Salt Lake Brine Research Articles

Porous organic polymer interlayers modulated nanofiltration membranes for ultra-permselective Li+ /Mg2+ separation

The ion-ion precise separation is of paramount importance but presents significant technical challenges. Achieving such an accurate separation utilizing nanofiltration (NF) membranes demands ion-selective channels with appropriate pore geometry structure and charge property. In this work, thinner polyamide (PA) NF membranes with narrower pore size distribution than conventional NF membranes were fabricated via the porous organic polymer (POP) interlayer-mediated interfacial polymerization. The dual-rigid-distorted POP interlayers were incorporated in situ onto the substrates through azo-coupling reactions. The POP interlayers exhibited a high-density adsorption capacity of amine monomers and acted as a space manipulator that regulated their diffusion behavior into the oil phase, enabling their reaction with the acyl chloride. The synergistic effects engendered a uniform PA active layer and impeded further growth of the membrane, compared with the typical PA membranes, facilitating the generation of a thin and a narrow pore size distribution PA active layer with a nanostripe surface. The prepared NF membranes showed an outstanding ion-ion separation factor of Li+/Mg2+ (up to 78.56), almost 18 times that of the pristine NF membrane (4.32), along with a two-fold increase in water permeance. Furthermore, the newly developed NF membranes demonstrate long-term stability under operational pressure, thus highlighting the promising potential of these NF membranes for extracting Li+ from salt-lake brines.

Extraction of Lithium From Salt Lake Brine with High Mg/Li Mass Ratio by N523-DIBK Extraction System

Extraction of Lithium From Salt Lake Brine with High Mg/Li Mass Ratio by N523-DIBK Extraction System

Binder-Free LiMn2 O4 Nanosheets on Carbon Cloth for Selective Lithium Extraction from Brine via Capacitive Deionization.

In this study, a three-step strategy including electrochemical cathode deposition, self-oxidation, and hydrothermal reaction is applied to prepare the LiMn2 O4 nanosheets on carbon cloth (LMOns@CC) as a binder-free cathode in a hybrid capacitive deionization (CDI) cell for selectively extracting lithium from salt-lake brine. The binder-free LMOns@CC electrodes are constructed from dozens of 2D LiMn2 O4 nanosheets on carbon cloth substrates, resulting in a uniform 2D array of highly ordered nanosheets with hierarchical nanostructure. The charge/discharge process of the LMOns@CC electrode demonstrates that visible redox peaks and high pseudocapacitive contribution rates endow the LMOns@CC cathode with a maximum Li+ ion electrosorption capacity of 4.71mmol g-1 at 1.2V. Moreover, the LMOns@CC electrode performs outstanding cycling stability with a high-capacity retention rate of 97.4% and a manganese mass dissolution rate of 0.35% over ten absorption-desorption cycles. The density functional theory (DFT) theoretical calculations verify that the Li+ selectivity of the LMOns@CC electrode is attributed to the greater adsorption energy of Li+ ions than other ions. Finally, the selective extraction performance of Li+ ions in natural Tibet salt lake brine reveals that the LMOns@CC has selectivity ( = 7.48) and excellent cycling stability (100 cycles), which would make it a candidate electrode for lithium extraction from salt lakes.

Fine-tuning polyamide nanofiltration membrane for ultrahigh separation selectivity of Mg2+ and Li+

The extraction of lithium resources from salt-lake brine has garnered increasing attention, and a critical challenge is to achieve an effective separation of Mg2+ and Li+. This study focuses on addressing this challenge using isophthaloyl chloride (IPC) in combination with trimesoyl chloride for completing interfacial polymerization (IP) with polyallylamine. The product is an unexpectedly highly permeable and permselective polyamide nanofiltration (NF) membrane that is effective for Mg2+/Li+ separation. Adjusting the acyl chloride density with IPC influenced the IP reaction progress, thereby yielding a polyamide layer with fine-tuned properties. Various characterization results demonstrated a significant difference in the positive chargeability between the NF membranes doped with IPC and the blank NF membrane without IPC, whereas other properties remained comparable. The optimal NF membrane prepared with a low IPC molar ratio of 33% exhibited highly positively charged and high permeability characteristics. Considering the remarkable advancements in separation performance and simplified fabrication process, a fine-tuned strategy for designing highly positively charged NF membranes holds great practical potential for the industrial development of lithium extraction from salt-lake brines.

Attack resistance mechanism, uniaxial compressive mechanical properties and meso-simulation of high-performance concrete exposed to brine in salt lake for 10 years

The study investigated the corrosion resistance, corrosion micro-mechanisms, and the uniaxial compression stress–strain constitutive relationship of high-performance concrete (HPC) specimens subjected to long-term brine corrosion in an underground salt lake environment (Xining, China), which possesses a salt content of 180894.5mg/L. A three-dimensional random aggregate concrete meso-model was established considering the mesostructural characteristics of concrete. The mechanical behavior of HPC was assessed using the LS-DYNA software platform. The findings indicated that both the compressive strength and the dynamic elastic modulus of HPC demonstrated a pattern of initial increase, followed by a decrease, with extended brine exposure. Nevertheless, after 10 years of exposure to salt lake brine, the compressive strength of the HPC samples was still considerably greater than their original strength, with minimal evident corrosion damage to the concrete. Physical and chemical corrosion products formed exclusively in the spherical pores created by the air-entraining agent within the shallow layer of HPC, without notable micro-cracks or spalling. The HPC specimens exposed to brine for ten years under uniaxial compression load exhibited typical characteristics of splitting failure. In addition, the results from the mesoscopic numerical simulations aligned well with the experimental findings. The study shows that the three-dimensional random aggregate concrete mesoscopic model can simulate the uniaxial compressive mechanical behavior of HPC specimens under long-term corrosion conditions.

Li+ Separation from Multi-Ionic Mixtures by Nanofiltration Membranes: Experiments and Modeling

Aqueous sources like salt lake brines and seawater are the most abundant source for lithium ions and might contribute to the growing demand for lithium for energy storage. By coupling with the increasingly relevant reverse osmosis systems, nanofiltration can provide a promising process alternative to conventional methods such as water evaporation and salt precipitation from ores or brines for this purpose. One possible model for nanofiltration is the solution-diffusion-electromigration model (SDEM). First, the model was parametrized by determining the permeances from simple electrolyte mixtures containing two salts. Then, the SDEM was used to predict the rejections of complex multi-electrolyte solutions that mimic seawater and reverse osmosis brine, without fitting additional parameters to experimental data of this complex mixture. This allowed predicting ion rejections satisfactorily. Negative rejections due to spontaneously generated electric fields in the membrane could also be qualitatively described. In summary, this SDEM modeling can provide an important contribution to the purification of Li+ from aqueous sources.

Sustainable Lithium Recovery from Hypersaline Salt-Lakes by Selective Electrodialysis: Transport and Thermodynamics.

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.

Lithium solvent extraction by a novel multiframe flat membrane contactor module

Comparing to conventional liquid–liquid extraction, membrane extraction is an efficient and environmentally friendly separation technique to recover lithium from the salt-lake brine. Development of suitable hydrophilic solvent resistant nanoporous membranes for membrane extraction has been based on bench-scale small module. Because module design has significant impact on the performance, this work reported a novel multiframe flat membrane contactor module (MFMC) for lithium extraction from synthetic brine. The hydrophilic poly (ethylene-co-vinyl alcohol)/sulfonated poly(etheretherketone) membrane supported with polypropylene nonwoven (EVAL/SPEEK-NW) was prepared for module evaluation. The membrane mass transfer coefficients km of 1.1 × 10-6 m/s was obtained by Wilson plot. The global mass transfer coefficient Ke increased from 4.5 × 10-7 m/s to 9.9 × 10-7 m/s following the flow velocity from 0.4 to 1.8 cm/s in membrane extraction. We further evaluated the characteristics of MFMC via height of transfer units (HTU) and module efficiency (ME). High module efficiency of 90% was obtained, demonstrating MFMC’s efficient flow distribution. HTU of 28 m was estimated and was expected to decrease to 3 m by optimizing thickness of gasket and spacer as well as membrane performance. The MFMC module effectively reduced the loss of tributyl phosphate (TBP) by 91% comparing to liquid–liquid extraction. The research presented herein provides a flat membrane module design for potential future application of membrane extraction in wide applications.

Supported ionic liquid membrane contactor with crown ether functionalized polyimide membrane for high-efficient Li+/Mg2+ selective separation

Worldwide demand for lithium is increasing rapidly. Implementing an efficient extraction for lithium from salt-lake brines with low concentration and high Mg/Li (m/m) ratio remains challenging. A supported ionic liquid membrane (PI@14C4-SILM) contactor was developed in this work using a crown ether functionalized polyimide membrane material (Poly(DAB14C4-6FDA)) as the support and tributyl phosphate (TBP) and (1-butyl-3-methylimidazolium bis-trifluoromethylsulfonimide salt) ([C4mim][NTf2]) mixture as the liquid phase for high-efficiency Li recovery. The results show that when the feed phase Mg/Li ratio is 35 and the stripping phase is 0.5 mol/L HCl, the Li+ penetration rate, initial flux and Li/Mg selectivity of PI@14C4-SILM contactor are 0.354 μm/s, 0.128 mol/m2·h and 19.1, respectively. Molecular dynamics (MD) simulation results show that Poly(DAB14C4-6FDA) and TBP have greater interaction with Li+ than other ions (Na, Mg, K). Meanwhile, the binding energies of Poly(DAB14C4-6FDA)-Li-NTf2 and TBP-Li-NTf2 were calculated by density functional theory (DFT), which were −163.26 and −182.1 kcal/mol, respectively. The higher binding energies of the complexes indicated that their structures were more stable. The mechanism of the PI@14C4-SILM contactor's excellent Li+ mass transfer performance may be the formation of a fast Li+ transfer channel between the solid phase containing the crown ether structure and the liquid mobile phase in the pore structure. Besides, the TBP·Li·NTf2 and TBP·H·NTf2 structures in the liquid membrane phase effectively maintained the cyclic operation of the SILM system. This study provides an effective solution for selective separation of Mg/Li and utilization of Li resources in salt lake water.

Bifunctional polyhedral oligomeric silsesquioxane engineered polyamide membrane for efficient Li+/Mg2+ separation

Nanofiltration membrane technology holds great promise in extracting lithium (Li) from salt-lake brines. However, designing nanofiltration membranes with both high water permeance and ion selectivity remains a grand challenge. Here, amino-functionalized polyhedral oligomeric silsesquioxane (8NH2-POSS) nanocage is designed as a bifunctional molecular filler into polyamide (PA) layer during the interfacial polymerization of polyethyleneimine (PEI) and trimesoyl chloride (TMC). The 8NH2-POSS not only provides abundant amino groups to increase the membrane electropositivity from +4.5 mV to +33.2 mV (pH = 6.0), but also enlarges the pore size of PA matrix and constructs additional water channels to facilitate water transport. The optimal POSS-PA membrane has a rejection rate of 98.1 % to 1 g/L MgCl2, a pure water permeance of 12.0 L m-2h−1 bar−1 and an exceptional separation factor (SLi,Mg) of 13.9 at an ultralow Li+/Mg2+ mass ratio of 1:150, surpassing the benchmark PA membranes.

Positively charged thin-film composite hollow fiber nanofiltration membrane via interfacial polymerization and branch polyethyleneimine modification for Mg2+/Li+ separation

It is a vital technical challenge to extract lithium from salt-lake brine which has very high Mg2+ / Li+ mass ratio via green and low-cost methods, as these two cations have quite similar ionic hydration radius. Positively charged nanofiltration membranes can separate Li+ and Mg2+ through Donnan exclusion. In this work, a kind of hollow fiber nanofiltration membrane with positively charged skin layer was successfully fabricated via interfacial polymerization followed by a surface modification with branched polyethyleneimine (BPEI). The resultant membrane has a large number of amine groups, and thus shows positively charged surface with high rejection for divalent cation ions via Donnan exclusion. This gives it very high selectivity for the separation of Li+ ions from salt-lake brine. Under optimized conditions, it achieves a water permeance of up to 126.2 L m-2 h-1 MPa−1 at a transmembrane pressure difference of 4 bar, and a MgCl2 rejection of 94.6% with 2000 mg L-1 aqueous MgCl2 solution as feed. Meanwhile, it achieves a Mg2+ / Li+ selectivity of nearly 24 for MgCl2 and LiCl salt mixture solution with an overall concentration of 2000 mg L-1 and a Mg2+ / Li+ mass ratio of 150 : 1 as feed, which is high as compared with most of the literature, demonstrating its potential in the practical application of Mg2+ and Li+ separation.

Forsterite refractory preparation using magnesium resources from salt lake brines

In this study, combined precipitants of sodium metasilicate and sodium hydroxide were used for effectively separating lithium (Li) from magnesium (Mg) in salt lake brine and meanwhile generating magnesium precipitates with high MgO/SiO2 molar ratios to produce high-performance refractory materials. When the mole of combined precipitant was 1.0, Li/Mg precipitation separation can be achieved with Mg precipitation yield of above 99.5% and Li precipitation yield of approximately 5%. The MgO/SiO2 molar ratio in magnesium precipitates can be enhanced by adjusting the mole fraction of sodium hydroxide (NaOH) in the combined precipitant. Under the condition of a NaOH mole fraction was 40%, sintering temperature of 1350 ℃, and sintering time of 180 min, the prepared refractory material comprised of mainly forsterite phase and showed excellent properties of the refractoriness of 1780 ℃, bulk density of 2.21 g/cm3, and compressive strength of 118.11 MPa. This study could provide a promising guide for facile production of value-added forsterite refractory materials using magnesium resources in salt lake brine.

Comparison of the Mg2+-Li+ Separation of Different Nanofiltration Membranes.

Nanofiltration application for the separation of Mg2+-Li+ from salt-lake brines was attempted in the present work. Four different nanofiltration membranes identified in the manuscript as DL, DK, NF-270, and NF-90 were used to treat salt brine with a magnesium to lithium ratio (MLR) of 61, additionally contaminated by the other ions such as Na+, K+, Ca2+, etc. The effect of the dilution factor, operating pressure, circulation rate, and feed pH were assessed to identify the optimal operating conditions for each membrane based on the retention efficiency of each ion. The results showed an insignificant effect of Ca2+ on the retention performance of Mg2+-Li+. Na+ and K+ had a smaller hydration radius and larger diffusion coefficient, which competed with Li+ and altered the separation of Mg2+-Li+. Under the optimal conditions (dilution factor: 40; operating pressure: 1.2 MPa; circulation flow rate: 500 L/h; pH: 7), the retention efficiency of lithium was as low as 5.17%, separation factor (SF) was as low as 0.074, and the MLR in the permeate reduced to 0.088.

Doping engineering of lithium-aluminum layered double hydroxides for high-efficiency lithium extraction from salt lake brines

Doping engineering of lithium-aluminum layered double hydroxides for high-efficiency lithium extraction from salt lake brines

Gelatin aerogel with good mechanical properties and adjustable physical properties for boron adsorption from salt lake brines: An optimized process

A composite aerogel with good mechanical properties and adjustable physical properties was synthesized by a sol-gel technique on the base of gelatin for the boron adsorption from water solution. The adsorption key variables, for instance, initial boron concentration (C0) (900–1100 mg/L), the contact time (t) (8–9 h), and pH (9–11), were optimized using central composite design to obtain improved boron adsorption performance of epichlorohydrin-modified gelatin (EMG)/N-methyl-d-glutamine (NMDG) aerogel loaded with hydroxylated carbon nanotubes (EMG@NMDG). The adsorption followed the pseudo-second-order and Freundlich model. At pH of 10, C0 of 1000 mg/L and t of 10 h, the largest adsorbed amount of EMG@NMDG was 85.79 mg/g. Regeneration experiments were carried out by eluting the adsorbent using HCl. The analysis showed that the adsorption in actual brine was 62.65 mg/g. Therefore, the developed EMG@NMDG aerogel has potential value for the boron extraction from brine and wastewater.

Modeling and application of continuous ion exchanges process for lithium recovery from salt lake brine

A composite model has been developed to simulate and optimize the continuous multi-column lithium adsorption based on the continuous adsorption of lithium from high Mg/Li ratio brines. The model not only simulates all the adsorption columns of the adsorption process, but also the auxiliary equipment connected to the adsorption columns such as pumps and valves, to describe the multi-column continuous lithium extraction process in detail. To improve the efficiency of lithium extraction, a 4-zone, 20-column carousel-type continuous lithium extraction process was proposed and optimized using the composite model. When the feed flow rate was set to 25 mL/min in the adsorption zone, 8 mL/min in the washing zone and 15 mL/min in the product zone, the Li+ extraction rate in the adsorption zone was 98.26%, the lithium loss in the washing zone was 16.12%, the magnesium removal rate in the washing process was 98.77%, the concentration of lithium solution obtained in the product zone was 488.55 mg/L, and the magnesium-lithium ratio was 6.45, with a lithium recovery of 79.68% for the whole continuous lithium extraction process. Overall, the continuous carousel lithium extraction process achieved the expected magnesium separation and continuous lithium extraction from the brine of the Qarhan Salt Lake.

Lithium enrichment and migration mechanism in the evaporation process of sodium aulphate subtype salt lake brine

Based on the natural evaporation experiment conducted on approximately 460 tons of sodium sulfate subtype salt lake brine over a period of more than three years, and utilizing the unique natural energy of Tibet, a new lithium enrichment salt field process called “ three times salt water-twice winter brine “ has been proposed for the Laguocuo brine. On-site natural evaporation achieved high yield of lithium and a “ultra high multiple enrichment” of 134 times. Using first-principles calculations, the adsorption behavior and mechanism of Li+ on the surfaces of Na2SO4·10H2O, NaCl, and KCl crystals were investigated. It was found that the migration of lithium during mineral precipitation in brine evaporation was restricted by the adsorption capacity of Li+ on the surface of minerals (Na2SO4·10H2O > NaCl > KCl). The specific surface area, adsorption concentration of Li+, and surface roughness of the three crystals were tested. The results indicated that the specific surface area and roughness of the three crystals were in the following order: Na2SO4·10H2O > NaCl > KCl, which is consistent with the simulation results. These research findings provide a reference basis for the efficient lithium extraction from Tibetan sodium sulfate subtype salt lakes.

Reconstruction of MgAl-layered double hydroxides to LiAl-layered double hydroxides for scalable lithium extraction from salt lake brine

MgAl-layered double hydroxides (MgAl-LDHs) attract interest for lithium extraction due to their wide availability, high stability, and environmental friendliness. LiAl-layered double hydroxides (LiAl-LDHs) can be obtained by lithiation of MgAl-LDHs, yielding the facile preparation of adsorbents with high selectivity. Herein we synthesized porous MgAl-LDHs by a sol-gel method. MgAl-LDHs can be converted into LiAl-LDHs via dissolution and recrystallization process in LiOH solution. The structure of MgAl-LDHs dissolves, and Mg2+ exchange with Li+ in the solution to generate LiAl-LDHs. Mg2+ enter the solution. MgAl-LDHs and LiAl-LDHs were characterized using X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), N2 adsorption-desorption isotherms and X-ray photoelectron spectroscopy (XPS). The granulation of MgAl-LDHs and LiAl-LDHs was facilitated by chemical/physical cross-linking of sodium alginate using CaCl2 solutions. The performance of lithium extraction was investigated using synthetic brines, and real salt lake brines. The results showed that MgAl-LDHs and LiAl-LDHs adsorbents registered an adsorption capacity of 9.7 and 6.4 mg/g, respectively, at pH = 6 in 300 mg/L of Li+ solutions. The kinetic analysis revealed that granulated MgAl-LDHs and LiAl-LDHs exhibited pseudo-second-order adsorption behavior attributed to the redox behavior. In the brine of East Taigener Salt Lake, the granulated MgAl-LDHs and LiAl-LDHs achieved an adsorption capacity of 15.5 and 9.1 mg/g, respectively. The granulated LiAl-LDHs and MgAl-LDHs are promising for scalable lithium extraction from salt-lake brines.

Anion regulation strategy of lithium-aluminum layered double hydroxides for strengthening resistance to deactivation in lithium recovery from brines

Lithium aluminum layered double hydroxides (LiAl-LDHs) have emerged as the most promising adsorbent for lithium extraction from salt lake brines. However, the development of LiAl-LDHs is impeded by their susceptibility to structural collapse and deactivation during desorption process. Herein, an interlayer anion regulation strategy was proposed to endow LiAl-LDHs with superior resistance to deactivation induced by excessive Li+ deintercalation through strengthening the interlayer interactions. Consequently, a novel LiAl-LDH with interlayer Cl− partially replaced by PO43− (LiAl-LDH-P) was synthesized by coupling PO43− intercalation with Li+ insertion during co-precipitation. Combining DFT calculations and elution strength experiments, it was revealed that the intercalated PO43− could anchor Li+ into the vacancies of Al-O octahedron via high interlayer binding energy and strong electrostatic interaction, which imparted LiAl-LDH-P with an excellent anti-elution deactivation ability. Moreover, LiAl-LDH-P presented distinctly advanced compared to commercialized and reported LiAl-LDHs, with extraordinary Li+ adsorption capacity (9.35 mg/g), selectivity (separation factors of 270.3, 450.3, 453.7 for Li+/Na+, Li+/K+, Li+/Mg2+, respectively), and reusability in Lop Nor brine, even at the ultra-high eluent consumption. Furthermore, the physicochemical properties and Li+-extraction mechanism of the LiAl-LDH-P were investigated as well. This work provides a promising strategy to solve the current deactivation of LiAl-LDHs and offers a prospective adsorbent for Li+ extraction from brine.

Separation performance and fouling analyses of nanofiltration membrane for lithium extraction from salt lake brine

In this study, the separation performance of NF membrane for magnesium and lithium in salt lake brine with a high magnesium-to‑lithium mass ratio and membrane fouling properties were investigated. The results showed that the retention rates for magnesium and lithium were higher than 81 % and less than −69 %, respectively. The mass ratio of magnesium and lithium in the permeate reduced 8.5 times and the yield of lithium was 83 % after separation indicating the effective lithium recovery for DK NF membrane. However, the polyamide functional groups of the DK NF membrane showed redshift after fouling, and inorganic ions (Mg and Ca) and carboxyl groups were increased on the membrane surface. Furthermore, functional layer and spongy porous structures of the NF membrane were damaged after pollution decreasing the effective membrane area and pore size. Moreover, the hydrophilicities of the fouled membranes decreased, while their electronegativities increased. Therefore, the NF membrane exhibited a decreased separation performance after long-term recovery of lithium from brine. Nanofiltration fouling showed that trace calcium in salt lake brine with a high magnesium-to‑lithium mass ratio was the crucial factors on membrane fouling, and thus calcium could be reduced in the recovery of lithium from brine via nanofiltration.