Hydrochemistry, Distribution and Formation of Lithium-Rich Brines in Salt Lakes on the Qinghai-Tibetan Plateau

Lithium isotopic composition of the carbonate type salt lake in Tibet and its implication for origin and hydrological processes

The implementation of the carbon peaking and carbon neutrality strategy has led to a steady increase in the supply of lithium resources. Brine is one of the important sources of lithium, and the extraction of Li from carbonate-type brine is particularly straightforward. Research into the source of materials and hydrological processes of brine is crucial for the sustainable development of lithium in carbonate-type brine. As a fluid-mobile and metallogenic element, lithium has a significant mass difference between its stable isotopes (7Li and 6Li), leading to isotopic fractionation. In this study, we analyzed the hydrochemistry and Li isotope compositions of samples collected from a Li-rich salt lake (Bangor Co) in the Qinghai-Tibetan Plateau. The samples included lake brines, recharge rivers, cold springs, and salt minerals (hydromagnesites). The Li content in the various types of water varied significantly, ranging from 0.06 mg/L to 198.10 mg/L, showing a variation of 4 orders of magnitude. Water samples exhibit a wide range of δ7Li values, varying from 4.89‰ to 16.02‰. Notably, the lowest and highest values are observed in cold springs. Additionally, the concentrations and δ7Li values in hydromagnesite differ across various relative ages. The hydrochemistry indicated that the recharge water is influenced by rock weathering, but the lake brine is influenced by evaporation concentration. The analysis of trace elements and Li isotopic data reveals that rock weathering, geothermal systems, salt minerals, and freshwater, primarily from early geothermal activities and the redissolution of carbonate minerals, contribute to the Li in salt lake brine. Boron isotopes and lithium isotopes of lake brines are found to vary differently. The δ7Li in brine is increased significantly by adsorption of hydromagnesite. And 11B gradually accumulates in hydromagnesite. This study has demonstrated that hydromagnesite plays a crucial role in influencing the characteristics of Li in brine.

Hydrogeochemical characteristics and evolution of formation water in the continental sedimentary basin: A case study in the Qaidam Basin, China

In deep formations, oil or gas reservoir rocks are generally accompanied by groundwater with high total dissolved solids (TDS), commonly referred to as "formation water". The enrichment of trace and/or metallic elements such as K, B, Li, Br, Sr in this type of groundwater holds significant industrial values and socioeconomic benefits. However, the processes involved in the burial and generation of formation water remain not fully understood. In this study, totally 468 sets of major ions and trace elements were collected from current study and literatures to investigate the hydrogeochemical characteristics and evolution mechanisms of formation water from different regional geological structure units in Qaidam Basin, China. The results indicated that TDS of formation water in Western (QW), Central (QC) and Northern (QN) units of Qaidam basin ranged from 173 to 290 g/L, 101 to 152 g/L and 32 to 73 g/L, respectively, which were several to dozens of times higher than those of seawater, but lower than those of intercrystalline brine and salt lake water. The enrichment of Ca, Li, B, Br and depletion of Mg and SO42- were observed in the formation water in comparison to seawater and salt lake water. Formation water especially in QC and QW was identified as typical dissolved brine of terrestrial rock origin, experiencing prolonged water-rock interactions. However, the time and degree of water-rock interaction and metamorphism differed regionally due to the sedimentary history and patterns of Qaidam Paleolake. Overall, the large paleolake deposits under the control of multiple tectonic movements laid the material foundation for the burial and generation of the formation water, and a variety of fluids and deep faults became the sources and migration channels for formation water. It mainly experienced two stages, including the sedimentary process of saline strata and the transformation in the later period.

Lithium and brine geochemistry in the Qianjiang Formation of the Jianghan Basin, central China

The Li-enriched oilfield brine is a very important lithium resource. It has gained much attention and become the target of active Li surveys with the growing global demand for Li. However, only little is known about their feature and nature. In the study, hydrochemical data from 155 oil wells tapping the Eocene to Lower Oligocene Qianjiang Formation of the Jianghan Basin, central China indicate that the brines are of the Na-Cl or Na-Ca-Cl type and are characterized by highly variable Li contents of 7.56 to 150 mg/L, with Mg/Li ratios less than 11.65. High Na/Cl and Cl/Br molar ratios indicate distinct contributions from halite dissolution. The Ca excess, Na deficit and Ca/Mg and Ca/Sr molar ratios in the brines imply multiple diagenetic processes, including halite dissolution, dolomitization, albitization and calcite or anhydrite cementation. The lithium contents of these brines have a weak relationship with the salinity and a negative correlation with Cl/Br ratios, possibly indicating that these Qianjiang oilfield brines have been diluted by secondary brines derived from halite dissolution. The spatial distribution patterns for Li and B concentrations of the brines are different from those for salinity and Br contents and show a geographic pattern, indicating that Li enrichment in the Qianjiang brines is likely connected with geothermal sources associated with volcanic activity.

A review of technologies for direct lithium extraction from low Li+ concentration aqueous solutions

Under the Paris Agreement, established by the United Nations Framework Convention on Climate Change, many countries have agreed to transition their energy sources and technologies to reduce greenhouse gas emissions to levels concordant with the 1.5°C warming goal. Lithium (Li) is critical to this transition due to its use in nuclear fusion as well as in rechargeable lithium-ion batteries used for energy storage for electric vehicles and renewable energy harvesting systems. As a result, the global demand for Li is expected to reach 5.11 Mt by 2050. At this consumption rate, the Li reserves on land are expected to be depleted by 2080. In addition to spodumene and lepidolite ores, Li is present in seawater, and salt-lake brines as dissolved Li+ ions. Li recovery from aqueous solutions such as these are a potential solution to limited terrestrial reserves. The present work reviews the advantages and challenges of a variety of technologies for Li recovery from aqueous solutions, including precipitants, solvent extractants, Li-ion sieves, Li-ion-imprinted membranes, battery-based electrochemical systems, and electro-membrane-based electrochemical systems. The techno-economic feasibility and key performance parameters of each technology, such as the Li+ capacity, selectivity, separation efficiency, recovery, regeneration, cyclical stability, thermal stability, environmental durability, product quality, extraction time, and energy consumption are highlighted when available. Excluding precipitation and solvent extraction, these technologies demonstrate a high potential for sustainable Li+ extraction from low Li+ concentration aqueous solutions or seawater. However, further research and development will be required to scale these technologies from benchtop experiments to industrial applications. The development of optimized materials and synthesis methods that improve the Li+ selectivity, separation efficiency, chemical stability, lifetime, and Li+ recovery should be prioritized. Additionally, techno-economic and life cycle analyses are needed for a more critical evaluation of these extraction technologies for large-scale Li production. Such assessments will further elucidate the climate impact, energy demand, capital costs, operational costs, productivity, potential return on investment, and other key feasibility factors. It is anticipated that this review will provide a solid foundation for future research commercialization efforts to sustainably meet the growing demand for Li as the world transitions to clean energy.