Divalent Ions Research Articles

Chelation-Induced Zwitterion-like Antifouling Behavior on Anionic Poly(3,4-ethylenedioxythiophene) Surfaces.

Antifouling properties are crucial for enhancing the longevity and functionality of biomedical implants, drug delivery systems, and biosensors. Zwitterionic polymers are renowned for their exceptional surface hydration and charge neutrality, which effectively resist biomolecular adsorption and protein attachment. We propose an innovative approach to develop zwitterion-like antifouling surfaces by chelating divalent cations with anionic poly(3,4-ethylenedioxythiophene) (PEDOT) films, specifically PEDOT-PO4 and PEDOT-COOH. The chelation behavior of these films was systematically evaluated using Na+, Mg2+, and Ca2+ ions. Divalent ions, particularly Ca2+ and Mg2+, exhibit a strong affinity for the anionic groups, leading to significant antifouling properties. These modified surfaces effectively repelled both negatively charged bovine serum albumin (BSA) and positively charged lysozyme (LYZ) proteins across various pH environments. This study offers valuable insights into the antifouling characteristics of charged surfaces, enhancing our understanding of how ion-mediated surface modifications influence protein adsorption and interactions.

Enhanced biocatalytic laccase production using agricultural waste in solid-state fermentation by Aspergillus oryzae for p-chlorophenol degradation

Agricultural residues are one of the most cost-effective and readily accessible carbon resources for producing commercially significant enzymes. Several enzymes have been used in different industries like pharmaceuticals, foods, textiles, and dyes that can be generated by various species of microbes found in waste from agriculture. The current research investigated laccase production by Aspergillus oryzae utilizing agricultural wastes. Physical and chemical properties, including pH, temperature, sucrose, yeast extract, and copper sulfate levels, were optimized. The utilization of the response surface methodology along with the centralized composite design method, which assesses multiple media parameters and utilizes a two-level experimental approach, aids in determining the variable and its significance in increasing production quality. The centralized composite design enhancement showed that the optimal conditions for highest laccase activity (623.16 U/mL) were pH 7.0, temperature 25 °C, corn cobs as substrate, sucrose (2.0 %), yeast extract (1.0 %), and copper sulfate (0.1 mM) level. The laccase enzyme was optimized using various pH, temperature, metal ions, and inhibitors combinations. The extracted laccase enzyme maximum activity was attained at pH 6.0 and 40 °C. The inclusion of divalent ions can enhance laccase activity, while the use of various inhibitors decreases laccase activity. Under various pH circumstances, the Aspergillus oryzae laccase enzyme can successfully degrade p-chlorophenol. The present study describes statistically validated optimal methodologies for enhancing laccase synthesis, leading to a laccase production technique that is simultaneously highly efficient and economically profitable, with possible use of p-chlorophenol degradation.

Characterization of Escherichia coli chaperonin GroEL as a ribonuclease

Chaperonins are evolutionarily conserved proteins that facilitate polypeptide assemblies. The most extensively studied chaperonin is GroEL, which plays a crucial role in Escherichia coli. In addition to its chaperone activity, the RNA cleavage activity of GroEL has also been proposed. However, direct evidence of GroEL as a ribonuclease (RNase) and its physiological significance has not been fully elucidated. Here, we characterized the role of GroEL in E. coli as an RNase distinct from RNase E/G activity using in vivo reporter assays, in vitro cleavage assays with varying reaction times, divalent ions, and 5′ phosphorylation status. GroEL bound to single-stranded RNA at nanomolar concentrations. Functional analysis of GroEL chaperonin-defective mutants and segments identified specific regions, and the chaperone active status of GroEL is not a necessary factor for RNase activity. Additionally, RNase activity of GroEL was attenuated by co-overexpression with GroES. Finally, we characterized potential transcripts regulated by GroEL and the conserved RNase activity of GroEL in Shigella flexneri. Our findings indicate that GroEL is a novel post-transcriptional regulator in bacteria.

Micellar Nanogels from Alginate-Based Diblock Copolysaccharides.

Alginates are marine polysaccharides known for their ability to selectively bind calcium ions and form hydrogels. They are widely used in biomedical applications but are challenging to produce as nanogels. Here we introduce a self-assembly route to create stable alginate-based nanogels under near-equilibrium conditions. Guluronate (G) blocks, which interact with divalent cations such as Ca2+, Ba2+, and Sr2+, were extracted from alginates and covalently linked through their reducing end to the reducing end of dextran (Dex) chains, forming linear block copolymers that self-assemble into micellar nanogels with a core-corona structure in the presence of these ions. Real-time dynamic light scattering (DLS) and small-angle neutron scattering (SANS) were used to study the self-assembly mechanism of the copolymer during dialysis against divalent ions. For the G12-b-Dex51 copolymer, we achieved spherical micelles with an 8 nm radius and an aggregation number of around 20. Although the type of divalent cation affected micelle stability, it did not influence their size. Micellar nanogels are dynamic structures, capable of ion exchange, and can disassemble with chelating agents like ethylenediamine tetraacetic acid (EDTA).

Quantifying and mitigating motor phenotypes induced by antisense oligonucleotides in the central nervous system

Antisense oligonucleotides (ASOs) are emerging as a promising class of therapeutics for neurological diseases. When injected directly into cerebrospinal fluid, ASOs distribute broadly across brain regions and exert long-lasting therapeutic effects. However, many phosphorothioate (PS)-modified gapmer ASOs show transient motor phenotypes when injected into the cerebrospinal fluid, ranging from reduced motor activity to ataxia or acute seizure-like phenotypes. Using a behavioral scoring assay customized to reflect the timing and nature of these effects, we show that both sugar and phosphate modifications influence acute motor phenotypes. Among sugar analogues, DNA induces the strongest motor phenotypes while 2'-substituted RNA modifications improve the tolerability of PS-ASOs. Reducing the PS content of gapmer ASOs, which contain a stretch of PS-DNA, improves their toxicity profile, but in some cases also reduces efficacy or duration of effect. We show that this acute toxicity is not mediated by major nucleic acid sensing immune pathways. Formulating ASOs with divalent ions before injection and avoiding phosphate-based buffers modestly improved tolerability through mechanisms at least partially distinct from reduced PS content. Overall, our work identifies and quantifies an understudied aspect of oligonucleotide toxicology in the CNS, explores its mechanism, and presents platform-level medicinal chemistry and formulation approaches that improve tolerability of this class of compounds.

Chloride-salt separation type nanofiltration membranes for efficient crude salt refinement

Application of unrefined crude salt not only leads to a serious equipment scaling and a low product quality, but also increases operational risks and poses health hazards. Therefore, it is essential to refine crude salt prior to its use. However, traditional methods of crude salt refinement are energy-intensive and probably produce additional chemical by-products. In this work, membrane technology was used to accomplish the refinement of crude salt due to its unique characteristics, such as environmentally friendly and lower energy consumption. To improve the separation performance, the membranes were fabricated by simply adjusting the aqueous monomer concentration. For single-salt feed, the membrane (M10) prepared with a high ratio of 10 exhibited excellent salt rejection due to the formation of a thicker and denser PA layer. And it owned a superior MgCl2/NaCl selectivity of ∼22.0, demonstrating that the membrane can achieve outstanding selectivity for mono-/divalent ions. The selectivity of Mg2+/Na+ increased to ∼23.5 for bi-salt feed and further improved to 66.2 for multi-salt feed due to the stronger charge shielding effect. Most importantly, the membrane was also successfully applied in the refinement of crude salt. When using crude salt (NaCl 30 g/L, purity 0.90) as feed, the M10 exhibited both excellent retention of bivalent ions and permeation of univalent ions, resulting in the corresponding Mg2+/Na+ selectivity up to ∼251.6 and the tremendous enhancement in the Na + purity of ∼0.997. This work offers a feasible strategy for crude salt refinement, and could expand to some other potential applications such as resource utilization in the salinization industry and zero-liquid discharge of industrial wastewater.

High-entropy processed high quality and low-temperature cofired LiMgPO4-based dielectric ceramics for low-loss packaged millimeter-wave filters

In this work, we successfully integrated the high-entropy concept into LiMgPO4-based ceramics by strategically substituting Mg2+ with various divalent ions. Through a low-temperature solid-phase reaction method, a series of high-entropy LiMg0.9R0.1PO4 (R = Ni, NiCo, NiCoZn, NiCoZnCu, NiCoZnCuMn) ceramics were prepared successfully, and their MW dielectric properties were found to be heavily influenced by the ionic character, lattice energy, bond energy, entropy, ion radius disorder, and electronegativity of chemical bonds. Remarkably, LiMg0.9(Ni0.2Co0.2Zn0.2Cu0.2Mn0.2)0.1PO4 (LM5RP) ceramics exhibited exceptional MW dielectric properties (εr = 7.43, τf = − 27.6 ppm/°C, and Q × f = 83,216 GHz@13 GHz and 105,889 GHz@28 GHz) when sintered at an extraordinarily low temperature of 900 °C for 2 h. To demonstrate the real-world applicability of the LM5RP high-entropy ceramic, we designed and fabricated a state-of-the-art millimeter-wave (mmWave) filter, operating at 28 GHz, using low-temperature co-fired ceramic (LTCC) packaging technology. The filter exhibited unparalleled performance, featuring a low insertion loss (0.9 dB) and wide stopband suppression (> 17 dB @ 2.14 f0). These groundbreaking findings underscore the immense potential of high-entropy ceramics in revolutionizing advanced MW applications, particularly in the domain of B5G/6 G mmWave communication systems.

Tripolyphosphate-functionalized cellulose: A green solution for cadmium contamination

This study introduces a highly efficient tripolyphosphate -tethered cellulose sorbent for cadmium (Cd2⁺) removal from aqueous solutions. Characterization through FTIR and SEM revealed the material's structural properties. The sorbent achieved 99% Cd2⁺ removal even at a minimal dosage of 0.05 g. Optimal sorption occurred within the pH range of 4–6, influenced by the sorbent's weak acidic functional groups. Rapid kinetics, reaching equilibrium within a minute, and a high sorption capacity (up to 18.03 mg/g at 50 °C) were observed. Langmuir isotherm modeling confirmed monolayer sorption, and thermodynamic studies indicated a spontaneous, endothermic process with increased randomness at the solid-liquid interface. Selectivity studies demonstrated strong Cd2⁺ removal performance in the presence of competing ions, with minimal interference from monovalent ions but notable effects from divalent ions. The sorbent exhibited consistent reusability over multiple cycles. XPS analysis conclusively established an ion exchange mechanism between Cd2⁺ and negatively charged P3O105− groups as the primary removal pathway. This research highlights the potential of TPP-tethered cellulose as a promising sorbent for effective Cd2⁺ remediation.

Selective divalent/monovalent ion partitioning in cation exchange membranes

The selective partitioning of divalent and monovalent counterions through cation exchange membranes immersed in 2:1 and 1:1 binary salt solutions remains unclear, especially at the molecular level. We present a theoretical framework that quantifies these membranes’ sorption of divalent and monovalent ions, incorporating condensed and free variants to reconcile deviations from the ideal Donnan picture observed in published experimental data. This framework explores the membranes’ global and local selective ion sorption characteristics by assessing the effects of competitive ion condensations, where these counterions compete to bind to the fixed charge groups. First, we calculate the thermodynamic property—the global partition ratio—of the membranes immersed in these binary salt solutions, quantifying the partitioning between the binary salt solutions and the membranes. Our theoretical results successfully capture the published experimental partitioning data for membranes immersed in equimolar and non-equimolar 2:1 and 1:1 binary salt solutions. Furthermore, the Donnan potential of the membranes reciprocally changes with the total concentration of 2:1 and 1:1 external salt solutions. However, for the non-equimolar systems at a constant low total concentration, varying the binary solution concentration ratio of 2:1 to 1:1 salts maintains a strong electric potential intensity due to high ionic imbalance. Second, we quantify the local partitioning of the sorbed counterions that are condensed on the crosslinked polymeric chains and those that are mobile in the interstitial solution of the membrane, a variable that is difficult to access experimentally. Accordingly, we can fractionate the sorbed ions into condensed and free states, which mutually govern the membrane’s kinetic and thermodynamic (global and local partitioning) properties.

Initiation of Medial Calcification: Revisiting Calcium Ion Binding to Elastin.

Pathological calcification of elastin, a key connective tissue protein in the medial layers of blood vessels, starts with the binding of calcium ions. This Mini-Review focuses on understanding how calcium ions interact with elastin to initiate calcification at a molecular level, and emphasizes water's critical role in mediating this interaction. In the past decade, great strides have been made in understanding and modeling ion-specific hydration and its effects on biomolecule interactions. However, these advances have been largely absent from our understanding of elastin calcification. Historically, charge-neutral backbone carbonyls and negatively charged carboxyl groups have been proposed as elastin's calcium binding sites. Recently, tropoelastin's only four carboxyl groups have been identified as binding sites from classical molecular dynamics (MD). While carboxyl groups have a much higher affinity for binding calcium ions than backbone carbonyls, conflicting evidence persists for both functional group's importance in elastin calcification. This can be attributed to the fact that divalent ions strongly polarize water, leading to a hydration shell that shields electrostatic forces. The hydration shell surrounding both a calcium ion and either of the proposed binding sites must be displaced to enable binding. Providing our own extended X-ray absorption fine structure (EXAFS) data and complementary simulations, we discuss the potential structures of calcium binding in elastin and review prior knowledge regarding the relative importance of the two proposed binding sites.

Mechanisms determining water permeability and ion selectivity of multilayered glycine-functionalized graphene oxide membranes in saline water reverse osmosis processes: A computational investigation

Non-Equilibrium Molecular Dynamics simulations were performed to examine in detail the mechanisms involved in a reverse osmosis process for the removal of monovalent (Na+, Cl−) and divalent (Mg2+) ions from saline water, using multilayered glycine-functionalized graphene oxide (GO) membranes. We varied parameters such as the degree of functionalization of the GO flakes and the structural flexibility of the membranes and examined their performance in a wide range of applied pressure gradients. In all models examined, water permeability was found to be almost 2 orders of magnitude larger compared to that in conventional reverse osmosis (RO) membranes. High structural flexibility of the membranes was found to increase water permeability due to the formation of additional nanochannels that favor faster water transport. Functionalization of the GO flakes by the glycinate groups resulted in a decrease in water permeability due to the formation of a denser hydrogen-bonding network within the membranes. Three main mechanisms were identified regarding ion selectivity. Due to the overall negative charge of the membranes, the strong adsorption of the Mg2+ ions onto the GO flakes resulted in their full rejection. Weaker adsorption of the Na+ ions led only to their partial rejection. At the same time, the electrostatic repulsion of the Cl− ions by the membranes was found to result in almost full removal levels at high pressure gradients. The rejection of the monovalent ions was found to decrease with the structural flexibility of the membranes and increase with the functionalization of the GO flakes, in response to the changes observed in water permeability on these membrane modifications. The pressure-dependent deformability of the structurally flexible membranes combined with charge accumulation close to the membrane's entrance, resulted in a non-monotonic dependence of the monovalent ion rejection on the applied pressure difference.

Effects of Acid Dissociation and Ionic Solutions on the Aggregation of 2-Pyrone-4,6-dicarboxylic Acid.

The conversion of lignin can produce biomass-derived aromatic compounds such as 2-pyrone-4,6-dicarboxylic acid (PDC), which is a potential sustainable precursor of bioplastics. PDC is a pseudoaromatic dicarboxylic acid that can aggregate in aqueous solution. Aggregation depends upon PDC-PDC, PDC-water, and PDC-ion interactions that are representative of interactions in similar charged, aromatic compounds. These interactions both dictate PDC aggregation and the likelihood that PDC aggregates exhibit parallel stacking configurations that may promote PDC crystallization, which can be leveraged to separate PDC from solution. However, the interplay of interactions that drive aggregation and structure formation, and how these depend upon the charge of PDC and ionic species present in solution, remains unclear. In this work, we investigate PDC aggregation in diverse ionic solutions using all-atom molecular dynamics simulations and molecular clustering analysis. We consider ion-induced dipole interactions by using a modified Lennard-Jones nonbonded model for divalent ions in solutions. From molecular clustering analysis, we derive characteristic parameters to quantify aggregate sizes and parallel stacking configurations. We show that acid dissociation facilitates PDC aggregation in ionic solutions via ion-mediated interactions, and different ionic solutions influence both the likelihood of aggregation and the formation of parallel aggregates. In particular, we find that parallel stacking is primarily found in solutions with monovalent ions, whereas divalent ions promote larger, but less structured, aggregates. These results provide molecular-scale insight into the effects of specific ions on the aggregation of like-charged PDC molecules to inform understanding of related separation processes.

Effects of water salinity and temperature on oil-in-water emulsions stabilized by a nonionic surfactant

The goal of this work is to understand the effect of water salinity of three salts- NaCl, CaCl2, and MgCl2- on oil-in-water (O/W) emulsions stabilized by nonionic surfactants such as Tergitol 15-S-7 (T15S7). The study investigates not only the impacts of mixing speed, water salinity, and temperature but also the combined effects of salt and temperature on emulsion stability. All emulsions were created using ExxsolTM D110 and distilled water, with a surfactant concentration of 0.050 % wt. in the water phase. Two oil fractions (10 % and 25 % by volume) were studied, and oil and water separation interfaces were measured using a state-of-the-art apparatus, which can record and scan videos of free liquid separation. According to the experimental findings, at concentrations higher than the surfactant’s Critical Micelle Concentration (CMC), neither of the divalent salts affects the surface tension of the aqueous solution. Divalent ions, on the other hand, were found to decrease the surfactant’s effectiveness at concentrations lower than the CMC. Conversely, monovalent ions had no effect at low concentrations but further reduced the surface tension at large concentrations. All salts, however, had no effect on the volume of the emulsion for more than 4 h at 25 °C, however at 70 °C, 100 % separation happens in a matter of seconds. Decrease in mixing speed from 2500 RPM to 800 RPM caused the emulsion volume to decrease by at least 72 %.

Humic substances and inorganic ions synergistically precipitate at the gas–liquid interface in a simulation experiment of direct-contact heat and mass transfer processes

Direct-contact heat and mass transfer processes are widely employed in saline wastewater treatment. However, these processes are accompanied by serious ultrafine particle emission, a phenomenon associated with the solute’s transition across the gas–liquid interface. A thorough comprehension of the solute’s behavior at this gas–liquid interface is vital for clarifying the crossing process and guiding particle control strategies. Here, solutions containing saturated inorganic ions and humic substances were evaporated to analyze their behaviors at the gas–liquid interface in an experimental simulation of direct-contact heat and mass transfer processes. It was found that these substances co-precipitated at this interface. Humic substances can bind with inorganic ions via chemical bonds, monovalent ions through cation-π interactions, and divalent ions through electrostatic and chelation interactions. Moreover, humic substances can act as nucleation sites for precipitating inorganic crystals. These distinctive binding mechanisms caused a synergistic relationship between humic substances and inorganic ions during precipitation. Amidst precipitation, humic substances with high humification degrees and large molecular weights were predominantly enriched. Inorganic ions, comprising over 93% of the total precipitate mass, constituted the principal constituents. Among these, Na+, with an enrichment factor of 2.10, precipitated more readily at the gas–liquid interface compared to divalent ions. These conclusions concerning the binding mechanisms of humic substances and inorganic ions, along with their precipitation characteristics, were validated in the submerged combustion evaporation process of membrane-concentrated leachate.

Advanced MOF/MXene heterostructure with carbon aerogel to boosts the ions movement in asymmetric supercapacitors and hydrogen production

Supercapacitors represent a promising avenue for advanced energy storage solutions. However, achieving devices that simultaneously possess all the ideal properties, such as high capacitance, fast charge-discharge rates, and excellent cyclability, remains a significant challenge. Herein, a facile approach for fabricating carbon aerogel-induced chromium metal-organic framework (CA@MIL-101) integrated with titanium carbide MXene (CA@MIL-101-(Cr)/Ti3C2Tx) nanocomposites was demonstrated via hydrothermal method. The CA@MIL-101-(Cr)/Ti3C2Tx nanocomposites offer numerous divalent ion active sites and significantly improve charge transfer kinetics, attributed to their interconnected porous structure. This novel anode exhibits an outstanding specific capacity of 1632 Cg-1 with a PVDF binder-based electrode and a high rate of performance. Moreover, a full-cell supercapacitor was developed with carbon aerogel as the cathode and CA@MIL-101 (Cr)/Ti3C2Tx as the anode. With its hierarchical pore structure and functional groups, the CA@MIL-101 (Cr)/Ti3C2Tx anode achieves an energy density of 38 Wh-kg−1, a high-power density of 1280 W-kg−1, and robust anti-self-discharge behavior. The CA@MIL-101 (Cr)/Ti3C2Tx//CA supercapattery uses both adsorption/desorption processes and faradaic reactions for charge storage. The synthesized materials also perform exceptionally well electro-catalytically. This research advances high-performance CA@MIL-101 (Cr)/Ti3C2Tx electrodes, enhances understanding of supercapacitor charge storage, and paves the way for next-generation energy storage technologies.

Polyamide nanofiltration membrane modified with defective covalent organic framework interlayer for selective ion sieving

Generally, thin-film composite (TFC) membranes prepared using piperazine (PIP) and trimesoyl chloride (TMC) exhibit good Na2SO4 rejection, but their MgCl2 rejection is not satisfactory. In this study, a defective covalent organic framework (COF) interlayer with residual unreacted amine groups was fabricated via interfacial polymerization (IP) by changing the catalyst concentration. Introduction of the COF layer into a polyamide (PA) separation membrane modified the pore size of the PA layer, thereby improving the rejection of divalent cations. The pore size of the PA layer decreased and the surface morphology of the membrane was converted from nodular to a hybrid morphology of “ridge-and-valleys’’ and nodules, indicating that the residual unreacted amine groups on the COF interlayer successfully reacted with the acyl chloride groups. The optimal membrane (PIP/COF-A/PES) exhibited high rejection of divalent ions (Na2SO4 of 98.3% and MgCl2 of 94.3%), and the membrane showed excellent capability for separating mono/divalent ions. Overall, a method of preparing nanofiltration membranes by modifying the PA layer to enhance the rejection of divalent cations was demonstrated.

Synthesis of carboxyl group functionalized polyhedral oligomeric silsesquioxane for fabricating ultrastable foams driven by high temperature and salinity

Aqueous foams are thermodynamically unstable systems, and their instability increases with temperature and salinity. In this study, we successfully synthesized an amphiphilic polyhedral oligomeric silsesquioxane, POSS-NH2-BTCA, featuring phenyl and carboxyl groups, through a substitution reaction. Highly stable foams were prepared under temperatures conditions ranging from 50 to 90 °C and salinity levels between 20 and 80 g/L. Rheological tests and scanning electron microscopy analysis show that the interactions between divalent ions and carboxyl groups improve the film strength. However, the half-life of the drainage only increased from 38 s to 55 s. Therefore, the enhancement in foam stability is believed to be caused by the inhibition of coarsening and coalescence rather than the suppression of drainage. The strategy for fabricating amphiphilic nanoparticles can serve as a reference for designing new foam stabilizers for high temperature and salinity conditions.

Impacts of polystyrene nanoplastics on microgel formation from effluent organic matter

Municipal effluents discharged from wastewater treatment plants (WWTPs) are considered major contributors of nanoplastics (NPs) and dissolved effluent organic matter (dEfOM) to environments. Due to their small sizes, NPs can travel easily in waterways and evade wastewater treatment processes, and may directly interact with dEfOM, altering their environmental fates. However, although much research has examined the impact of natural organic matter on NPs, the interactions between NPs and dEfOM remain unexplored. This study investigated the influences of NPs on the behavior and capacity of dEfOM aggregation and surface granularity, and identified the possible aggregation mechanism. We also adjusted the salinity of water samples to simulate scenarios based on WWTP–sea continuums. Our data suggest that dEfOM can self-assemble with 55 nm polystyrene NPs to form microgels, particularly under high salinity conditions. NPs accelerates the formation speed and number of dEfOM aggregates, but the sizes of the aggregates remain largely unchanged. The relative particle counts at a salinity of 34 psu increased by 300 % compared to the control group. The potential mechanism behind NPs-microgels aggregation is likely driven by the synergistic effect of the divalent ion crosslinking and hydrophobic interactions between EfOM and NPs. Notably, NPs incorporation into microgels decreases the surface granularity, thereby possibly affecting settling velocity and colonization of aggregates, as well as microbial attachment and community diversity. Overall, our findings demonstrate the potential influence of NPs on dEfOM assembly and surface properties following effluent discharge, and can inspire further relevant studies on microorganism interactions, removal technologies, and the environmental transport of NPs.

Polyethyleneimine Modified Two-Dimensional GO/MXene Composite Membranes with Enhanced Mg2+/Li+ Separation Performance for Salt Lake Brine.

As global demand for renewable energy and electric vehicles increases, the need for lithium has surged significantly. Extracting lithium from salt lake brine has become a cutting-edge technology in lithium resource production. In this study, two-dimensional (2D) GO/MXene composite membranes were fabricated using pressure-assisted filtration with a polyethyleneimine (PEI) coating, resulting in positively charged PEI-GO/MXene membranes. These innovative membranes, taking advantage of the synergistic effects of interlayer channel sieving and the Donnan effect, demonstrated excellent performance in Mg2+/Li+ separation with a mass ratio of 20 (Mg2+ rejection = 85.3%, Li+ rejection = 16.7%, SLi,Mg = 5.7) in simulated saline lake brine. Testing on actual salt lake brine in Tibet, China, confirmed the composite membrane's potential for effective Mg2+/Li+ separation. In the actual brine test with high concentration, Mg2+/Li+ after membrane separation is 2.2, which indicates that the membrane can significantly reduce the concentration of Mg2+ in the brine. Additionally, the PEI-GO/MXene composite membrane demonstrated strong anti-swelling properties and effective divalent ion rejection. This research presents an innovative approach to advance the development of 2D membranes for the selective removal of Mg2+ and Li+ from salt lake brine.

Brine separation with polyamide and polyimine thin film composite nanofiltration membranes obtained from biobased monomers

Thin film composite (TFC) membranes are state-of-the-art membranes that are widely applied in water treatment and seawater desalination. However, these membranes are typically prepared using petrochemical-based monomers and toxic solvents. Herein, plant-based monomers, namely priamine (PA), 2,5-furandicarboxaldehyde (FDA) are used to fabricate green PA–FDA TFC membranes via interfacial polymerization. Additionally, PA was also combined with trimesoyl chloride (TMC) to obtain PA–TMC TFC membranes. The reaction conditions were varied to investigate their effects on membrane morphology and performance. The resultant membranes exhibited smooth surfaces with an average roughness ranging from 15 to 30 nm, and increasing the monomer concentration increased the film thickness. The PA–TMC free-standing films had higher thicknesses (130–300 nm) than the PA–FDA films (36–122 nm). Furthermore, PA–TMC and PA–FDA films were hydrophobic due to the long aliphatic chains of PA. Moreover, PA–TMC membranes demonstrated a water permeance of ∼4 L m−2 h−1 bar−1 with 74% NaCl rejection, while PA–FDA membranes achieved better NaCl rejection (∼80%) but lower water permeance (0.3–4 L m−2 h−1 bar−1). Applied in brine separation, the membranes demonstrated ∼90% divalent ion rejection and only 70% monovalent ion rejection. The proposed plant-based monomer combination provides a steppingstone toward green TFC membrane manufacturing for water treatment and desalination applications.