can be mitigated by reversing the polarity of the applied electrical potential, a process known as electrodialysis reversal (EDR). EDR helps remove charged particles that have precipitated on the membranes by periodically reversing the direction of the electric field. Unlike ED, where the driving force is the electrical potential, EDR relies on the concentration difference as its driving force. By alternating between these two processes and changing the current across parallel membranes, the system can self-regenerate, reducing the need for frequent stops and minimizing membrane fouling.

The average lifespan of an ED membrane is typically between 5 and 7 years. ED and EDR processes can achieve very high-water recovery rates without using chemicals, although adding an antiscalant can further enhance salt tolerance. One of the main limitations of ED/EDR is the current density limit; exceeding a specific current density can cause water dissociation into H⁺ and OH⁻ ions, which can disrupt the process. Additionally, while electrodialysis with monovalent-selective ion exchange membranes can effectively remove divalent ions, efficiently recovering lithium from brines containing coexisting monovalent ions (such as Na⁺ and K⁺) remains challenging [6,118,119]. ED requires a monovalent ion-exchange membrane for selective Li recovery to separate monovalent ions from divalent ions. Using a monovalent cation exchange membrane, Li recovery can reach up to 95% from synthetic brine with a high Mg/Li ratio (~150) [120].

In a new development, the typical CEM membrane separator is replaced with solid-state electrolytes (SSE). SSEs are rigid, three-dimensional cation-anion frameworks that allow the migration of mobile cations such as lithium ions. The transport of mobile cations is facilitated through the migration of defects in the crystalline structure. The effectiveness of extraction depends on the SSE materials and pores size. A few studies have shown that SSE materials could be used to extract lithium ions from seawater selectively. Regardless, fundamental evaluation and understanding of transport in SSEs applied to aqueous systems remains almost unexplored [121].

• Electrodialysis Bipolar Membranes (EDBM)

Electrodialysis bipolar membrane (EDBM) is an advanced ED/EDR technology that uses brine to produce acid and base alongside diluted water. Unlike typical ED/EDR systems, EDBM intentionally exceeds the current density limit beyond the point of water dissociation, causing water to split into H⁺ and OH⁻ ions. The type of acid and base produced depends mainly on the ionic composition of the brine. To enhance the purity of the resulting products, pre-treatment of the brine and adjustments to current and membrane characteristics can be implemented. Additionally, the concentration of these products can be precisely controlled. A key advantage of EDBM is the absence of electrode reactions, which means no by-products are generated in the system.

An emerging variation of this technology is Selectrodialysis bipolar membrane (BMSED), which combines the principles of Selectrodialysis (SED) with EDBM to refine the process further. In the context of lithium extraction, EDBM is particularly effective at producing lithium hydroxide (LiOH) from brine. However, in seawater brine, which contains a high concentration of sodium ions (Na⁺), the process is more likely to favor the production of sodium hydroxide (NaOH) [6,118,119].

• Membrane Capacitive Deionization (CDI)

Capacitive deionization (CDI) is a distinctive system that stands apart from other electromembrane technologies. In simpler terms, CDI works by passing brine between a pair of positively and negatively charged electrodes made from a porous material. This setup causes the ions in the solution to be attracted to and stored on the surface of the electrodes, resulting in a diluted water solution. Once the electrodes reach saturation, the polarity is reversed, releasing the ions back into the solution and creating a more concentrated brine. One of the main advantages of CDI over other electromembrane technologies is its reduced need for pre-treatment. Additionally, CDI operates at a relatively low voltage (less than 1.8 V), requiring less energy while still achieving substantial water recovery. The system’s flexibility allows it to be adjusted to separate and enhance the purity of specific products through additional pre- and post-treatment steps. Another benefit of CDI is that it does not require high-pressure pumps or heat sources, as it functions effectively under ambient conditions [6,46,118,119].

The efficiency of CDI depends on three main factors: electrode material, Electrolyte concentration, and Electrode spacing. Electrode spacing affects the system’s energy loss. Reducing the spacing can reduce the energy loss in CDI and shorten the transport distance and time of ions in the electrolyte solution, thus reducing the resistance to ion transfer in the solution. Electrolyte concentration plays a primary role in reducing the system’s energy consumption and improving efficiency. The more concentrated the feed solution, the lower the ionic resistance and the less energy consumed by the system. Regardless, reducing electrode spacing and increasing electrolyte concentration would lower feed capacity and increase the scaling potential. Electrode material affects the electro-sorption capacity of the CDI (Figure 10). The preferred choices for CDI electrode materials are high specific surface area and low resistivity active materials. The high specific area allows for more transportation, and the low resistivity reduces ion transport resistance [122]. In addition to the specific area and low resistivity, the electrode’s hydrophilicity significantly affects the CDI’s efficiency. A hydrophilic electrode surface prompts the formation of hydrogen bonds with water molecules, facilitating the adsorption of ions onto the electrode surface [123].

Monovalent-selective cation exchange membranes can effectively block multivalent cations. However, conventional capacitive deionization (CDI) systems are generally ineffective at removing monovalent cations like sodium (Na⁺) and potassium (K⁺) from brine. To overcome this limitation, the use of lithium-selective membranes, such as those combining PVC-diethylene tetra-amine with lithium-manganese-titanium oxide (LMTO) selective adsorbents, has been shown to increase the adsorption capacity for lithium ions (Li⁺) by 60%, while also reducing energy consumption [6,122]. In a 2024 study, using a Li_(4C-40%)FePO₄ electrode enhanced the selectivity of lithium in simulated seawater brine with purity of 97.94%. The Li_(4C-40%)FePO₄ lamellar structure’s short ion diffusion path favored Li⁺ diffusion [126]. Despite these promising results, further development is necessary to make CDI a viable option for efficient lithium extraction at industrial scale [46].

CDI technology can be applied in various industrial fields, including chemical, pharmaceutical, electronic, and petroleum industries, to purify different solutions. The energy consumption in the CDI process mainly includes energy losses due to system resistance and leakage current. The losses are primarily due to the storage and release of ionic substances in the electrodes. The resistance mainly comprises electronic resistance in the wires, current collectors, between the current collectors and electrodes, and ion transport resistance in the pores of the electrode and spacer channel [122].

Optimization of energy efficiency can be achieved through energy management and energy recovery. Energy management can be divided into three categories, ion resistance reduction, electron resistance reduction, electrolyte oxidation reduction, and reducing electrode corrosion. Increasing electrolyte concentration will enhance conductivity, which in turn will minimize ion resistance. This is suitable for seawater desalination, but the material cost will be high. Another method is shortening electrode distance, which will also reduce ion resistance, and would be suitable for small-scale water treatment and not for large-scale operations. A high porous surface area will also help minimize ion resistance, which is ideal for various solutions and will increase stability. Reducing electron resistance can be achieved using high-conductivity composite materials such as CNT/rGO. This is suitable for the industrial scale, but at a higher cost. Redox pairs and polymetric materials will also reduce electron resistance and are ideal for industrial-scale operations. Electrolyte oxidation reduction can be achieved using nitrogen purging, suitable for long-term stable operation. The optimization of the electric field mode and the feed flow rate will also reduce electrolyte oxidation and is ideal for long-term stable operation. Additionally, polymer protective film on the surface will help protect the electrode from oxidation by blocking oxygen, significantly improving the stability in the long-term. MXene and titanium oxide composite material will enhance the corrosion resistance of the electrode in the long term [122].

Energy recovery can be divided into direct and indirect recovery. Direct energy recovery can be accomplished by connection of charge/discharge units, which would be suitable for simple systems and have a low cost of implementation. Another way of achieving direct energy recovery is by using a DC-DC converter to improve energy transfer efficiency, which would be more suitable for large-scale systems and have higher efficiency and stability. Using series/parallel combinations of multiple units will also enhance energy recovery for large-scale systems. Indirect energy recovery can be accomplished using an energy storage capacitor suitable for continuous CDI processes. A boost-buck converter is another way to achieve indirect energy recovery ideal for large-scale operations. In addition, smart energy management and monitoring systems will also help with energy recovery for long-term industrial operations [122].

• Commercial Technologies

Membrane and electro-membrane industry developers have lately been moving towards utilizing their technologies for DLE systems. Companies such as Veolia, Saltworks, Tenova, and DuPont currently offer specialized DLE systems technologies. Other companies like Summit Nanotech, EnergyX, Evove, and Conductive are joining the race soon. The following are companies with membrane DLE systems, ranked from most advanced to least. Tenova, Summit Nanotech, EnergyX, and Conductive are excluded to avoid repetition [122].

Veolia Group offers innovative solutions for water and energy management, specializing in lithium processing technologies. Their goal is to lower production costs, increase yield, and maximize returns for clients in the lithium industry. They provide complete processing systems and a broad portfolio of technologies for integrated flowsheets, emphasizing efficiency and cost-effectiveness [127].

Saltworks specializes in innovative solutions for industrial wastewater and refining lithium. The company utilizes Concentrating, Refining, and Converting (CRC) technology downstream of DLE to produce battery-grade lithium carbonate or hydroxide. Their offerings include BrineRefine, XtremeRO and OARO, BrineIX, LcRx, and a high-purity lithium carbonate production unit. These technologies enable the treatment of more concentrated brines, higher freshwater recovery, and high-purity lithium production [128].

DuPont Water Solution’s FilmTec™ technologies include the high-productivity nanofiltration membrane element FilmTec™ LiNE-XD, which is used for lithium brine purification. The technology is utilized for lithium stream purification in chloride-rich brine mining, and it leverages high monovalent-divalent ion selectivity and state-of-the-art membrane chemistry. This technology offers high lithium passage for typical chloride-rich Li-brine streams, provides optimized membrane chemistry for a reliable element lifetime, and allows for increased water and lithium recovery with reduced energy consumption [129].

Evove’s DLE system is a two-stage process with low energy, chemical, and water consumption and a compact footprint. It provides >90% lithium recovery with 99.5% purity and a capacity of 4 tons LCE/LHM per year. The process comprises separation using nanofiltration membranes and polishing the brine with ion exchange to produce battery-purity lithium chloride [130].

ElectraLith’s patented DLE-R technology revolutionizes the direct lithium extraction and refining industries, eliminating the need for water and chemicals. It can operate entirely on renewable power, producing lithium hydroxide in a single step. The system is modular and scalable and is applicable to any lithium source, with lower costs and higher recovery rates. ElectraLith is currently testing its technology on brines from Rio Tinto’s Rincon project [131].

SiTration is developing chemical-free, energy-efficient extraction and recycling systems to lower costs and resource intensity in the materials supply chain. They aim to design a durable, modular, and scalable solution for lithium battery recycling, mining, and refining applications. They are also developing a new filtration membrane for selective lithium extraction [132].

Alma Energy utilizes clean, emission-free processes for lithium extraction from natural brines. Their technology aims to be carbon-negative, producing lithium products, green hydrogen, freshwater, and CO₂ sequestration as by-products. This technology is adaptable for various applications, from wastewater treatment to lithium battery recycling [133]. For more information on each company, refer to Supplemental Information Section S1.

4.2.5. Electrochemical Separation or Refining

The final route for direct lithium extraction (DLE) leverages electrochemical principles to extract lithium, utilizing reversible electrochemical reactions like those in electrolysis. The technological readiness of electrochemical separation methods varies widely, ranging from laboratory research to pre-commercial stages (TRL 3–8). This approach offers unique advantages akin to the Li⁺ intercalation/deintercalation process used in lithium-ion batteries. Specifically, the working electrode can function as an ion sieve, selectively capturing Li⁺ from brine and releasing it into the recovered solution. This method also prevents acid elution during the dissolution of the ion sieve, which is a common issue in other methods. For effective lithium extraction, the electrodes used in this process must exhibit high selectivity for lithium, possess substantial lithium capacity, consume minimal energy, and maintain stability over long-term operation. One of the essential requirements is that the electrodes must be capable of quickly absorbing and releasing the desired ions by simply adjusting the electrochemical potential [6,46,49].

The electrochemical extraction’s driving force for lithium capture is the application of an electrical potential bias between electrodes. The technology can be classified into three general categories: battery-based, battery-based combined with the membrane, and electro-membrane-based. Electro-membrane-based approaches, also known as electrodialysis (ED) systems, have been described in the membrane separation section. CDI membrane technology, which has also been mentioned previously, is considered battery-based combined with the membrane system. Other systems include rocking chair and redox battery systems. In battery-based systems, the selective lithium ion electrodes use a Faradaic process to capture lithium ions. Battery-based systems can be divided into electrochemical ion-pumping systems (EIPS) and electrochemical switched ion exchange (ESIX) based on the type of counter electrode. EIPS are also divided into battery-operating EIPS and mixed-ion battery EIPS. In EIPS, the counter electrode, or the non-lithium ion selective electrode, is faradaic. In ESIX, the counter electrode is non-faradaic. The difference between faradaic and non-faradaic processes is the transfer or non-transfer of charge across the fluid–solid interface. In battery-operating EIPS, a lithium-ion selective electrode is paired with an electrode made from Pt or Ag, which does not react with lithium ions. A lithium ion exclusive material is usually applied in mixed-ion battery EIPS and ESIX systems for lithium ion extraction. Mixed-ion battery EIPS uses a faradaic lithium ion exclusive counter electrode, whereas ESIX uses a capacitive or pseudocapacitive counter electrode [50].

The battery-based electrochemical process has four steps. The first step is extracting lithium ions from brine into the lithium-ion selective electrode. The second step is exchanging the brine with a recovery solution. The third step is releasing the lithium ions from the lithium-ion selective electrode. Finally, the recovery solution is replaced with the brine so that the cycle can begin again. In battery-based electrochemical systems, the ion selectivity is not enabled by a membrane but by the properties of the lithium-ion selective electrode. The faradaic EIPS system has the advantage of lower self-discharge and a larger capacity. In contrast, the ESIX system with a non-faradaic electrode has the advantage of faster removal rates [50].

• Electrocoagulation (EC)

Electrocoagulation is a wastewater treatment process that uses an electrical current to remove pollutants from water. By applying an electrical current to a pair of submerged electrodes in a reactor unit, the metal ions are oxidized on the surface of the anode and scattered into the water, and hydrogen and hydroxide are released from the cathode. As the electrons move from the anode to the cathode, the metal ions react with hydroxide ions, forming metal hydroxides. The metal hydroxides act like a magnet, attracting and encapsulating impurities in the water, forming flocks. These flocks are large enough to be easily separated [134,135].

EC is more of a precipitation process than an electrochemical process. It has been developed and used industrially for wastewater treatment. The EC process can take between 3 and 6 h. It is employed to remove various pollutants, such as heavy metals, anions, and organic matter. Compared to other wastewater treatment technologies, the EC process has the advantages of a higher removal efficiency of pollutants, lower energy consumption, and eco-friendliness. Lately, a few studies have been conducted to apply EC technique to lithium extraction. Removing lithium from a solution with a high Mg/Li ratio has been proven to be challenging due to the similar properties of both elements. EC with aluminum electrodes can be used for lithium extraction, forming the following reaction:

LiCl + 2AlCl₃ + 6NaOH → LiCl·2Al(OH)₃·xH₂O + 6NaCl

The EC process is mainly influenced by the current density, which can affect energy consumption and the generation of Al³⁺ and OH⁻. This affects the efficiency of lithium recovery. Higher solution conductivity and shorter electrode spacing would assist with reducing the applied voltage and thus energy consumption. Initial pH can affect the formation of Al(OH)₃, thereby affecting lithium recovery. A favorable pH range is between 4 and 6.5. A higher initial lithium concentration typically yields better recovery. The studies show that the extraction of lithium from brines is possible. Regardless, the question of economic viability remains. The studies were also performed on brines with Li concentration ranges from 200 mg/L to 1500 mg/L, which is higher than the Li concentration in seawater brine [136].

• Commercial Technologies

In the rocking chair system (battery-based combined with the membrane), two faradaic electrodes intercalate lithium ions, and the cell is divided into two compartments by an anion exchange membrane (AEM). By applying an electric potential between the cathode and anode, one electrode captures lithium ions from the brine compartment and releases them into the recovery solution to the other electrode. Like the rocking chair system, in a redox battery, an AEM separates the system into two compartments. The first compartment captures and releases lithium ions from the lithium-ion selective electrode. In the second compartment, electrodes made of different materials can be used for redox processes [50]. The flexibility offered by the electrochemical method makes lithium extraction a promising and continuous development. The electrochemical method has been used not only on a laboratory and small pilot scales, but also in industrial space, such as by Tenova, Mangrove Lithium, Aepnus Technology, Vito, Ellexco, Lithios, and Electroflow. While using similar methods, these companies can differentiate on their electrochemical technology, pretreatment, Li precursor, energy source, or configuration. For more information on each company, refer to Supplemental Information Section S1.

Many companies use different Li precursors before their electrochemical method. For instance, Tenova Advanced Technologies (TAT) has developed a lithium recovery process consisting of several steps, including CCAD, nanofiltration, solvent extraction, electrolysis, and crystallization. The sequential processes before electrolysis are utilized to produce high-grade Li₂SO₄. The produced Li₂SO₄ solution is sent to the LiEL™ electrolysis process unit, where it is converted into a LiOH solution. Finally, the product is dispatched to the crystallization and drying processes [137,138].

In contrast, Mangrove directly converts raw Li from brines, hard rocks, clays, and DLE into lithium hydroxide or lithium carbonate via the electrochemical method. Mangrove’s Clear-Li™ electrochemical conversion technology lowers the overall carbon footprint of the lithium supply chain and improves environmental, social, and governance impacts. Mangrove’s patented, proprietary technology uses electrochemical processes to convert lithium chloride and lithium sulfate into lithium hydroxide directly. The technology also produces fungible byproducts, boosting the investment rate of return and solidifying project bankability. These byproducts are HCl and H₂SO₄ in lithium chloride and lithium sulfate, respectively. They can be used at the extraction stage to acquire lithium and improve sustainability with a closed-loop extraction process. Mangrove’s innovative refining technology has multiple benefits. This benefit includes direct conversion of lithium chloride to high-purity lithium hydroxide, reduction in overall OPEX of LiOH refining, boosting project viability, and reduction in refinement cost by 40% compared to conventional brine processes. The modular platform can co-locate with existing extraction operations and refine near brines and salars. Modular technology can be quickly scaled to meet capacity requirements and customer battery specifications. The only by-product of the process is HCl, which can be recycled in the DLE process, eliminating the cost of acid consumables [139].

In terms of energy sources, Aepnus technology focuses on utilizing renewable energy. Aepnus ultra-efficient electrolysis runs on renewable electricity to process critical minerals, reagents, or metals at lower costs and associated emissions than the existing technologies. The developed technology is a low-cost electrolysis process that can produce commodity chemicals across sectors using renewable electricity. Aepnus enables the domestic extraction and refinement of battery-grade lithium chemicals to ramp up US battery manufacturing with a fraction of the CAPEX, OPEX, and carbon footprint [140].

VITO has differentiated itself from other companies via its technology. VITO is developing gas diffusion electrocrystallization technology (GDEx). This technology is powered by electricity and converts gases, such as carbon dioxide or oxygen, into substances that selectively react with the desired materials to recover them. This enables valuable raw materials, such as precious metals, cobalt, manganese, and lithium, to be retrieved from aqueous waste streams. The GDEx method has also enabled the extraction of all the lithium in the geothermal brine. In addition, it is an excellent way of selectively recovering the metals if they are present in low concentrations within highly complex solutions. The process is fully powered by electricity, and no additional chemicals are required. This method is also actively under development [141].

Three promising companies, Ellexco LLC, Lithios, and Electroflow, are utilizing electrochemical methods that are early in the development phase. Ellexco LLC offers a chemical-free direct lithium extraction technology from aqueous sources and provides a novel approach to the lithium mining industry. Ellexco’s integrated electrochemical process starts by removing silica from the geothermal brine to prevent scaling. The silica-free brine then undergoes a selective extraction process to recover LiCl. Finally, LiOH is produced using electrochemical technology. This process uses electricity as input, with no added chemicals or waste generated. The method also directly produces lithium hydroxide as the final product [142]. Lithios is a technology company using advancements in applied electrochemistry to extract advanced lithium from challenging mixtures. Its advanced lithium extraction (ALE) technology is still in the laboratory stages. Lithios plans to have its first pilot plant soon, a step toward scaling its electrochemical system. However, more development is still needed for the system to reach its next stage [1]. Lastly, Electroflow is a newly founded American company. It is developing an electrochemical process capable of producing cathode-ready lithium from dilute brine resources. The process is still in its early stages and requires more progress. Electroflow is potentially looking to offer a novel electrochemical technology with further innovative advantages [143].

5. Outlook and Perspective

Lithium, a key component in rechargeable batteries, has seen a significant surge in price over the past decade. This increase is primarily driven by the rapid growth of the electric vehicle (EV) market and the increasing demand for energy storage solutions. Some key factors contributing to the rising cost of lithium are the growing EV market, limited supply, production challenges, geopolitical factors, and increased competition. As the global transition to electric vehicles accelerates, the demand for lithium-ion batteries, which power these vehicles, has skyrocketed. This increased demand has outpaced the current supply, leading to higher prices. The demand for lithium is only expected to rise, most likely exceeding the production capacity by the next few years [144,145].

Lithium is primarily extracted from spodumene and lepidolite. High-quality lithium resources are limited, and new discoveries and developments can take time. Mining and refining lithium can be complex and environmentally challenging. Transportation costs, regulatory hurdles, and technological limitations can constrain production and increase prices. The concentration of lithium production in specific regions, such as South America and Australia, can make the market vulnerable to geopolitical risks. Disruptions in supply due to political instability, trade disputes, or natural disasters can further inflate prices. The urgency of discovering new sources of lithium and overcoming the technical challenges is growing exponentially [144,145]. Figure 11 and

Table 5. Direct lithium extraction developed projects and technologies.

Company	Technology/Project Name	Technology Category	Development Stage	Technology Readiness Level	Lithium Based-Products	Company’s Claims	Logo
Livent	ILiAD	Adsorption	Commercial	TRL 9	Lithium chloride	99.9% impurity rejection >90% Li recovery Li feed concentration of 50–2000 ppm
SUNRESIN	DLE System	Adsorption	Commercial	TRL 9	Lithium carbonate and lithium hydroxide	Production capacity as of 2022 is 4000–25,000 tons/year
Eramet	BofA Li DLE	Adsorption	Demo	TRL 8	Lithium carbonate	90% Li recovery
International Battery Metals	IBAT DLE	Adsorption	Demo	TRL 8	Lithium chloride	95% Li recovery >50 °C operation requirement
KOCH	Li-PRO™	Adsorption	Demo	TRL 8	Lithium chloride	95% Li recovery
Summit Nanotech	denaLi™	Adsorption	Demo	TRL 8	Lithium carbonate	>90 Li recovery
		Membrane
ENERGYSOURCE MINERALS	ATLiS	Adsorption	Demo	TRL 8	Lithium chloride	7 to 80 times less footprint (than conventional) 3 to 9 times less water consumption (than conventional) 2 to 8 times less CO2 emission (than conventional)
Watercycle Technologies	DLEC	Adsorption	Pilot	TRL 6	Lithium hydroxide	>95% Li recovery
Vulcan Energy	Zero Carbon Lithium	Adsorption	Demo	TRL 7	Lithium chloride and lithium hydroxide	>90% Li recovery >50 °C operation requirement
ExSorbtion	CO2 generate DLE	Adsorption	Pilot	TRL 6	Lithium carbonate	Feed concentration as low as 40 ppm 3 tons of water per ton of product
EON Minerals	Amanecer	Adsorption	Pilot	TRL 6	Lithium carbonate	Hybrid system of DLE and advanced evaporation processes
Berkshire Hathaway Inc.	Salton Sea	Adsorption	Pilot	TRL 6	Lithium carbonate and lithium chloride	Capacity of 100 gpm Energy is provided through 100% renewable sources
Rio Tinto	Rincon	Adsorption	Pilot	TRL 6	Lithium carbonate	Capacity of 3000 tons/year
TerraLithium	Proprietary DLE	Adsorption	Pilot	TRL 6	Lithium carbonate and lithium hydroxide	Minimal footprint and environmental impact Replicable design for scale-up and cost efficiency
EnergyX	LiTAS™	Adsorption	Demo	TRL7	Lithium chloride	No chemical usage, 90% Li recovery Process time 1–2 days. Production cost as low as $100/ton
		Solvent Extraction
		Membrane
Precision Periodic	Nano Beads™	Adsorption	Pilot	TRL 5	Lithium chloride	>95% Li recovery, maximum 200 mg/g adsorption capacity
Olokun Minerals	zSMB	Adsorption	Lab	TRL 4	Lithium chloride, lithium carbonate, and lithium hydroxide	>95% Li recovery >99% product purity
Lilac Solutions	Lilac IEX	Ion Exchange	Commercial	TRL 9	Lithium chloride	10 acres footprint Water consumption of 2–20 m3/ton 99% Li recovery
Chemionex	DLE System	Ion Exchange	Commercial	TRL 9	Lithium chloride and lithium carbonate	Focus on low lithium levels from concentrated brine
GeoLith	Li-Capt®	Ion Exchange	Demo	TRL 8	Lithium concentrate (LiCl, Li2SO4)	<90% Li recovery Ability to treat a wide range of feed brine with Li concentration as low as 5 mg/L
Standard Lithium	SLi DLE	Adsorption	Demo	TRL 8	Lithium carbonate	>95% Li recovery 94%–99% impurity rejection
Volt Lithium Corp	Proprietary DLE	Ion Exchange	Demo	TRL 8	Lithium carbonate	98% Li recovery
E3 Lithium	E3 DLE	Ion Exchange	Demo	TRL 8	Lithium concentrate	90% Li recovery 98% impurity removal
Conductive Energy Inc.	Conductive’s IEX	Ion Exchange	Pilot	TRL 6	Lithium chloride and lithium carbonate	95% Li recovery 99.5% product purity
	Conductive’s ED	Membrane
XtraLit	XL-DLE	Ion Exchange	Pilot	TRL 5	Lithium hydroxide	Feed Li concentration 5–300 ppm 95% Li recovery Operation pH 3 to 12
Geo40	Geoseive	Ion Exchange	Pilot	TRL 5	Lithium concentrate	90% Li recovery
Solvay	CYANEX® 936P	Solvent Extraction	Demo	TRL 8	Lithium concentrate	99% Li recovery and product purity High Li/Na selectivity
Adionics	Proprietary DLE	Solvent Extraction	Demo	TRL 8	Lithium chloride and lithium carbonate	Feed Li concentration of 50 mg/L to 50 g/L >90% Li recovery 86%–97% purity of LiCl and >99% purity of Li2CO3
Tenova	LiSX™	Solvent Extraction	Commercial	TRL 9	Lithium sulfate and lithium hydroxide	99.9% Li recovery 88% Ca removal 97% Mg removal 99.9% product purity
	LiP™	Membrane
	LiEL™	Electrochemical
Novalith	LiCAL®	Solvent Extraction	Pilot	TRL 6	Lithium carbonate	Compared to conventional, production cost, plant cost, plant footprint, and water consumption of 65%, 50%, 25%, and 90% less, respectively
Veolia	Proprietary DLE	Membrane	Commercial	TRL 9	Lithium carbonate and lithium hydroxide	90% less water consumption
Saltworks	Li Refining	Membrane	Commercial	TRL 9	Lithium carbonate and lithium hydroxide Concentrated brine stream	99.9 product purity RO membrane can concentrate brine up to 120 bar and 130,000 mg/L feed TDS
Evove	Proprietary DLE	Membrane	Pilot	TRL 6	Lithium chloride and lithium hydroxide	>90% Li recovery 99.5% product purity Capacity of 4 tons LCE/LHM per year
ElectraLith	DLE-R	Membrane	Pilot	TRL 5	Lithium hydroxide	Single-step DLE process
SiTration	Proprietary DLE	Membrane	Lab	TRL 4	Lithium carbonate or lithium hydroxide	Chemical-free process Mainly focus on recycling Li battery
Mangrove Lithium	Clear-Li™	Electrochemical	Demo	TRL 8	Lithium carbonate and lithium hydroxide	Refine LiCl or Li2SO4 to Li2CO3 or LiOH Reduce refinement cost by 40% compared to conventional
Aepnus Technology	Proprietary DLE	Electrochemical	Pilot	TRL 5	Lithium carbonate or lithium hydroxide	Extraction of various cations No chemicals
Lithios	ALE	Electrochemical	Lab	TRL 3	Lithium carbonate and lithium hydroxide	Uses minimal power and freshwater Chemical-free Wide range of brine and concentrations
VITO NV	GDEx	Electrochemical	Lab	TRL 4	Lithium carbonate	Gas-diffusion electrode Low carbon
Ellexco	Proprietary DLE	Electrochemical	Lab	TRL 3	Lithium chloride and lithium hydroxide	Chemical-free
Electroflow Technologies	Proprietary DLE	Electrochemical	Lab	TRL 3	Lithium concentrate	Treat brine with 10–200 ppm Li concentration 90% Li recovery
Sorcia Minerals	Proprietary DLE	Adsorption	Commercial	TRL 9	Lithium chloride, lithium carbonate, and lithium hydroxide	Li extraction efficiency of 75%–90% Recycle > 98% of process waters
Alma Energy	Proprietary DLE	Membrane	Lab	TRL 3	Lithium carbonate and lithium hydroxide	No chemicals Emission-free
Lithium Harvest	Proprietary DLE	Adsorption	Commercial	TRL 9	Lithium carbonate	96% less water consumption of 20 million gal per 1000 mt LCE consumption (than conventional) 70% lower CAPEX (than conventional) and 35% lower OPEX (than conventional) >95% Li recovery footprint of 1.4 acres per 1000 mt LCE (99% lower than the conventional)
DuPont	FilmTec™ LiNE-XD	Membrane	Commercial	TRL 9	Monovalent rich brine	99.2 salt rejection high monovalent-divalent ion selectivity

show the TRL levels and technologies for various lithium extraction methods from seawater brine discussed in this study. TRL represents the readiness level of the system with existing lithium sources, such as salar brines; however, the use of the system with new and potential sources, including geothermal and seawater, remains undetermined.

As the demand for lithium grows, more players are entering the market. This increased competition can lead to higher bidding prices for lithium resources, driving up costs for downstream industries (Figure 12). The rising cost of lithium has implications for various sectors, including the automotive industry, electronics, and energy storage. While efforts are underway to increase lithium production and explore alternative battery technologies, the overall trend suggests that lithium prices will likely remain elevated for the foreseeable future [137,138].

As the quantity of lithium in seawater eclipses the amount on land, seawater holds the potential to become the primary source of lithium. The advantages are numerous: it is available worldwide, contains more lithium than inland sources, and increased demand for seawater desalination results in seawater brine becoming a common waste byproduct. DLE technologies offer a cleaner, cheaper, and more environmentally friendly solution to current technologies, and they can be adapted to extract lithium from seawater. However, the challenges are significant. The main difficulties of extracting lithium from seawater are the low lithium concentration and the high Na/Li ratio. The separation of lithium from a sodium-rich solution is challenging due to their similar chemical properties, and concentrating seawater brine is both costly and energy-intensive. Seawater brine requires multi-stage pretreatment, such as removing multivalent ions and concentration, adding to the overall cost. Additionally, because of the low lithium concentration, product purity and lithium recovery are lower, necessitating additional extraction stages and post-treatment. Corrosion-resistant, expensive materials are required due to the brine’s high salinity, which increases CAPEX. The high salinity also raises the probability of scaling, increasing operation costs due to frequent cleaning and the use of anti-scaling chemicals. Technological advancements are critically needed to reduce energy and water consumption, production costs, and environmental footprint. DLE technologies are evolving quickly, with new studies being published monthly. Some are in early stages, while others are scaling to industrial levels. Technologies like electrocoagulation, well-established in wastewater treatment, are being explored for lithium extraction due to rising demand. Research and development of new technologies is focusing on innovative approaches to improve efficiency and reduce costs. For example, researchers are developing advanced membranes with high selectivity for lithium ions, which could significantly enhance the extraction process. Additionally, there are efforts to integrate renewable energy sources, such as solar and wind power, into the DLE process to further reduce energy consumption and environmental impact. Moreover, nanotechnology is being explored to create highly selective and efficient adsorbents for lithium ions. These nanomaterials could potentially revolutionize the extraction process by increasing the selectivity for lithium, thereby reducing the need for extensive pretreatment and post-treatment stages.

It is critical to understand that although DLE technologies are advancing rapidly, extracting lithium from seawater brine is still not considered economically viable. Most DLE technologies are tailored to extract lithium from lithium-rich brines. The three main subjects that need to be addressed when applying DLE to seawater are lithium selectivity, green development, and market volatility. The high selectivity of lithium is very critical due to the high non-Li cations/Li ratio and low concentration of lithium. A rise in lithium selectivity will increase the efficiency of the technology, reduce concentration and pretreatment process intensity, and decrease energy consumption. The introduction of green, stable processes and renewable energy sources is essential when developing new technologies. If considered during the design stages, such processes would help reduce the environmental impact and lower future costs by reducing adjustments due to more environmental regulations. The introduction of renewable energy within the design can reduce the cost of energy. Additionally, green development should help reduce or eliminate the use of chemicals and toxic or non-recyclable materials within the design. The lithium market is well-established, with many major competitors that can sell lithium-based products at lower prices than the cost of lithium extraction from seawater brine with current DLE technologies.

To overcome these technical challenges, financial incentives need to be more generous for start-ups and large corporations that want to become early adopters. Policies need to be issued to enhance development and push for change. Networks must be built to increase cooperation between academia, startups, large corporations, and policymakers. A stable market needs to be established to encourage developers and stockholders to invest their money and time into the technology implementation and development.

6. Conclusions

The escalating demand for lithium, driven primarily by the electric vehicle (EV) market and the need for utility-scale energy storage solutions, underscores the imperative for technological advancements and strategic policy interventions for lithium production. Current lithium extraction methodologies encounter numerous challenges, including environmental concerns and geopolitical risks. The viability of seawater as a primary source for lithium, backed by the emergence of innovative direct lithium extraction (DLE) technologies, offers a promising solution.

Seawater offers a globally accessible source of lithium with higher concentrations than terrestrial sources. With increased use of seawater desalination to meet freshwater demand, brine becomes a common waste byproduct. These DLE technologies propose a cleaner, cost-effective, and environmentally sustainable alternative to conventional lithium extraction methods. Nevertheless, the extraction of lithium from seawater is challenging, due to the low lithium concentration and the high Na/Li ratio. The separation of lithium from such high sodium concentrations remains a significant technical hurdle, and the process of concentrating seawater brine is both costly and energy intensive.

To address the challenges of extracting lithium from seawater, several research needs must be met. Developing advanced membranes with high selectivity for lithium ions will enhance the extraction process. Integrating renewable energy sources, such as solar and wind power, into the direct lithium extraction (DLE) process will reduce energy consumption and environmental impact. Nanotechnology should be explored to create highly selective and efficient adsorbents for lithium ions, potentially revolutionizing the extraction process. Innovative approaches are needed to improve efficiency and reduce costs, including the exploration of technologies like electrocoagulation. Enhancing multi-stage pretreatment processes to remove multivalent ions and concentrate seawater brine will reduce overall costs and increase product purity. Developing corrosion-resistant materials to handle the high salinity of seawater brine will reduce maintenance costs and extend equipment life. Implementing anti-scaling measures to prevent scaling due to high salinity will reduce operation costs and ensure consistent performance. Advancements in technology are critically required to mitigate energy and water consumption, reduce production costs, and decrease the environmental footprint.

To address these technical challenges, it is imperative to provide substantial financial incentives to both start-ups and large corporations willing to pioneer these technologies. Additionally, policies must be formulated to accelerate development and drive innovation. Establishing robust networks to foster collaboration between academia, industry, and policymakers is essential for ensuring a stable and sustainable lithium supply to meet the increasing global demand.