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Advanced lithium ion-sieves for sustainable lithium recovery from brines
Abstract
The escalating demand for lithium in electrochemical energy advice has stimulated growing focus on extracting Li from alternative sources such as brines. Lithium ion-sieves (LISs), comprising manganese-based and titanium-based LISs, emerging as a promising Li recovery technique, attributed to their exceptional capacity for lithium uptake, selectivity, and recyclability. However, practical implementation faces two critical challenges: the potential dissolution of specific ions (e.g., Mn3+ and Ti4+) and the severe particle aggregation during synthesis. In addition, coexisting ions like Mg2+ hinder the selective adsorption of Li+ due to their similar chemical properties. To meet these challenges, heteroatom doping is supposed to enhance the performance of LISs and diverse heteroatom doped LISs have been developed recently. Herein, this comprehensive review begins by delving into the fundamental aspects of LISs, including the LIS effect and types of LISs. Subsequently, adsorption behavior and practical application of modified LISs were discussed. Finally, prospects and research directions to solidify the role of LISs in pioneering environmentally friendly and economically viable lithium recovery methods are outlined.
... mg/g), and Ca 2+ (0-2.11 mg/g) [18]. After desorption, these impurities are carried into the resulting product solution. ...
... In general, brines exhibit a wide range of ions beyond those considered in this study, such as Fe, Zn, Mn, and others [19], which may also be present in solutions derived from DLE and subsequently in each post-treatment stage. In this study, the analysis focused on impurities like Na + , K + , Ca 2+ , and Mg 2+ , which are commonly carried over in direct lithium extraction processes, especially those based on adsorption and ion exchange [18]. Some challenges associated with feeding real brines include the presence of organic matter or other compounds such as Fe 2+ , as seen in solutions obtained from the recovery of spent-Li batteries [51]. ...
... Elements like sulfate and iron may form insoluble compounds, impacting the purity of Li 2 CO 3 . However, the concentrations of these impurities after DLE are relatively low, suggesting that their effects could be considered negligible in real scenarios [18,19]. ...
Direct lithium extraction (DLE) is emerging as a promising alternative to brine extraction although it requires further processing to obtain high-quality products suitable for various applications. This study focused on developing a process to concentrate and purify complex LiCl solutions obtained through direct lithium extraction (DLE). Two different chemical compositions of complex LiCl solutions were used, dividing the study into three stages. In the first part, lithium was concentrated to 1% by mass by evaporation. In the second, electrodialysis was used to alkalinize the LiCl solution and remove magnesium and calcium impurities under different current densities. The best results obtained were magnesium and calcium removals of 99.8% and 98.0%, respectively, and lithium recoveries of 99% and 96%. In the third stage, the selectivity of two different commercial cationic membranes (Nafion 117 and Neosepta CMS) was evaluated to separate Li⁺, K⁺, and Na⁺ cations under different current densities and volumetric flow rates. The Neosepta CMS membrane demonstrated higher lithium recovery. This study evaluated the quality of the purified lithium-rich solution and its potential use both in the production of Li2CO3 as well as in the electrochemical production of LiOH.
... It can complicate the separation and purification of recovered lithium and also result in the formation of organic waste which may require special disposal or treatment methods increasing the environmental burden of the process [26]. The synthesis and application of highly selective inorganic sorbents for lithium is a current scientific direction [ [27], [28]]. ...
... This selectivity is due to the large ionic radii of ions such as K + (0.138 nm), Na + (0.102 nm) and Ca 2+ (0.100 nm), in contrast to Li+ (0.074 nm), which makes them unable to cross narrow channels [39]. Although Mg 2+ (0.072 nm) has a similar ionic radius to Li + , its significantly higher free energy of hydration compared to Li prevents its dehydration, thereby limiting its access to exchange sites [ [28], [40]]. ...
The article presents the results of the study for the synthesized manganese dioxide sorbent after its saturation with lithium from brine. The sorbent was previously prepared. For this purpose the mixture of manganese oxide compounds was kept with lithium hydroxide in a wet state at 125 °C, calcinated at 450 °C and then the precursor was treated with dilute hydrochloric acid. The process intended to saturate the sorbent with lithium was performed by putting it in contact with a lithium-containing brine with a pH of 8.77 at T = 40°C for 24 hours in four cycles. The sorbent after saturation was studied using X-ray phase and thermal analysis methods. X-ray phase analysis showed that lithium-containing phases are represented by such compounds as Li(Li0.17Mn0.83)2O4 and Li0.78Mn1.88O4. The results of thermal analysis show the possibility of phases to be in the sorbent after saturation LiMn2O4 and Li1,3Mn2O4 phases. The study results showed that ion-exchange interaction takes place between the lithium-ion from the brine and the proton from the manganese-oxide spinel composition to a greater extent during sorption. Besides, the redox nature of the interaction is present during the sorption of lithium. All lithium intercalation reactions proceed topotactically without significant changes in the main structure of the original sorbent.
Lithium recovery from brines (oilfield brines, geothermal waters, mine tailings) is reported as a sustainable method of lithium production. Mn-based adsorbents offer a high sorption capacity hence are often applied for lithium harvesting. In this study two Mn-based adsorbents were prepared via solid state reactions. The morphology of materials were evaluated with a scanning electron microscopy (SEM) confirming the high surface area. After activation the sorbents were contacted with a model brine to test sorption kinetics. Three different kinetic models including the pseudo-first order rate equation, the pseudo-second order rate equation and logistic model were fitted to the experimental data. The results indicate that experiments are well described by the pseudo-second order rate equation. Conditions for sorption to occur are favorable: sorbents reach a high sorption capacity of about 10-12 mg/g in a short time (less than 2 hour). Further research should focus on optimization of sorption conditions (pH, temperature, sorbent regeneration).
Molecular hydrogen (H2) represents a sustainable and environmentally benign energy resource. Of the various methodologies that have been developed for H2 production, water electrolysis has garnered particular attention due to...
The demand for lithium extraction from salt-lake brines is increasing to address the lithium supply shortage. Nanofiltration separation technology with high Mg²⁺/Li⁺ separation efficiency has shown great potential for lithium extraction. However, it usually requires diluting the brine with a large quantity of freshwater and only yields Li⁺-enriched solution. Inspired by the process of selective ion uptake and salt secretion in mangroves, we report here the direct extraction of lithium from salt-lake brines by utilizing the synergistic effect of ion separation membrane and solar-driven evaporator. The ion separation membrane-based solar evaporator is a multilayer structure consisting of an upper photothermal layer to evaporate water, a hydrophilic porous membrane in the middle to generate capillary pressure as the driving force for water transport, and an ultrathin ion separation membrane at the bottom to allow Li⁺ to pass through and block other multivalent ions. This process exhibits excellent lithium extraction capability. When treating artificial salt-lake brine with salt concentration as high as 348.4 g L⁻¹, the Mg²⁺/Li⁺ ratio is reduced by 66 times (from 19.8 to 0.3). This research combines ion separation with solar-driven evaporation to directly obtain LiCl powder, providing an efficient and sustainable approach for lithium extraction.
Evaporative technology for lithium mining from salt-lakes exacerbates freshwater scarcity and wetland destruction, and suffers from protracted production cycles. Electrodialysis (ED) offers an environmentally benign alternative for continuous lithium extraction and is amenable to renewable energy usage. Salt-lake brines, however, are hypersaline multicomponent mixtures, and the impact of the complex brine–membrane interactions remains poorly understood. Here, we quantify the influence of the solution composition, salinity, and acidity on the counterion selectivity and thermodynamic efficiency of electrodialysis, leveraging 1250 original measurements with salt-lake brines that span four feed salinities, three pH levels, and five current densities. Our experiments reveal that commonly used binary cation solutions, which neglect Na+ and K+ transport, may overestimate the Li+/Mg2+ selectivity by 250% and underpredict the specific energy consumption (SEC) by a factor of 54.8. As a result of the hypersaline conditions, exposure to salt-lake brine weakens the efficacy of Donnan exclusion, amplifying Mg2+ leakage. Higher current densities enhance the Donnan potential across the solution-membrane interface and ameliorate the selectivity degradation with hypersaline brines. However, a steep trade-off between counterion selectivity and thermodynamic efficiency governs ED’s performance: a 6.25 times enhancement in Li+/Mg2+ selectivity is accompanied by a 71.6% increase in the SEC. Lastly, our analysis suggests that an industrial-scale ED module can meet existing salt-lake production capacities, while being powered by a photovoltaic farm that utilizes <1% of the salt-flat area.
Evaporitic technology for lithium mining from brines has been questioned for its intensive water use, protracted duration and exclusive application to continental brines. In this Review, we analyse the environmental impacts of evaporitic and alternative technologies, collectively known as direct lithium extraction (DLE), for lithium mining, focusing on requirements for fresh water, chemicals, energy consumption and waste generation, including spent brines. DLE technologies aim to tackle the environmental and techno-economic shortcomings of current practice by avoiding brine evaporation. A selection of DLE technologies has achieved Li + recovery above 95%, Li + /Mg 2+ separation above 100, and zero chemical approaches. Conversely, only 30% of DLE test experiments were performed on real brines, and thus the effect of multivalent ions or large Na + /Li + concentration differences on performance indicators is often not evaluated. Some DLE technologies involve brine pH changes or brine heating up to 80 o C for improved Li + recovery, which require energy, fresh water and chemicals that must be considered during environmental impact assessments. Future research should focus on performing tests on real brines and achieving competitiveness in several performance indicators simultaneously. The environmental impact of DLE should be assessed from brine pumping to the production of the pure solid lithium product. Sections
H2TiO3 (HTO) is considered to be one of the most promising adsorbents for lithium recovery from aqueous lithium resources duo to its highest theoretical adsorption capacity. However, its actual adsorption capacity is much lower owing to its unknown structure and incomplete leaching of lithium. After Al is doped into H2TiO3 (HTO-Al), the adsorption capacity of HTO-Al is 32.12 mg g-1 and the dissolution of Ti is 2.53%. HTO-Al has good adsorption selectivity, and all the separation factors α are ≫1. Furthermore, HTO-Al also exhibits good cyclic stability and solubility resistance. After 5 cycles, the adsorption capacity remains 29.3 mg g-1 and the dissolution rate is 1.7%. Therefore, HTO-Al has potential application value for recovering Li+ from aqueous lithium resources.
The H1.6Mn1.6O4 (HMO) derived from Li1.6Mn1.6O4 (LMO) has been aroused enormously attention due to high adsorption capacity. Through surface trace doping of F and S (LMO-R, R = F, S), the cycling stabilities and adsorption abilities of Li1.6Mn1.6O4 are improved. The adsorption uptakes are increased from 26.1 mg/g (before doping) to 33.4 and 27.9 mg/g at Li⁺ concentration of 12 mmol/L, respectively. In addition, first-principles calculations further confirm that F and S substitutes for O at 32e sites, leading to an improvement of the Li⁺ uptake rate. The Li⁺ adsorption capacities in the cycling process are enhanced by F and S doped, which may result from improving the charge density and offering more charge carriers that can participate in the ad/desorption reaction. The effect of the F and S substitution on adsorption capacity is discussed.
With the large-scale use of lithium-ion batteries, the global demand for lithium resources has increased dramatically. It is essential to extract lithium resources from liquid lithium sources such as brine and seawater, as well as recycled waste lithium-ion batteries. Among various liquid lithium extraction technologies, lithium ion-sieve (LIS) adsorption is considered to be the most promising method for its low energy consumption and environment-friendly. This method has advantages of excellent lithium uptake capacity, high selective, and good regeneration performance. In this review, we summarized the development of lithium manganese oxides (LMO)-type LIS, including the chemical structure, lithium intercalation/de-intercalation mechanism, preparation methods and forming technology of this material. The problems in the industrial application of ion-sieves are put forward, and the future research directions are prospected.
The currently commercialized lithium‐ion batteries have allowed for the creation of practical electric vehicles, simultaneously satisfying many stringent milestones in energy density, lifetime, safety, power, and cost requirements of the electric vehicle economy. The next wave of consumer electric vehicles is just around the corner. Although widely adopted in the vehicle market, lithium‐ion batteries still require further development to sustain their dominating roles among competitors. In this review, the authors survey the state‐of‐the‐art active electrode materials and cell chemistries for automotive batteries. The performance, production, and cost are included. The advances and challenges in the lithium‐ion battery economy from the material design to the cell and the battery packs fitting the rapid developing automotive market are discussed in detail. Also, new technologies of promising battery chemistries are comprehensively evaluated for their potential to satisfy the targets of future electric vehicles.
The increasing adoption of lithium in clean energy technologies has promoted significant development of novel and environmentally sustainable techniques for lithium extraction from secondary sources. In this review, we evaluate seawater and geothermal brines as potential secondary lithium resources for supplementing the rising demand. The review examines relevant literature to understand key aspects pertaining to lithium extraction from these systems in which the fundamental chemistry, the efficacy of different potential extraction techniques, and the associated impacts of each technique are critically reviewed. The extensive research in conventional closed basin brines is utilized as a baseline to demonstrate the current research progress, providing guidelines for future research direction in lithium extraction from seawater and geothermal brines. Based on the literature, it is suggested that sorption and ion-exchange will have high potential for prospective lithium extraction from aqueous resources like salars, seawater, and geothermal brines, and that the integration of activated carbon materials or microorganisms with these techniques will enhance the selectivity of lithium extraction from aqueous resources.
Increasing demand for lithium is leading to a rising focus on alternative, non-conventional lithium sources. These include geothermal brines, among others. The geothermal brines of the Upper Rhine Graben are characterized by comparatively high lithium concentrations of up to 200 mg L− 1. To exploit this untapped potential, various direct lithium extraction (DLE) techniques can be used including adsorption and ion exchange.
Several laboratory experiments on lithium extraction using inorganic sorbents such as lithium‐manganese oxides (LMO), lithium‐titanium oxides (LTO) and lithium‐aluminum-layered double hydroxide chloride (LDH) have been conducted in the past. Based on the promising results, various research projects are currently working on the development and implementation of the first pilot plants on existing geothermal sites.
Before lithium extraction from geothermal brines can be commercialized, not only the sustainability of the resource must be investigated, but also the DLE process must be adapted to the respective site conditions. Finally, improved sorbent performance will be the main driver for future cost reductions and enhanced economics in lithium extraction from geothermal brines.
Great progresses have been made in recovering valuable metals or regenerating materials from spent lithium-ion batteries (LIBs), but how to treat the spent electrolyte and recover its valuable components economically are still a bottleneck. In this study, the volatile organic solvents (dimethyl carbonate (DMC) and diethyl carbonate (DEC)) in spent electrolyte were recycled through vacuum distillation based on thermodynamic analysis and reused for LIBs. The recovery efficiencies of DMC and DEC reach almost 100% and 79.40%, respectively, under the distillation temperature of 130 °C for 120 min. The prepared electrolyte by recovered DMC and DEC shows high discharge capacity and good cycle performance (discharge capacity retention is over 99% after 400 cycles at 1C) by Li/graphite battery. Moreover, lithium left in non-volatile components (ethylene carbonate (EC)) was recovered as lithium carbonate (purity is 92.45%) with a recovery efficiency of 86.93%. The proposed process sheds light on the comprehensive recycling of electrolyte from spent LIBs.
Recovering lithium from lithium batteries (LIBs) is a promising approach for sustainable ternary lithium battery (T-LIB) development. Current lithium recovery methods from spent T-LIBs mainly concentrated on chemical leaching methods. However, chemical leaching relying on the additional acid seriously threatens the global environment and nonselective leaching also leads to low Li recovery purity. Here, we first reported a direct electro-oxidation method for lithium leaching from spent T-LIBs (Li0.8Ni0.6Co0.2Mn0.2O2); 95.02% of Li in the spent T-LIBs was leached under 2.5 V in 3 h. Meanwhile, nearly 100% Li recovery purity was also achieved, attributed to no other metal leaching and additional agents. We also clarified the relationship between lithium leaching and other metals during the electro-oxidation of spent T-LIBs. Under the optimized voltage, Ni and O maintain the electroneutrality in the structure assisting Li leaching, while Co and Mn maintain their valence states. A direct electro-oxidation Li leaching approach achieves high Li recovery purity and meanwhile overcomes the secondary pollution problem.
It is important to develop methods for efficient extraction of lithium from salt lake brine. However, the traditional lithium-extraction technology has various limitations, which make it difficult to increase its efficiency. Hence, it is highly important to explore new processes for lithium extraction. This paper systematically reviews the recent research on various coupled and tandem lithium-extraction technologies based on traditional lithium-extraction technology for extracting lithium from salt lake brine. When different technologies are coupled, their advantages aggregate, while their disadvantages become weaker, which, in turn, improves the lithium-extraction efficiency and makes the whole process simpler and environmentally friendly, with reduced energy consumption. For emerging coupling/tandem processes, the characteristics, applicability, and energy consumption of each method are analyzed based on the principle, characteristics, and performance of each technology. This review also discusses the direction that the future development of the process should take, according to the current development level of the process. Most of the discussed methods have completed laboratory-scale testing. Hence, future research should focus on pilot-scale development and optimization of the parameters and process involved. The cross-fusion and synergy of different methods provide ideas and references for better development and application of lithium-extraction processes.
Herein, sol-gel-synthesized α-Li2TiO3 was evaluated as a new promising anode material for lithium-ion batteries. The results show ultrastable release of discharge capacity within the range of 290-350 mA h g-1 in 400 cycles. Decent rate performances were also observed. A capacity of ca. 113 mA h g-1 was retained at a current density of 3 C. A 2 × 2 × 1 supercell of the lowest energy ordering structure was used in density functional theory simulations. The calculations show that in the intercalation process, Li+ preferentially enters the tetrahedral voids, leading to the activation of lithium-ion diffusion on the a-b plane with a minimal energy barrier of 0.06 eV (compared with 0.82 eV for the fully charged state). The activation of cation mobility at Li+ intercalation and insulator-conductor transition both contribute significantly to the ultrastability of the material. However, Li+ propagation along the c-axis is highly limited during the whole intercalation process. The enumeration of all the ordering structures on the tetrahedral sites shows two intermediate phases, α-Li2.25TiO3 and α-Li3.0TiO3, as observed from the formation energy convex hull.
Extraction of lithium from liquid lithium resources has become a popular research field, among which H2TiO3 material has great application potential. In this work, we further explored the correlation that the hydrophilicity of H2TiO3 with its adsorption performance based on the existing work. The double surfactants method was used to regulate the morphology and hydrophilic functional groups of the surface to regulate the material hydrophilia and prepare nano-sized lithium ion sieve. The effect of surfactant and preparation method on the hydrophilicity and adsorption properties of the materials were investigated. The results show that the synthesized lithium ion sieve H2TiO3-4 (HTO-4) has excellent hydrophilicity and adsorption performance reflected with the maximum adsorption capacity of 56.03 mg·g⁻¹. Meanwhile, the adsorption capacity loss of the material is only 3.8% after five cycles, which shows a satisfactory cyclic stability.
In this work, the magnetically recyclable lithium manganese oxide ion sieves (H1.6(AlxMn1-x)1.6FeyO4, HMO-x-y) with enhanced Li+ adsorption capability was synthesized by Al-Fe co-doping via hydrothermal reactions. XRD characterization showed that...
Lithium manganese oxide ion sieves (LMO-type) have excellent application prospects for extraction of lithium from brine due to their high adsorption capacities and superior selectivities. However, the dissolution loss of Mn affects their structural stability, and limits their industrial application. In this study, the zirconium-coated lithium ion sieve precursor LMZO was prepared by coating zirconium oxide into Li1.6Mn1.6O4 and performing solid-phase combustion. The results revealed that after acid leaching, the spinel structure and porous morphology of LMZO were maintained, which is beneficial for subsequent Li⁺ adsorption. The dissolution loss rate of Mn²⁺ decreased from 0.89% to 0.349% after coating, which was superior to that of pristine or coated Li1.6Mn1.6O4 materials previously reported. The lithium adsorption capacity of the zirconium-coated lithium ion sieve HMZO from Qinghai Kunty salt lake brine containing multiple coexisting ions was maintained at 25.96 mg/g at a Mg²⁺/Li⁺ concentration ratio of as high as 70, indicating that HMZO could be directly applied to highly saline brines. After 15 adsorption and desorption cycles, HMZO maintained a low dissolution loss of Mn and a large lithium adsorption capacity. This conclusion showed that HMZO has stable structure and excellent industrial application value. The Mn valence was higher in HMZO because the coating slowed the dissolution of Mn³⁺ and prevented dissolved Mn²⁺ from entering the solution; thus, the dissolution loss of Mn from HMZO was low. The adsorption of Li⁺ conformed to the pseudo-second-order kinetics model, indicating a Li⁺-H⁺ ion exchange mechanism.
The Dead Sea, a live pool of minerals and elements, holds ~9% of the worlds' known lithium reserves. However, the low lithium concentrations (30–40 mg/L) in the End Brine and the high divalent to lithium ratio (Mg+2 + Ca+2 to Li+) were obstacles that must be overcomed to extract the lithium. In our previous work, lithium concentrations in the Dead Sea End Brine were enriched by chemical precipitation up to 1700 mg/kg in the produced solid precipitate. The obtained precipitate was decomposed by double distilled water and about 66% of lithium was leached producing an environmental liquor containing an elevated concentration of lithium. A sequential ion exchange technique was used to achieve selective lithium recovery in this study. The ability of the UBK 10 strong acid‐type cation exchange resin (Na type) to remove lithium from simulated and environmental lithium‐bearing solutions was investigated. Because of the complex matrix comprising components that may compete with lithium adsorption, a greater quantity of adsorbent was required to achieve the equilibrium state for the environmental solution (7 grams) compared to (3.6 grams) for the simulated solution. For both lithium‐bearing solutions, the kinetics investigation revealed a pseudo‐second‐order tendency. The interfering capacity was determined to be 0.405, confirming the UBK 10 challenge to selective lithium adsorption. The divalent to lithium ratio was decreased by more than 50 times, yielding encouraging findings for extracting lithium from the low lithium ‐ high divalent to lithium sophisticated Dead Sea End Brines. This article is protected by copyright. All rights reserved.
A surge of interest has been attracted by Li1.6Mn1.6O4-type adsorbent for collecting lithium resources from salt-lake brines due to its excellent selectivity, high theorical adsorption capacity up to 72. 3 mg g⁻¹ and low cost. However, its large-scale practical application is limited because of its bone element Mn dissolution during the cycled desorption process. Herein, F and Al co-modifying technique, an efficient method for stabilizing its spinel structure or forming protective coating, was employed to improve the application performances of Li1.6Mn1.6O4-type adsorbent prepared by sol-gel method. Based on the various characterization results, the co-modification not only leads to the formation of fluoride-rich coating and the substitution of Mn³⁺ by Al³⁺, but also generates the active adsorbents with abundant nano-islands. DFT calculations revealed that the coating layer is indeed AlF3 rather than LiF. In addition, in-situ high-temperature XRD tests demonstrates that the co-modification can significantly enhance the heat resistance and structural stability of the material. As-prepared adsorbent exhibits greatly improved Li adsorption capacity (increased from 28.5 to 33.7 mg g⁻¹), lower Mn loss rate (decreased from 2.1 to 1.8%), enhanced cycling stability and good adsorption selectivity in the Qarhan brine containing Na⁺, K⁺, Ca²⁺, Mg²⁺, which is very significant and important for effectively removing lithium from low-grade brines.
Spinel-type lithium ion sieves exhibit many advantages. We report a gallium ion-doped precursor LiGa0.1Mn1.9O4 prepared by co-precipitation and hydrothermal method. The optimal synthetic parameters were determined by the orthogonal design experiments. The precursor was then transformed into the corresponding ion sieve HGa0.1Mn1.9O4 by pickling. The dissolution loss of Mn³⁺ for HGMO (4.65%) is less than that of the pristine ion sieve without Ga³⁺ doping (6.59%), which proves that the doped Ga³⁺ inhibits the dissolution loss effect. The equilibrium adsorption capacity Qe of HGMO is 25.30 mg∙g⁻¹ and the adsorption curve of HGMO for Li⁺ fits well with the pseudo-second-order kinetic model, indicating that the adsorption process is chemical adsorption. The adsorption isotherm conforms to the Langmuir model, and the adsorption process is monolayer adsorption. By the analysis of the adsorption enthalpy change (∆H), Gibbs free energy (∆G) and entropy (∆S) change of HGMO at different temperatures, the adsorption process of HGMO for Li⁺ was confirmed as endothermic and spontaneous.
Geothermal power plants produce large amounts of high-temperature fluids from variable depths. These fluids can be enriched in lithium to up to 240 mg/L, rendering them an exploitable resource, not yet processed at industrial scale. The pressure on Li demand is expected to increase in the future, making the technical degradability of new Li resources indispensable. We examine Li-extraction methods from aqueous solutions systematically, dealing with evaporation, direct precipitation, membrane-related processes, solvent extraction, sorption, and ion exchange. Sorption and ion-exchange techniques are regarded to be the most promising methods with a high potential for the feasible lithium extraction. Therefore, Li sorption on different inorganic sorbents, in particular for the implementation into operating geothermal power plants, is evaluated. Inorganic sorbents, such as lithium–manganese oxide, titanium oxide, aluminum hydroxide, iron phosphate, clay minerals, and zeolite group minerals besides other sorbents, e.g. zirconium phosphate, tin antimonate, antimony oxide, tantalum oxide, and niobium oxide, are regarded. Promising inorganic sorbents for an environmentally friendly, efficient, and selective Li extraction are lithium–manganese oxide, iron phosphate, or zeolite. To evaluate the effectiveness of these sorbents to large-scale industrial Li2CO3 (or LiOH) production, we highlight their potential advantages and disadvantages in the application under geothermal operating conditions.
The demand for lithium has increased incredibly during the last decade as it has become the mainstream for the growth of industrial products; especially batteries for electric vehicles and electronic devices. Given the high demand for lithium, researchers are focusing on methods for extracting lithium from a variety of sources. Among different liquid lithium extraction methods, lithium ion-sieve technology (LIS) is an emerging recovery method with great advantages over other approaches. LIS adsorption is a promising method for Li extraction owing to its low energy consumption, high lithium uptake capacity, environmentally friendly nature and superior lithium selectivity properties. A variety of physical and chemical methods can be applied to extract lithium from brines and ores. The present work critically reviews recent developments in lithium extraction and recovery using LIS adsorbents and membranes from aqueous solutions such as brine, seawater, etc. The paper has been particularly categorized based on the structure of the adsorbents and the pros and cons of various LIS adsorbents. Furthermore, this work emphasizes recent achievements with regard to the stability challenges encountered with LIS adsorbents. The favorable progress along with comparable advantageous such as higher lithium selectivity, lower environmental challenges, and higher energy efficiency have made LIS one of the most promising methods for lithium extraction from aqueous media.
Lithium ion sieve (LIS) has attracted great attention due to its high adsorption selectivity towards Li⁺. Herein, a new type of Zr-doped Ti-LIS (HZrTO) was synthesized by a simple calcination method. The adsorption capacity increased from 56.3 mg g⁻¹ (before doping) to 93.2 mg g⁻¹ after doping in LiOH solution (lithium 1.8 g L⁻¹). The adsorption isotherm and adsorption kinetics of HZrTO accord with the Langmuir isotherm and the pseudo-second-order kinetic equation, respectively. Batch experiments showed that HZrTO has good stability and selectivity. In addition, HZrTO was granulated via epoxy resin (E-12), and the obtained granular adsorbent showed good adsorption capacity, excellent stability and high selectivity towards Li⁺.
Owing to the increasing global demand for lithium, extraction of lithium from salt lake brine water has received considerable attention. In this study, the magnesium doping to produce Li1.6MgxMn1.6-xO4 (LMMO) was designed to overcome the limitation caused by the loss of Mn due to dissolution. The chemical and morphological properties of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The XRD results confirmed that the crystal structure of Li1.6Mn1.6O4 was retained after Mg-doping. Scanning electron microscopy and energy-dispersive X-ray spectroscopy showed that LMMO has a flake-shaped structure and the Mg²⁺ ions were uniformly distributed in the precursor. The doping of Mg²⁺ led to the decrease of Mn³⁺ content in the precursor, improving its structural stability. The adsorption capacity of LMMO-6% was 35.6 mg g⁻¹, which was greater than that of the undoped sample (33.2 mg g⁻¹). After the tenth cycle, the dissolution loss of Mn in LMMO-6% was 0.55%, and it is smaller than that for lithium manganese oxide (0.94%). Results confirm that the structural stability was improved compared to undoped adsorbents. Moreover, batch adsorption experiments demonstrated the potential of the HMMO-6% adsorbent to be used for lithium adsorption from real salt lake brine.
Li1.6Mn1.6O4 (LMO) is deemed as the most promising candidate for Li⁺ extraction from brine. However, it suffers from structural collapses and capacity fading during lithium adsorption/desorption cycles. To solve this problem, an effortless one-step dry method was adopted to prepared surface-fluorinated Mn-based ion-sieve materials using NH4F at low temperatures. XRD, FIB-SEM, HRTEM, XPS, and chemical analyses were used to characterize the crystal structure, morphology, surface information, chemical composition, and adsorption properties of the materials. The surface-fluorinated LMO showed an adsorption capacity of up to 31.86 mg g⁻¹, a low dissolution loss ratio of Mn, and remarkable long cycle stability with a capacity retention rate of 91.29%. The main reason for the improved adsorption capacity was that the surface fluorination eroded the material outside and increased the specific surface area. Furthermore, the bond energy and structural stability of the material were enhanced by the F–Mn bond, which partially replaced the surface O–Mn bond. In addition, DFT simulation was theoretically performed to understand the improvement mechanism of the material properties by fluorination. These results provide insights into the surface fluoridation effect in the optimization of Mn-based adsorbents, and the proposed simple modification strategy has the potential to be applied to large-scale production.
The Li⁺ adsorption from aqueous solution by lithium-ion sieve has become one of the most promising methods due to the high efficiency and selectivity towards lithium ion (Li⁺). However, the industrial application of manganese oxide ion-sieve is limited due to its difficult separation and decrease of adsorption capacity resulting from manganese dissolution loss. In this paper, the magnetically recyclable Fe-doped manganese oxide lithium ion-sieves with spinel-structure were proposed and prepared from LiMn2-xFexO4 synthesized by solid state reaction method. The effects of calcination temperature, calcination time and Fe doping amounts on the phase compositions, dissolution loss and adsorption performance of lithium ion-sieve precursors were systematically studied, and the influences of solution pH value, initial Li⁺ concentration and adsorption temperature on the adsorption performance were investigated. The adsorption mechanism was further discovered through adsorption kinetics and thermodynamics. The results show that the adsorption capacity of lithium ion-sieves could reach to 34.8 mg·g–1 when the calcination temperature, time and Fe doping content were controlled at 450 °C, 6 h, and 0.05, respectively. The Mn dissolution loss was reduced to 0.51%, much lower than the undoped lithium ion-sieve (2.48%), which is attributed to the inhibition of disproportionation reaction with the increasing proportion of Mn⁴⁺ in the skeleton. The adsorption process conformed to the pseudo-second-order kinetics equation and Langmuir isothermal adsorption model. Furthermore, the recycling performance of Fe-doped lithium ion-sieve showed that the adsorption capacity could remain 22.5 mg·g–1 (about 70%) after five cycles, which is greater than that of undoped lithium ion-sieve (about 50%), and the recovery of lithium ion-sieve can be realized by magnetic separation in an applying magnetic field.
Manganese based ion-sieves, particularly Li1.6Mn1.6O4, can be used to recover Li⁺ from salt lakes due to their excellent adsorption and anti-dissolution properties. Generally, the element doping can only improve the adsorbent capacity or enhance the structural stabilities. In this work, the adsorption capacity of Li1.6Mn1.6O4 is improved from 33.4 to 40.9 mg/g (c(LiCl)=24 mmol/L) via trace surface doping of Al (LMO-Al), likely owing to the partial substitution of Mn’s 16d sites by Al³⁺. Furthermore, the dissolution of Mn in Li1.6Mn1.6O4 is reduced from 5.4% (before doping) to 2.1%, which may due to stronger Al³⁺ and O²⁻ chemical bond and improving the amounts of Mn⁴⁺. In addition, Al doping allowed for the reduction of the dissolution loss rate of Mn during cycling, which greatly increases the possibility in practical application.
Layered H2TiO3 has been studied as an ionic sieve material for the selective concentration of lithium from solutions. The accepted mechanism of lithium adsorption on H2TiO3 ion sieves is that it occurs via Li+-H+ ion exchange with no chemical bond breakage. However, in this work, we demonstrate that lithium adsorption on H2TiO3 occurs via O-H bond breakage and the formation of O-Li bonds, contrary to previously proposed mechanisms. Thermogravimetric analysis results show that the weight loss due to dehydroxylation decreases from 2.96 wt % to 0.8 wt % after lithium adsorption, indicating that surface hydroxyl groups break during lithium adsorption. Raman and Fourier transform infrared spectroscopy studies indicate that H2TiO3 contains isolated OH groups and hydrogen-bonded OH groups. Among these two hydroxyl groups, isolated OH groups present in the HTi2 layers are more actively involved in lithium adsorption than hydrogen-bonded OH groups. As a result, the actual adsorption capacity is limited by the number of isolated OH groups, whereas hydrogen-bonded OH groups involved are for stabilizing the layered structure. We also show that H2TiO3 contains a high concentration of stacking faults and structural disorders which play a crucial role in controlling lithium adsorption properties.
Li1.6Mn1.6O4 (LMO) is a dominant adsorbent for lithium recovery from solutions resulted from its high theoretical adsorption uptake and a low loss rate of Mn, which can potentially be further improved by trace doping. We achieve stable cycling and high adsorption capacity of Li1.6Mn1.6O4 from aqueous lithium resources through surface trace doping of Na (LMO-Na). The dissolution of Mn is reduced from 5.4% (before doping) to 4.4%, and the adsorption uptake is increased from 33.5 mg/g to 33.9 mg/g at Li⁺ concentration of 24 mmol/L. In addition, first-principles calculations further confirm that Na substitutes for Li at 16d sites, leading to an improvement of the Li⁺ uptake rate and stabilizing the Mn cations in the compound. With the help of Na doping, the undesired dissolution of Mn in the cycling process is inhibited, which may result from reducing the content of the low valent Mn³⁺ and improving the structural stability of the adsorbent. The effect of the Na substitution on adsorption capacity and structure stability is discussed.
Lithium rich spinel lithium manganese oxide (LMO) compounds are one kind of promising adsorbent for lithium recovery from brine due to their high capacity and low Mn dissolution, Li1.6Mn1.6O4 is the one of them. However, Mn3+ exists in the Li1.6Mn1.6O4 precursor due to incomplete reaction during syntheses, and the disproportionation reaction of Mn3+ inevitably results in Mn dissolution during lithium adsorption and desorption. The stable recycling and structure stability of Li1.6Mn1.6O4 was improved in aqueous lithium resources through K-gradient doping (LMO-K). The dissolution of Mn is reduced to 4.0% from 5.4% (before doping), and the adsorption capacity is keeping as high capacity (31.6 mg/g) at low Li+ concentration of 12 mmol/L. In addition, first-principles calculations further confirm that K substitutes for Li at 16d sites, leading to a stabilizing the Mn cations in the compound. With the help of K doping, the undesired dissolution of Mn in the cycle process is inhibited, which may be due to reduction the content of Mn3+ and improvement the structural stability of the adsorbent.
The increasing demand for smart devices and clean energy vehicles that use lithium-ion batteries has sparked a considerable interest in lithium, which is becoming a strategic element. Lithium deposits can be found in saline lacustrine environments or pegmatite hard-rocks that are located mainly in America (Argentina, Bolivia, Chile, USA, and Canada), Australia (Western Australia), and China. In this paper, we summarise the main approaches of lithium extraction from pegmatites. Well established processes such as calcination, roasting, chlorination, carbonate pressure leaching, caustic/acidic digestion and others are examined and discussed to reflect their significance to the modern lithium value chain. In addition, emerging processes that involve direct mechano-chemical activation, bioleaching, acidic or caustic leaching are evaluated and compared to proven approaches in terms of economical and environmental viability. This review indicates that while established processes are still appealing to the industry despite their excessive energy requirement, new processes may contribute significantly to modernising lithium extraction in the future.
Al-doped lithium manganese oxides Li1.6AlxMn1.6-xO4 were successfully prepared by sol–gel synthesis and solid state reactions. Protonated samples were obtained by further acid treatment. Experiments were performed to study the effects of physical properties including the Al³⁺ doping content x and calcination temperature for optimizing the synthesis of H1.6AlxMn1.6-xO4 ion-sieve pursing nice performance such as enlarging the adsorption capacity and minimizing dissolution loss of manganese. The characteristics of a series of Al-doped ion-sieve were studied by XRD, SEM and EDS. The crystal structure was kept well after Al doping from XRD analysis. SEM and EDS showed that Al was uniformly distributed in the sample. The valence state of Mn in Al-doped ion-sieve precursor was analyzed by XPS. Adsorption/desorption experiments were carried out to evaluate the amounts of lithium extraction, lithium adsorption capacity and the manganese and aluminum dissolution loss of the ion-sieve. The results showed that the Al-doped H1.6Mn1.6O4 ion-sieve exhibited higher absorption capacity (which approached 32.6 mg g⁻¹ while the undoped one reached only 27.6 mg g⁻¹). Furthermore, the dissolution loss of manganese and aluminum from the Al-doped ion-sieve were the most impressive among the ones. Importantly, the Al-doped ion-sieve still preserve a high adsorption capacity (26.8 mg g⁻¹) and pretty low manganese dissolution loss (1.92%) after performing up to 4 cycles of adsorption/desorption experiments, indicating an enhanced stability of the Al-doped H1.6Mn1.6O4 ion-sieve.
Lithium ion sieves (LIS) have gained great interest in lithium recovery. However, the synthesis of high stability, selectivity, and adsorption capacity of LIS is still a great challenge. Here, a general strategy combining electrospinning and calcination techniques is developed to fabricate a series of porous titanium-based LIS nanofibers. The porous structure created by calcination increases the exposure of the adsorption sites, which significantly accelerates the deintercalation and intercalation of Li⁺ from and into the vacancies in the framework. All of samples have good Li⁺ adsorption capacity and high selectivity for Li⁺. As a proof of concept, porous H4Ti5O12 nanofibers (P-HTO-NF) transformed from the electrospun porous Li4Ti5O12 nanofibers (P-LTO-NF) are systematically investigated in lithium recovery. P-HTO-NF possesses a superior adsorption capacity (59.1 mg/g), which is nearly close to the theoretical value (63.77 mg/g). The Freundlich isotherm model can well describe the adsorption isotherm data. The adsorption equilibrium can reach within 30 min (C0 = 300 mg/L, pH = 11, S/L = 60 mg/60 mL). The equilibrium distribution coefficient (Kd, mL/g) for Li ⁺ (232) is extremely higher than that for competing ions (1.41 for Na⁺, 1.17 for K⁺, 0.88 for Mg²⁺, 0.58 for Ca²⁺) (C0 = 40 mg/L for Li⁺, pH = 8), indicative of a highly selective recovery of lithium from brine water. The LIS show excellent stability with a low Ti dissolution and the adsorption capacity for Li⁺ remains 86.5% after 6 cycles. Our work provides a universal strategy for the synthesis of porous LIS.
Li1.6Mn1.6−xCrxO4 was synthesized by hydrothermal reaction followed by acid leaching to form lithium ion sieve. The structure, morphology and composition were examined using X-ray diffraction, SEM and EDS. The influences of Cr doping content and hydrothermal temperature on Li+ adsorption capacity and manganese dissolution ratio were investigated. The result indicates that Cr is incorporated into the spinel structure with cell contraction when x ≤ 0.08. Li1.6Mn1.6−xCrxO4 shows Li+ adsorption capacity of 31.67 mg/g and Mn dissolution ratio of 2.1% when x is 0.016 at 270 °C. After 20 cycles in salt lake brine, the Mn dissolution ratio and Li adsorption capacity is 0.35% and 25.5 mg/g, respectively. The Cr-doped ion-sieve shows improved adsorption capacity, retention and structural stability compared with the undoped lithium ion-sieve. The adsorption process for the Cr-doped ion-sieve follows a pseudo-second-order kinetic model.
Due to the abundant reserves and increasing demand, the extraction and separation of lithium from salt-lake brines have attracted great interest worldwide. This review aims to summarize the major developments in lithium recovery from brines, starting from an overview of lithium demand and consumption, available resources and processing methods, and challenges of processing brines, followed with the advancements in solvent extraction, ion-sieve adsorption, electrochemical approaches, and membrane technology, successively. The paper focuses on the principles, mechanisms, operations, and comparison of the various approaches. Other promising techniques, such as the modification of ion-sieves, rocking-chair batteries, and liquid-membrane electrodialysis, also are discussed in the depth of mechanisms. These processes present excellent performance in the separation of Li ⁺ /Mg ²⁺ or Li ⁺ /Na ⁺ . Finally, insights into the directions and prospects of lithium extraction from brines are presented. It can be concluded that only by integrating the advantages of various recent technologies will it be possible to develop an efficient, low cost, environmentally sustainable, and scalable process for lithium extraction from brines.
Titanium oxide lithium ion sieve (Ti-LIS)is regarded as the most promising adsorbent due to its highest theoretical lithium adsorption capacity and excellent stability among various other lithium ion sieves. A new kind of Ti-LIS precursor with Mo-doped was prepared by a facile calcination method. The related lithium ion sieve (Mo-Ti-0.15 (H))with a high O 2– content (61.58%)was obtained by acid pickling. Mo-Ti-0.15 (H)possesses a quite high adsorption capacity, up to 78 mg g ⁻¹ in LiOH solution (lithium 1.8 g L ⁻¹ )at room temperature, which is much higher than that of the other lithium ion sieves reported. In addition, the adsorption isotherm and kinetic of the Mo-Ti-0.15 (H)belong to the Langmuir isotherm and pseudo-second order kinetic equations. Finally, the Mo-Ti-0.15 (H)shows a good stability and excellent selectivity, which was demonstrated by batch experiments.
In this study, recovery of lithium in seawater using a titanium-intercalated lithium manganese oxide composite (LTMO) was investigated along with its adsorption capacity and durability. To minimize manganese dissolution during the extraction of Li⁺ by acidic treatment, a spinel type of LTMO was synthesized by the high-energy milling of a titania (TiO2), lithium carbonate (Li2CO3), and manganese carbonate (MnCO3) mixture and subsequent heat treatment. X-ray diffraction and thermogravimetric analyzer confirmed that Ti was well intercalated into the spinel structure of lithium manganese oxide (LMO). The effects of calcination temperature and Ti content on LTMO structure, lithium uptake, and adsorbent stability were investigated. Kinetic analysis showed that adsorption by LTMO followed pseudo-second-order kinetics, with a correlation coefficient in excess of 0.99. Adsorption by LTMO fitted the Langmuir isotherm well, with a correlation coefficient higher than 0.99, and LTMO exhibited higher theoretical maximum adsorption capacity than LMO (up to 21.9 mg g⁻¹ vs. 19.6 mg g⁻¹). In addition, LTMO showed high selectivity for lithium ions in the presence of competitive cations.
Iron-doped lithium titanium oxides were prepared via a solid-state reaction and transformed into lithium ion sieves by acid treatment. Scanning electron microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy showed that Fe³⁺ was doped into the Ti–O lattice and Ti–Fe–O bonds were formed. Iron-doping improved lithium ion adsorption from brines. The saturated adsorption capacity of the iron-doped ion sieves in brine (Li⁺ 1.56 g/L, pH = 8.8) was 34.8 mg/g. Lithium ion adsorption fitted pseudo-second-order kinetic and Langmuir equations, indicating that lithium ion adsorption on iron-doped lithium ion sieves was chemical and predominantly monolayer. In addition, the iron-doped ion sieves showed excellent selectivity for lithium ion and good recyclability. These iron-doped ion sieves therefore provide effective lithium adsorbents for practical applications. © 2018 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences
Selective-electrodialysis (S-ED) is a booming technology for recovering lithium from salt lake brine and (concentrated) seawater, especially from high Mg²⁺/Li⁺ ratio brines. The coexisting ions in the solutions containing lithium can make some impact on the ion fractionation of lithium and magnesium in high Mg²⁺/Li⁺ brines. The effect of the concentration of coexisting cations (Na⁺, K⁺) and anions (SO4²⁻, HCO3⁻) on the separation coefficient of magnesium and lithium (FMg-Li), recovery ratio of Li⁺ (RLi), current efficiency (η) and specific energy consumption (ESEC) was evaluated. The results show that an applied voltage of 6 V is more preferable for lithium ions recovery from high Mg²⁺/Li⁺ brines by S-ED. The separation of Mg²⁺/Li⁺ tends to unsatisfactory with increasing cation concentration (Na⁺, K⁺), and FMg-Li drops from 8.73 to 1.83 with the increase of Na⁺/Li⁺ from 1 to 5 and from 8.33 to 2.13 with the rise of K⁺/Li⁺ from 1 to 5. The strength of influence on the separation of Mg²⁺/Li⁺ is K⁺ > Na⁺, correlating with the order of their hydrated ion radiuses. However, FMg-Li rises from 7.99 to 14.66 with the increase of SO4²⁻, reversing with the influence of cations concentration. As for HCO3⁻, the variation tendency of FMg-Li is opposite to RLi, probably ascribing to the appearance of MgHCO3⁺. These observations showed that S-ED has a wide adaptability for the ion fractionation of magnesium and lithium from brines.
Monoclinic β-Li2TiO3 (LTO) is regarded as a lithium adsorbent precursor. In order to inhibit agglomeration during solid state reaction, C2H3LiO2·2H2O instead of Li2CO3 was firstly used as the lithium resource to synthesize LTO. Lithium ion sieve H2TiO3 (HTO) was then obtained by acid treatment of LTO. Physicochemical properties of obtained LTO and HTO were characterized via powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and particle size distribution analysis (PSD). Lithium adsorption selectivity and stability of prepared HTO for West Taijinar Salt Lake were investigated. Solid state reaction mechanism of C2H3LiO2·2H2O and TiO2 was investigated by TG-DTA analysis. Results show that melting of C2H3LiO2·2H2O (at 64.5 °C) during the early calcination stage could form liquid–solid phase and remarkably improve mixing of C2H3LiO2·2H2O and TiO2. Compared to Li2CO3 used as the lithium resource, huge heat and gases released during the reaction of dehydrated C2H3LiO2·2H2O and TiO2 (between 380 °C and 515 °C) accelerate the nucleation process and effectively inhibits agglomeration, which leads to a smaller particle size (∼70 nm). It is shown that lithium uptake and adsorption rate were improved because of easier mass transfer during the ion-exchange process. Lithium adsorption behavior could be well described by the Langmuir isotherm and pseudo-second-order kinetic model. Seperation factor α (Li/Mg) of obtained HTO in West Taijinar Salt Lake brine reached 5441.17, meaning remarkable lithium adsorption selectivity in real lake brine. Besides, adsorption uptake remained 24.5 mg/g after 5 cycles in West Taijinar Salt Lake brine, which indicates obtained HTO has good stability.
Li-excess cathode materials are expected to have great potential for applications in lithium-ion batteries for their high energy density. Besides the extensive studies on the anionic redox activity in them, their Li-ion diffusion properties have also attracted much interest. Using ab initio calculations, here we systematically explored Li diffusion properties in both stoichiometric and Li-excess phase of spinel lithium manganese oxide (LMO). Our results show that there is a kind of structure unit (six Mn forming a cation ring for Li-ion passing through during migration) to play as “gate sites”, and the Li-excess configuration can introduce two kinds of fast Li-ion migration channels to enhance the Li-ion diffusivity. The first kind of fast channels result from that the Li+ substitution of Mn3+ can decrease the Coulomb repulsion interactions between the cations at the gate site and the mobile Li-ion. The second kind of fast channels originate from that the excess Li can induce more gate sites with symmetrical distribution of Mn4+ surrounding the Li diffusion channel, which is proved to be able to enhance the Li-ion mobility. Interestingly, it is also found that in the slow Li diffusion channels for both stoichiometric and Li-excess LMO, a simultaneous polaron hopping process around the gate sites will be coupled to the Li migration process, which accounts for the high energy barriers of Li-ion diffusion.
Al-doped LiAlxMn2-xO4 ion-sieves were optimally synthesized with improved structural stability for Li⁺ adsorption through hydrothermal synthesis method. Firstly, several parameters including the Al³⁺ doping content x, hydrothermal temperature, hydrothermal treatment time and calcination temperature were investigated to optimize the synthesis of LiAlxMn2-xO4 ion-sieves for selecting unique spinel structure with low dissolution loss (R) for Li⁺ adsorption. Then, the pristine LiMn2O4 (LMO) and optimized LiAl0.1Mn1.9O4 (LAMO) ion-sieves were comparatively investigated from their microstructure and chemical state to Li⁺ adsorption performance. The desorption ratio of Li⁺, adsorption capacity (Q) and the dissolution losses (RMn²⁺ and RAl³⁺) of the ion-sieves were evaluated by adsorption-desorption experiments. It was found that the maximum equilibrium adsorption capacity QLAMO was 27.66 mg g⁻¹ and the desorption ratio of Li⁺ could reach 81.2% after 120 min. Meanwhile, RMn²⁺ and RAl³⁺ of LAMO ion-sieve were very low in the desorption process. Moreover, LAMO ion-sieve also shows excellent stability and repeatability that the LAMO could still maintain a high adsorption capacity (19.5 mg g⁻¹) with very low RMn²⁺ (3.71%) and negligible RAl³⁺ after repeating 5 times adsoprtion-desorption operation.
Ultrafine lithium titanate (Li2TiO3) powder was synthesized by hydrothermal method. The phase formation and transition condition among α, β, and γ-Li2TiO3 were discussed. XRD and ICP-AES showed the single α-phase was formed at 180 °C with 2 h hydrothermal reaction, and it transited into β-phase at 400 °C. SEM observation and EDS analysis confirmed the dissolution of TiO2 and the formation of α-Li2TiO3 proceeded simultaneously with preferable growth direction of (-133) lattice. During the phase transition, the powder maintained the small crystallite, which facilitated the fabrication of Li2TiO3 bulk with small grain size. After the Ar⁺ irradiation, the surface region to the depth of 3 μm of Li2TiO3 ceramic was affected, where the decrease of crystallization and disturbance of short-range order were confirmed by GIXRD and Raman spectroscopy. In spite of the structure change at the surface area, the ceramic bulk maintained the same.
Lithium-enriched monoclinic lithium metatitanate (β-Li2TiO3) with a high molar ratio of Li to Ti (2.11) was synthesized by a hydrothermal method. The related lithium ion-sieve (H2TiO3), obtained by acid pickling of Li2TiO3, with a specific surface area of 45.35 m2 g−1 and a pore volume of 0.166 cm3 g−1 possessed a maximum adsorption capacity of 76.7 mg g−1 in LiOH solution (∼2 g L−1 of Li+ ions) at 30 °C for 24 h, which was much higher than those reported for other lithium ion-sieves. Adsorption isotherms and kinetic analysis indicated that the adsorption of Li+ ions onto H2TiO3 followed the Langmuir isotherm model and a pseudo-second order kinetics equation. The adsorption mechanism showed that the improvement of lithium adsorption capacity was closely related to the free hydrogen formation of β-Li2TiO3 and HTi2 layer exposure of H2TiO3, suggesting a clear direction for designing the lithium ion-sieve with high performance.