Core Technology Analysis of Lithium Extraction from Salt Lakes (Part 1)



Core Technology Analysis of Lithium Extraction from Salt Lakes (Part 1)

Salt Lake Lithium Extraction

Large scale, low-cost, ideal source for global lithium resource suppliers

Lithium, as the lightest metal element in nature with the lowest standard electrode potential and the highest electrochemical equivalent, is a naturally ideal "battery metal". Therefore, it will have long-term demand rigidity in power and energy storage applications that require high specific energy, and is known as the "white stone of the future".

The global supply system of lithium resources is divided into two major systems: ore lithium extraction and salt lake lithium extraction. Among them, the proportion of lithium resources in salt lake brine types in the global proven lithium resource composition is as high as nearly 60%. If various deep brine and oil and gas field brine are included, their resource scale and prospecting potential will be even more considerable. In addition, the salt lake project has a large scale of individual resources, low operating costs, and great potential for technological progress, so it is expected to become an ideal main source of global lithium resource supply in the future.

The abundance of lithium in the Earth's crust is not low, but high-quality lithium resource projects that are both large-scale, high-grade, and easily exploitable are still scarce globally, and their distribution is uneven. According to USGS statistics, the total global lithium resources in 2021 were 85.56 million tons of metal, equivalent to 119 million tons of LCE, with a total proven reserves of 22.43 million tons of metal, equivalent to 471 million tons of LCE, which is sufficient to support long-term large-scale power and high-end energy storage applications. Among them, China's total lithium resources closely follow the South American lithium triangle, Australia, and the United States, with a global share of 6% and ranking sixth. However, China's high-grade lithium ore resources are relatively scarce.

The mineralization forms of lithium resources are relatively diverse, among which three types dominate: salt lake brine lithium deposits in closed basins, hard rock lithium deposits of pegmatite type (spodumene, perovskite, lithium mica, etc.), and sedimentary rock type clay lithium deposits, accounting for 58%, 26%, and 7% of the total global lithium resources, respectively. The other types include underground oil and gas field brine, geothermal brine lithium, etc. This proportion will dynamically change with the global exploration process, but it can still demonstrate the basic characteristics of lithium resource distribution in the crust. As of now, the main sources of commercial exploitation are hard rock and salt lake lithium mines. In the next 3-5 years, some high-grade clay lithium mines worldwide are expected to join the supply camp, and comprehensive utilization of potassium lithium resources in deep brine and geothermal brine is also being tested.

Focusing on salt lakes, they are mainly formed in closed basins with arid and semi-arid climates in high-altitude areas, and underground hot springs or rivers bring lithium resources into long-term accumulation. There are four representative salt lake mineralization areas worldwide (the Western Salt Lake Area in the United States, the South American Salt Lake Area, the Dead Sea in West Asia, and the Salt Lake Area in China), each with its own unique resource endowments. According to the statistics of the Ministry of Natural Resources in 2019, the lithium resource potential of brine in China is 92.5 million tons of lithium chloride, and the identification rate is only 19%, accounting for 78.8% of China's overall lithium resource potential. It is mainly distributed in Qinghai (salt lake), Xizang (salt lake), Dazhou in Sichuan, Qianjiang in Hubei (underground oilfield brine) and other places. Although there are also important potash fertilizer production bases such as Lop Nur in Xinjiang, the average lithium content of raw brine is low.

Among them, Qinghai Salt Lake belongs to salt lake brine with high magnesium lithium ratio, low lithium ion concentration (even ultra-high magnesium lithium ratio), and lithium is mainly used as a byproduct of potassium and boron; Due to the early construction of large-scale potassium fertilizer production capacity, it has supporting advantages in salt fields, infrastructure, energy costs, and logistics transportation; After achieving breakthroughs in the technical difficulties of extracting lithium from high magnesium lithium ratio brine, the lithium extraction capacity of Qinghai Salt Lake is currently in a period of rapid growth.

In contrast, the Xizang Salt Lake Project has generally higher lithium ion concentration, surface brine (Qinghai is intercrystalline brine), and more abundant fresh water resources in the mining area. However, due to the weak power system, difficult high-altitude conditions (devices also need additional running in), and strict environmental requirements, it has not been fully developed at this stage, mainly in the establishment of individual "demonstration projects". The deep brine and oilfield brine located in Qinghai, Sichuan, and Hubei are currently in the exploration and testing stage, with great resource potential. However, the cost of drilling, the sustainability of brine extraction, whether tail brine can be reinjected, and the feasibility of comprehensive utilization are constraints on the commercial exploitation of such resources.


Technological upgrade iteration acceleration

From relying on "salt field evaporation and beach drying" to "industrial continuous production"

The process of extracting lithium from salt lakes is complex and simple, which can be divided into lithium extraction (concentration, separation) and lithium precipitation. The core technology is lithium extraction, and lithium precipitation is relatively standardized. Despite high expectations for salt lake development, up to now, nearly 60% of lithium resource supply is occupied by lithium extraction from ores, mainly due to various constraints on the release of salt lake lithium production capacity:

(1) Salt lakes are mainly formed in closed basins in high-altitude arid/semi-arid areas, with weak infrastructure and harsh operating conditions, as well as fragile ecology and strict environmental requirements;

(2) The main lithium rich salt lakes around the world mostly use precipitation technology (except for Livent's Hombre Muerto which uses adsorption), requiring the construction of large-scale salt fields, resulting in high initial Capex costs and long construction cycles. Moreover, the evaporation precipitation method is only suitable for high-quality salt lake brine with high lithium ion concentration and low magnesium lithium ratio, otherwise the efficiency will be greatly reduced;

(3) According to the process flow of the salt field precipitation method, it is necessary to first remove sodium, extract potassium, and then extract lithium. As a result, the expansion of lithium carbonate production capacity also depends on the production scale of front-end potassium fertilizer, and the production stability of salt field evaporation is closely related to natural factors such as rain, snow, and flash floods;

(4) The chemical composition of salt lake brine varies from lake to lake, making it difficult to simply replicate production lines and often requiring one process per lake, resulting in a longer production capacity running in cycle;

(5) Unlike solid lithium mines where resources exist statically, salt lake brine is dynamic. Therefore, salt lake development requires detailed research and scientific planning of the lake's hydrology, otherwise problems such as unexpected brine extraction and rapid decrease in brine concentration in the mining area may occur;

(6) Global excellent and experienced technical teams are scarce.

However, we have noticed that with the outbreak of downstream demand in the lithium industry, salt lake lithium extraction technology has been accelerating its transformation and upgrading iteration in the past 3-5 years. The overall trend is to shift from relying on "salt field evaporation" to "industrial continuous production". In the future, it may change the ecology of the lithium industry in the following six aspects:

Shorter lithium extraction cycle and more efficient production: fully utilizing the high evaporation rate (abundant solar and wind energy) of the mining area to gradually spread and sun in the salt field system, achieving lithium enrichment and partial impurity removal, is the essential reason for the low cost of lithium extraction in salt lakes. However, it also brings drawbacks such as long brine extraction cycle for expansion, large amount of lithium entrainment and loss in the large salt field system, and susceptibility of brine mining areas and salt fields to seasonal rain, snow, and flash floods. The future lithium extraction technology will add new devices in the concentration and separation process, using industrial continuous production to improve efficiency and achieve lower grade brine lithium extraction. By moving forward in the lithium extraction process to avoid or reduce entrainment losses, and through technological innovation in lithium extraction materials and devices, the Capex intensity of energy production will be reduced.

Lithium from by-product to main product: except for a few cases, lithium extraction from salt lakes currently in production is mainly a by-product after potassium extraction, but in the future, lithium will be more common as the main product in the development and design of South American salt lakes and Xizang salt lakes in China.

From extensive to refined: mainly reflected in improving the overall recovery rate from salt fields to workshops, clarifying the reasons for the loss of potassium and lithium in each link and proposing solutions, increasing the recycling and utilization of lithium mother liquor, and optimizing the quality of lithium salt products in the backend (currently, salt lake lithium carbonate has high sodium, magnesium, chlorine, boron impurities, poor consistency, and other problems).

From a single product to diversification and higher added value: In the past, the approach was more focused on pursuing low-cost mass production of industrial grade lithium carbonate as a basic lithium salt, and further purifying, removing impurities, and processing it into various lithium compound products; The future design concept is not only to shift towards direct production of battery grade lithium carbonate, but also to produce a variety of products such as lithium carbonate, lithium chloride, lithium hydroxide, lithium phosphate, etc. in one step, and to extend and build deep processing production lines for metallic lithium in the backend.

Pursuing a lower environmental footprint: The process of extracting lithium from salt lakes varies from lake to lake and is tailored to local conditions. However, regardless of the process, reducing environmental footprint, energy consumption and carbon emissions, freshwater consumption, and brine extraction will become key considerations.

Combining with new energy: Most salt lake mining areas face constraints from industrial electricity, steam and other public facilities, but solar energy is abundant, and the use of clean energy supply forms such as photovoltaic power generation and photothermal power generation (steam supply) coupling and complementing is more common.


Diversified Salt Lake Lithium Extraction Technology Breakthrough Commercialization

Efficient adsorption stands out in practice

In the South American "lithium triangle" region where lithium rich salt lakes are concentrated, salt lake resources are very suitable for salt field evaporation precipitation to achieve concentration and separation due to their superior brine endowment (high lithium ion concentration, low magnesium lithium ratio). Despite being the world's first salt lake lithium extraction project using a new technology (adsorption), Homere Muerto, a subsidiary of Livent (formerly FMC Lithium), was commercialized and put into operation in 1998. However, its production and reaching capacity have not been smooth sailing, and subsequent expansion of Atacama salt lake in Chile, as well as most green space projects such as Agentin Olaroz, Cauchari Olaroz, 3Q, Sal de Vida, still choose to use traditional evaporative precipitation processes.

In Qinghai, China, due to the high magnesium lithium ratio and even low lithium ion concentration of salt lake brine, relying solely on salt field precipitation is not suitable. Therefore, innovative technologies and devices have to be used for concentration and separation after sun drying, sodium removal, potassium extraction, and finally enrichment to a certain lithium ion concentration. After decades of experience in grinding a sword (a costly "industrial experiment"), the processes of calcination, adsorption, electrodialysis, extraction, and gradient membrane method have all been industrialized. After continuous technological improvements, some of them have achieved good results.

It can be said that due to the lack of resource endowments in South American salt lakes, the technological level of lithium extraction in Qinghai salt lakes has actually achieved global leadership. The above process routes have both advantages and disadvantages, but considering the tolerance, yield, energy consumption, environmental protection, and economy of lithium ion concentration in brine, "adsorption+membrane separation coupling" has become the preferred choice in the industry, with efficient and long-cycle adsorbents forming the core barrier.

From "extracting lithium from old brine" to "extracting lithium from original brine", further progress. The above-mentioned breakthroughs in diversified salt lake lithium extraction technology in Qinghai are still based on the "old brine lithium extraction" after evaporation and precipitation, which solves the problem of magnesium lithium separation. However, it still cannot be separated from a large salt field system and a long-term brine drying process. With further breakthroughs in adsorbent performance, from the second half of 2021 to 2022, in salt lakes with relatively high lithium ion concentrations in Qinghai, "lithium extraction from raw brine" has begun to move towards industrialization, and commercial production capacity has begun construction. In the future, it is expected to truly achieve efficient, refined, and low environmental footprint lithium extraction production.


"Adsorption+Membrane" stands out

The process design for lithium extraction from salt lakes needs to vary from lake to lake and be tailored to local conditions. But in the larger process system, it can be divided into salt field precipitation method, as well as multiple new technological paths including electrodialysis, nanofiltration membrane method, extraction method, adsorption method, etc. The core problem solved is "magnesium lithium separation". The two have a special diagonal relationship in the periodic table of elements, and their properties are similar, making separation difficult.

Based on the experience of Qinghai, we tend to believe that the coupling process of adsorption+membrane separation is more promising, mainly because it conforms to the two major industry trends of "moving forward in lithium extraction" and "developing low-grade, low-cost, and green salt lake lithium extraction technology". It has been fully validated, and there is still a lot of room for optimization and improvement from adsorption materials to adsorption devices in the future. Meanwhile, due to the advantages and disadvantages of each process route, it is usually integrated and combined in practice, rather than fighting alone. For example, Lanke Lithium achieved breakthroughs through the coupling of adsorption and membrane separation. The gradient membrane rule is a combination of different membranes, and there is a possibility of integrated application of adsorption+electrodialysis, adsorption+extraction in the future.

At the same time, in order to improve the recovery rate and extract lithium completely, different processes may be used for lithium recovery from the main process production line's lithium precipitation mother liquor (there is no need to go back to the source again). For example, Zangge uses extraction method for lithium precipitation mother liquor recovery, while Hengxinrong uses lithium phosphate path.

In addition, for green land projects with weak infrastructure in Xizang and Argentina in China, some pragmatic resource providers prefer to use the classic evaporation precipitation and other mature processes in the first phase of production capacity. After the supporting conditions are gradually complete and the team is more complete, the new processes with higher mechanization and higher technical requirements will be evaluated in the second phase of production expansion to gradually implement process upgrading.

In addition, it is worth noting that emerging technologies and processes in salt lake lithium extraction, such as adsorption, extraction, and membrane separation, have mature applications in industrial metal and rare earth extraction, medicine, chemical industry, food, environmental protection, and other fields. However, in the field of salt lake lithium extraction, customized research and development, as well as running in and debugging, need to be carried out according to specific brine components and more stringent ecological and environmental requirements in salt lake mining areas, It is not possible to directly transplant flowers and trees. Overall, the space for technological progress in the lithium industry is vast, and with the entry of more experienced and capital strong global cross-border players, it is expected to increase the slope of the growth curve of salt lake lithium extraction technology.


Salt field precipitation method

The traditional classic craftsmanship that best conforms to natural laws is suitable for high-quality low magnesium lithium salt lakes in ideal climates.

The salt field precipitation method is the earliest and most mature classic salt lake lithium extraction process widely used in practical applications. Essentially, the precipitation method utilizes the abundant natural solar energy (high evaporation rate) in salt lake mining areas for stepwise impurity removal and enrichment separation concentration, scientifically following the precipitation sequence of sodium, potassium, magnesium, lithium, etc. under natural conditions. Therefore, the precipitation method can achieve low production costs of lithium carbonate, while consuming less fresh water, relatively low overall energy consumption, and low-carbon environmental protection. As a typical example:

(1) SQM utilizes evaporative precipitation in Atacama Salt Lake, Chile. During the process of enriching the original brine with 0.2% lithium content by 30 times to 6% lithium content (12-18 months), 95.8% of energy consumption is solar energy;