Oilfield brine, a by-product of oil and gas extraction, contains valuable resources such as Li+, K+ and Ca2+, offering potential utilisation benefits but also presenting separation challenges. We developed a reaction-coupled separation strategy to separate Ca2+ and Li+ while simultaneously synthesising a calcium-based layered double hydroxide (Ca-based LDH) from the brine. This technology enables the recovery of over 90 % of Ca2+ into the solid product, with 98.5 % of Li+ retained in the liquid phase, achieving highly efficient separation of Ca2+ and Li+. The resulting Ca-based LDH demonstrated excellent capacity for removing heavy metals, such as Cu2+, Ni2+ and Zn2+, from electroplating wastewater. The removal capacities reached up to 384.2 mg/g for Cu2+, 319.3 mg/ g for Ni2+ and 367.9 mg/g for Zn2+. In both single-cation and mixed-cation wastewaters, metal concentrations were dramatically reduced to parts-per-billion (ppb) levels. Kinetic studies indicated rapid adsorption behaviour of Cu2+, Ni2+ and Zn2+ by the Ca-based LDH. Mechanistic analysis revealed that Ca2+ ions in the LDH layers are isomorphously substituted by Cu2+, Ni2+ and Zn2+ from the solution, forming Cu-, Ni-and Zn-containing LDHs with enhanced structural stability. Additionally, the released Ca2+ ions precipitate with CO32-, derived either from intercalated anions or carbonate in the water. Such conditions promote further substitution of Ca2+ in the LDH layers by Cu2+, Ni2+ and Zn2+, resulting in robust metal removal and ultralow residue concentrations in the treated wastewater. This work presents an efficient, economical and sustainable approach for the simultaneous separation and utilisation of oilfield brine resources and treatment of electroplating wastewater.

Cobalt-free manganese-based layered oxides such as LiNi0.5Mn0.5O2 are promising cathodes for next-generation high-energy-density lithium-ion batteries owing to their high theoretical capacity. However, their structural instability in highly delithiated states leads to considerable degradation of both the surface and bulk phases during cycling, limiting their applicability. To address this structural instability, a "pinning" and "pillaring" strategy via titanium doping is proposed herein. Titanium ions act as "pillars" in highly delithiated states in the bulk structure, enhancing phase transition reversibility during cycling. In situ and ex situ X-ray diffraction analyses confirm that Titanium doping stabilizes the bulk structure within 3.0-4.8 V at room temperature. X-ray photoelectron spectroscopy reveals that Titanium ions form a "cationic barrier" at the surface, anchoring lattice oxygen and suppressing undesired phase transformations. This dual mechanism endows the 3 % Titanium-doped material with excellent cycling stability. It exhibits an initial discharge capacity of 157.7 mA h g-1 at C/2 and retains 83.45 % of this capacity after 120 cycles. This represents a 24.17 % increase in initial capacity and a 41.30 % improvement in capacity retention compared to those of undoped LiNi0.5Mn0.5O2. The voltage decay rate of the doped material also reduces to 1.64 mV per cycle, indicating a 90.24 % improvement. The proposed approach is a viable strategy for advancing Cobalt-free manganese-based layered oxides for use in high-energy-density lithium-ion batteries.

The growing demand for lithium resources necessitates efficient and sustainable extraction from salt-lake brine, a process significantly challenged by their low Li+ concentration and high Mg/Li ratios. Adsorptive extraction using aluminum-based layered double hydroxides (LDHs) is promising but limited by modest capacity and structural instability during delithiation. To address this, a series of cation-doped Al-based LDHs were synthesized via a co-precipitation strategy. Comprehensive characterization demonstrated that Zn2+ doping was most effective for elevating lithium adsorption capacity. It induced lattice expansion, increasing the (003) interplanar spacing from 0.744 nm to 0.767 nm, and significantly enhanced textural properties, and improved hydrophilicity (contact angle of 6.7 degrees). Consequently, the optimal adsorbent, LDH-Zn, exhibited remarkable performance in Qarhan Salt Lake old brine. It achieved exceptionally high Li+/Na+ and Li+/Mg2+ selectivity of 1253 and 365, respectively. The Li+ adsorption capacity reaches 10.03 mg/g, which is 31% higher than that of pristine LDH, with kinetics following a pseudo-second-order model. Remarkably, Zn2+ doping drastically improved thermal and cyclic stability: the material retained 97% of its capacity after elongated delithiation of 6 h at a high temperature of 80 degrees C, and the granulated form exhibited less than 5% capacity loss over 20 adsorption-desorption cycles. 27Al NMR spectroscopy confirmed the stabilization of the Al3+ coordination environment. It is ascribed to the robustness of layered structure, weakening phase transformation. This work establishes cation doping as a potent strategy for developing high-performance, durable Al-based adsorbents for practical lithium recovery from high Mg/Li ratio brine.

The development of third-generation concentrating solar power (CSP) systems demands molten salts with excellent thermal stability and high heat-storage capacity. In this study, molten salt nanocomposites suitable for thermal storage in third-generation CSP systems were prepared by incorporating 0.3-1.2 wt% nano-Al2O3 and SiO2 into the ternary sulfate 52 mol% Na2SO4-7 mol% K2SO4-41 mol% MgSO4 (NKM). The resulting nano-composites were characterized through thermophysical measurements and molecular dynamics (MD) simulations. The specific heat capacity exhibited a non-linear dependence on nanoparticle concentration, with an optimum at 0.6 wt%. At this loading, the cp increased to 1.52 J g-1 degrees C-1 with Al2O3 (+15%) and 1.69 J g-1 degrees C-1 with SiO2 (+28%). Nanoparticles caused a modest rise in viscosity while having minimal effect on density. XRD, SEM, and EDS analyses revealed phase evolution during heating, including the formation of K2Mg2(SO4)3 and the transformation of Na6Mg(SO4)4. At higher nanoparticle loadings (>= 0.9 wt%), particle agglomeration accounted for the decline in cp. MD simulations were further used to explore the mechanism underlying the enhancement in specific heat capacity: nanoparticles shorten cation-anion distances and promote the formation of a semi-solid interfacial layer whose thickness increases with temperature. These structural features are consistent with the experimentally observed increase in cp, suggesting that they may contribute to the improved heat storage performance. This work demonstrates a viable strategy for developing high specific heat molten salt nanocomposites for third-generation CSP systems.

Lithium is essential for electric vehicles and renewable energy storage, yet its sustainable recovery from salt lake brines remain challenging. Forward osmosis (FO) offers a low energy alternative, but the lack of mechanistic understanding of draw solute effects limits process optimization. Here, we establish a multi-scale framework integrating experiments, COMSOL, and Molecular Dynamics (MD) simulation to elucidate how draw solute properties govern lithium concentration in FO process. Experimental screening identifies MgCl₂ as the optimal draw solute, achieving the highest water flux (8.68 L·m−2·h−1), while MgSO₄ exhibits the lowest flux but minimal reverse salt flux (0.81 g·m−2·h−1). COMSOL reveals that high Cl− diffusivity mitigates concentration polarization, whereas SO₄2− causes severe solute accumulation at the membrane surface. MD simulation confirms stronger interfacial accumulation of SO₄2− and greater water permeation in the MgCl₂ system. Using 1.0 mol/L MgCl₂, lithium concentration factor of 3.63 is achieved. This work provides a predictive, mechanism driven framework for draw solute selection, linking molecular level interactions (hydration radius, diffusivity, steric hindrance) to module scale polarization behavior and process performance, providing theoretical support for the membrane extraction of lithium resources.

Nanofiltration membranes possess favorable application merits in the separation of metal ions and the recycling of acid solutions in acidic wastewater and it is inevitable that these membranes will experience degradation when exposed to acidic environments. Herein, a hierarchical strategy encompassing macroscopic performance decline, nano-structural evolution and molecular-level chemical bond disruption was adopted to explore the performance degradation and deterioration mechanisms. Firstly, the flux, permeance and rejection rates of polyamide NF membranes with varying aromatic types (fully aromatic NF90 membrane versus semi-aromatic DK membrane and NF270 membrane) and pore sizes (NF90 membrane and DK membrane with small pore sizes versus NF270 membrane with larger pore sizes) were experimentally evaluated and analyzed after degradation in different acidic solutions. Secondly, the surface morphology, chemical composition, hydrophilicity, and surface charge of the membranes before and after degradation were investigated using corresponding characterization methods. It was found that acidic conditions significantly affect both the surface properties and structure of the membranes, thereby influencing their separation performance. Meanwhile, nitric acid and sulfuric acid induced varying degrees of chemical attack on the chemical composition and surface properties of the membrane, resulting in distinct deterioration patterns. Moreover, molecular dynamics simulations and density functional theory calculations were employed to reveal the variations in permeation behavior of membranes and the evolution in amide bonds. The correlation mechanisms between the degradation process and the structural properties of the membranes were elucidated from through water molecule transport and chemical molecular bond analyses. This study prompts the research of deterioration mechanism of polyamide NF membranes in acidic environments and advances the upgrading of acid wastewater treatment to "precise separation, resource recovery and acid reuse" via NF membrane technology.

Molten nitrate salts are among the most promising heat transfer and storage media for concentrating solar power applications. In this study, a series of Mg(NO 3 ) 3 -NaNO 3 -KNO 3 (MNK) ternary molten salts were fabricated via a one-step synthesis strategy involving the dehydration of Mg(NO 3 ) 2 ·6H 2 O. The thermal decomposition behavior, phase transition characteristics, and cycling durability of the as-prepared samples were systematically investigated by thermogravimetry-differential scanning calorimetry (TG-DSC) coupled with X-ray diffraction (XRD). Compared with the original hydrated MNK salt, the anhydrous MNK composite exhibited a significant enhancement in thermal stability. The onset decomposition temperature was elevated from 404.1 to 457.6°C, extending the upper operational limit to 450°C. Concurrently, the endothermic melting peak shifted from 157.5 to 148.2°C, accompanied by an increase in the latent heat of fusion from 66.61 to 88.71 J·g -1 . TG analysis revealed a reduction in the mass loss rate during long-term thermal exposure, indicating suppressed deterioration. Furthermore, XRD patterns confirmed the structural integrity of the anhydrous MNK salt after thermal cycling, demonstrating improved phase stability. Owing to its favorable thermophysical properties and scalable preparation, this anhydrous MNK ternary molten salt represents a viable candidate for high-temperature thermal energy storage.

Current concentrating solar power (CSP) systems operate below 550°C, achieving annual electricity generation efficiencies of 10%–20%, which primarily employs nitrate molten salts as heat transfer fluids (HTFs). However, nitrate salts decompose at temperature exceeding 600°C, rendering them unsuitable for next-generation CSP systems, which aim to operate above 700°C. This review presents the first comprehensive analysis of high-temperature molten salts for third-generation CSP systems. This highlights the potential of carbonates, chlorides, and sulfates as HTFs due to their extended operational temperature ranges. Guided by phase diagrams, multicomponent molten salts are systematically engineered to achieve desirable thermal properties. The review provides a detailed synthesis of compositions and working temperature ranges for these molten salts, with a particular focus on underexplored sulfate-based salts. It consolidates critical data on the melting points and phase compositions of multicomponent sulfates and examines advancements in thermal property enhancements, including the integration of nanoparticles. By summarizing the latest progress and identifying future research directions, this work offers invaluable insights into the design and application of high-temperature molten salts in next-generation CSP systems.

Selective electrodialysis is a promising method for extracting lithium from salt lake brines with a high Mg/Li mass ratio. However, membrane fouling is a significant challenge affecting its separation performance and stability. This study investigated the fouling mechanisms of monovalent cation exchange membranes (MCEMs) during the Mg-Li separation process in brines. Over prolonged operation, membrane fouling and structural degradation lead to a significant decline in Mg-Li separation performance, while increasing energy consumption. Due to the high salinity (246.50 g/L), high Mg/Li mass ratio, and organic-containing (258.60 g/L) of brines, dense inorganic and organic fouling layers form on the membrane surface through concentration polarization, increasing the hydrophobicity and roughness of the membrane surface and weakening the positive charge of the functional layer. Notably, the catalytic hydrolysis mechanism facilitated by magnesium hydroxide and the quaternary ammonium group on the functional side of MCEMs result in more severe fouling. In addition to changes in the surface morphology of the membrane, Time-of-Flight Secondary Ion Mass Spectrometry (TOFSIMS) reveals that the long-term accumulation of high-salinity ions and foulants can disrupt the cross-linking structure between membrane layers. This disruption not only causes cracks and damage to the functional layer but also exposes the underlying support layer, further exacerbating structural failure and performance degradation of the membrane. Molecular dynamics simulations further demonstrate an increased distance between the functional and substrate layers, reduced electrostatic attraction, thus decreasing the electrostatic repulsion for Mg2+. The coupling of membrane fouling and membrane structure degradation significantly increases the resistance to migration of Li+ while reducing the resistance to Mg2+, resulting in decreased Mg-Li separation performance. These findings provide insights for developing strategies to control membrane fouling.

This study investigates Ca(NO3)2 solutions across varying concentrations, revealing that Ca2+ maintains a coordination number of similar to 8 whereas NO3(-) hydration decreases with concentration. At high concentrations, NO3(-) partially replaces water molecules in the first coordination shell of Ca2+, forming ion pairs and clusters via bidentate and monodentate coordination modes. Ion aggregation disrupts and restructures the hydrogen-bond network. These findings offer essential insights into ion-solvent interactions in concentrated electrolytes.

The corrosion behavior of 316 L stainless steel (316 L) and 347 stainless steel (347) at 500 degrees C in a novel molten salt (KNO3-NaNO2-KNO2, KNK) is investigated. The corrosion behavior is determined by recording the weight changes of the stainless steels at different time intervals and analyzing the KNK compositional changes before and after corrosion, combined with changes in the morphology and intrinsic characteristics of the stainless steels. X-ray diffraction (XRD) and inductively coupled plasma mass spectrometry are employed to characterize the phase and component of KNK; XRD, scanning electron microscopy/energy-dispersive X-ray spectroscopy are used to characterize the composition, morphology and microstructure of the corrosion products on the surface. Analyses of the changes in KNK composition before and after corrosion, as well as the surface morphology and composition of the stainless-steel sheets, show that the corrosion product of 347 is more prone to Fe3O4, whereas the corrosion product of 316 L is more prone to Fe2O3. Fe3O4 formation devitalizes the corrosion reactions to some extent; consequently, 347 exhibits stronger corrosion resistance than 316 L.

The global shift towards low-carbon energy storage has increased interest in sodium-ion batteries (SIBs) as a safer, cost-effective alternative to lithium-ion batteries. However, the commercial viability has been limited by compatibility issues between high-energy-density cathode materials, such as Na3V2(PO4)2F3 (NVPF), and high-voltage electrolytes. Addressing the challenges, H-NaODFB (comprising 93.91% NaODFB and 5.85% NaBF4) electrolyte significantly improves the electrochemical performance and stability of NVPF cathodes. Na/NVPF half-cells using H-NaODFB electrolyte retained 92.4% capacity after 900 cycles, while Na/Na symmetric cells demonstrated a cycle life exceeding 600 h at 0.5 mA cm-2. The superior performance is attributed to improved Na+ (de)intercalation reversibility, lower interfacial impedance (619.8 vs. 10,650.0 Ω), and faster reaction kinetics compared to NaODFB alone. Advanced time of flight-secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS) and aberration corrected transmission electron microscope (AC-TEM), combined with first-principles calculations, revealed that NaBF4 in the H-NaODFB electrolyte plays a critical role in forming a stable cathode electrolyte interphase (CEI). The CEI consists of an initial inorganic and organic layer, followed by a fluoroborate layer, and finally a stable organic-inorganic polymeric layer, enhancing electrode stability and preventing over-oxidation. These findings provide valuable insights for designing high-performance electrolytes for SIBs.

Salt-lake brines have emerged as a promising source of lithium; however, the separation of Li+ ions from other coexisting ions remains challenging. To surmount this issue, a three-dimensional wrinkled membrane that was based on a H1.6Mn1.6O4 (HMO) ion sieve and comprised graphene oxide (GO) and hydroxylated graphene (GOH) was fabricated in this study. The designed structure provided abundant channels for ion migration. The hydroxyl groups of graphene allowed the membrane to exhibit improved Na+-Li+ sieving ability. The lithium adsorption capacity of HMO-GOH/GO (20.6 mg/g) was considerably higher than that of HMO (8.9 mg/g) in a low- concentration lithium solution. The adsorption capacity and separation coefficient of HMO-GOH/GO in a high-sodium brine of Na/Li = 49:1 (48.0 mg/g and 47.1) were higher than those of HMO (21.6 mg/g and 29.3, respectively). The adsorption capacity of HMO-GOH/GO remained at 90.8 % of its initial value after 10 adsorption-desorption cycles, thus demonstrating excellent cyclic stability. HMO/GO-GOH shows higher specific capacitance than HMO based on the cyclic voltammetry results. The density functional theory calculations on adsorption energy of Li+center dot 4H2O and the energy barrier across the GOH pore confirm the Na+/Li+ sieving capability. The adsorption mechanism was studied by in situ Raman spectroscopy, verifying the formation of Li-O bond during lithium adsorption. Overall, this study provides guidance in the pursuit of a remedy for Na-Li separation.

Membrane fouling, particularly Ca2+-induced scaling on cation exchange membranes (CEM), hinders the application of electrodialysis in lithium extraction. This study investigated the fouling mechanisms of Ca2+ coexisting with Cl- and SO42- on sulfonated CEM, using CaCl2 and CaSO4 solution as the targeted foulants. The conductivity, pH, turbidity, particle size distribution, chemical composition and morphology of the membrane surface were monitored to verify the evolution of the bulk solution and the membrane during the Ca2+-induced fouling. Online detection of conductivity and pH revealed distinct trends in fouling solutions containing Ca2+-Cl- and Ca2+-SO42-. Noticeable changes in turbidity and particle distribution were observed in the concentrated chamber of the highly saturated Ca2+-SO42- solution, whereas the concentrated chamber of the Ca2+-Cl- solution showed turbidity and particle size distribution similar to the initial values. SEM showed that there are different morphologies of scaling crystals in the two types of solution. These fundamental differences are the root cause of the distinct fouling mechanisms between the Ca2+-Cl- solution and Ca2+-SO42- solution. To further investigate the fouling mechanisms, the electrochemical impedance spectroscopy (EIS) was employed to differentiate the impedance of the electric double layer and diffusion layer, providing insights into the characteristics of the CEM-solution interfaces fouled by different lithium-containing solutions. Additionally, adsorption experiments, quartz crystal microbalance with dissipation (QCM-D) and computational simulations (COMSOL, DFT) were conducted to provide detailed insights into the effects of fouling solutions on the properties of the desalted solution, the probability of crystal precipitation, and particularly the interaction between Ca2+ and the functional sites on the CEM. Finally, the Ca2+-induced scaling mechanism of CEM for enriching the lithium-containing solutions with and without SO42– was proposed, elucidating the synergistic effects of Ca2+-induced crystallization in the bulk solution and Ca2+ adsorption on the CEM surface. The research results could offer theoretical guidance for developing pollution control strategies.

With the rapid development of electric vehicles and smart grids, the demands for energy supply systems such as secondary batteries are increasing exponentially. Despite the world-renowned achievements in portable devices, lithium-ion batteries (LIBs) have struggled to meet the demands due to the constraints of total lithium resources. As the most promising alternative to LIBs, sodium-ion batteries (SIBs) are generating widespread research enthusiasm around the world. Among all components, the cathode material remains the primary obstacle to the practical application of SIBs due to its inability to match the performance of other components. Na3V2(PO4)3 (NVP) stands out as a promising cathode material for SIBs, given its suitable theoretical specific capacity, appropriate operating voltage, robust structural stability, and excellent ionic conductivity. In this article, we first review recent modification strategies for NVP, including conductive substance coating, ion doping (single-, dual- and multi-site doping) and morphology modulation (from zero-dimensional (0D) to three-dimensional (3D)). Subsequently, we summarize five ways in which density functional theory (DFT) calculations can be applied in guiding NVP modification studies. Furthermore, a series of emerging studies combining DFT calculations are introduced. Finally, the remaining challenges and the prospects for optimization of NVP in SIBs are presented.

High thermal stability molten salt is vital for the third-generation concentrating solar power plants. This study investigates the potential of sulfates in the third-generation CSP, 52%Na2SO4-48%MgSO4 (NM) binary molten salt and 52%Na2SO4-7%K2SO4-41%MgSO4 (NKM-12) ternary molten salts were designed and prepared for thermal energy storage. The addition of 7%K2SO4 to NM significantly enhances its thermal properties, with thermal stability increasing from 964.61 degrees C to 1045.79 degrees C and specific heat capacity rising from 1.17 J center dot g-1 center dot degrees C-1 to 1.32 J center dot g-1 center dot degrees C-1 in the liquid state, while also reducing viscosity. In-situ X-ray diffraction (In-situ XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) were employed to analyze the structural transformations in NM and NKM-12 during heating, revealing the phase transition of Na6Mg(SO4)4 and the formation of K2Mg2(SO4)3 in NKM-12. Since it is difficult to experimentally characterize the property changes of molten salts under ultra-high temperatures, molecular dynamics simulations were used. The simulations indicate that K+ are farther from SO42- compared to Na+ and Mg2+, and K+ have the most coordination number with SO42-. The distance between K+ and SO42- changes significantly with temperature, increasing by 3.5 % as the temperature rises from 680 degrees C to 850 degrees C. This increase weakens the interaction between them, which explains the reduction in density and viscosity after the addition of K2SO4. From an energetic perspective, the lower energy barrier between K and S supports the increased ion separation, further enhancing the molten salt's performance. These findings provide valuable insights into the design of next-generation high-temperature thermal energy storage materials, contributing to the development of more efficient CSP systems.

This study systematically investigated the dissolution equilibrium of lithium carbonate (Li2CO3) in mixed Na2CO3-NaCl aqueous solutions through isothermal dissolution experiments spanning 283.15–353.15 K. Precise solubility determinations were conducted using a gravimetric analysis under controlled thermodynamic conditions. The obtained solubility data were successfully correlated with the Extended Debye–Hückel (E-DH) model, yielding residual standard deviations below 0.09, which validates the model’s applicability in this ternary system. Both experimental observations and theoretical predictions confirmed that increasing the salt molality enhances the synergistic suppression of the Li2CO3 solubility through combined common-ion and salt effects. The thermodynamic analysis revealed the dissolution process to be exothermic (ΔHd < 0), and entropy change dominates (ξS ≈ 78%), with negative entropy changes (ΔSd < 0) indicating predominant hydration ordering effects. These mechanistic insights establish critical thermodynamic benchmarks for optimizing lithium carbonate precipitation processes in brine lithium extraction operations.

The tail liquid generated from lithium carbonate production in salt lake brine is termed lithium-bearing mother liquor. This mother liquor exhibits a complex composition, with the Li+ concentration typically around 1.5 g L-1, representing a significant lithium resource. Preparing lithium phosphate (Li3PO4) from this mother liquor is critical for efficient lithium recovery. However, the lack of data on the thermodynamic behavior and Li3PO4 crystallization in such complex solutions has hindered the high-efficiency recovery of lithium resources. In this study, the solubility of Li3O4 in sodium carbonate solutions was determined using the dynamic dissolution equilibrium method. The effects of temperature and sodium carbonate concentration on solubility were analyzed, and experimental data were correlated using an exponential equation. Results indicated that the solubility of Li3PO4 in pure water and sodium carbonate solutions increases with temperature and sodium carbonate concentration. The supersolubility of Li3PO4 in LiCl-Na2CO3 electrolyte solutions was measured via turbidimetric analysis, and the metastable zone width (MSZW) was determined. The supersolubility of Li3PO4 significantly decreased with rising temperature. In contrast, supersolubility initially increased and then decreased with higher Na2CO3 concentrations, with reactant concentration being the decisive factor driving the crystallization reaction. Furthermore, the MSZW narrowed at elevated temperatures. Thermodynamic functions (ΔS d, ΔH d, and ΔG d) for the dissolution process were calculated via the van't Hoff equation, confirming that Li3PO4 dissolution is a spontaneous and endothermic process. Based on solubility and supersolubility data, a novel process was developed to prepare battery-grade Li3PO4 (purity: 99.80%) from salt lake mother liquor. The results of Raman, FTIR, TG and SEM suggested that the prepared lithium phosphate was pure phase. This study provides fundamental physicochemical data and theoretical insights for the efficient separation and extraction of lithium resources from lithium precipitation mother liquor.