Search Results (370)

Increasing water scarcity in arid regions has prompted the mining industry to develop strategies to maximize water recovery and reuse, especially in tailings treatment processes. In this context, the present investigation evaluated the effects of sodium polyacrylate (NaPA) on the compressibility and viscoelasticity of clayey tailings in the presence of hard water containing calcium and magnesium. To this end, clayey slurries were analyzed using rheological tests (rheograms and oscillatory viscoelasticity), zeta potential measurements, and compressibility tests using batch centrifugation. The yield stress was determined using the Herschel–Bulkley model, while the compressive yield stress (Py(Φ)) was calculated as a key indicator to characterize the degree of sediment consolidation. The results showed that NaPA, due to its anionic nature and high degree of ionization at pH 8, induces effective particle dispersion by increasing electrostatic repulsion and decreasing the interaction force between particles, which reduces both rheological parameters and compressive yield stress. For the 70/30 quartz/kaolin mixture, the yield stress decreased from 70.54 to 61.64 Pa in CaCl₂ and from 57.51 to 52.95 Pa in MgCl₂ in the presence of NaPA. It was also observed that suspensions in the presence of magnesium ions presented greater compressibility than those with calcium, attributable to the greater hydration radius of magnesium (10.8 Å), which favors less dense and more easily deformable network structures. Furthermore, a higher proportion of kaolin in the mixture resulted in higher yield stresses, a product of the clay’s laminar structure, colloidal size, and high surface area, both in the absence and presence of NaPA. Overall, the results show that incorporating NaPA significantly improves the compressibility and rheology of clayey tailings in hard water, offering a promising alternative for optimizing water recovery and improving tailings management efficiency in the context of water restrictions. Full article

Wastewater contains dyes originating from textile industries, and above a certain concentration, they can become dangerous due to their high toxicity. Divalent and trivalent metal coagulants, usually aluminum- or iron-based, have been studied worldwide. However, tetravalent coagulants, such as tin chloride, have not yet been extensively studied for application in wastewater treatment. Therefore, in this study, three types of coagulants were examined: SnCl₄, Cs, and a hybrid composite (CS@Sn) in two different mass ratios, abbreviated hereafter as CS@Sn_5% and CS@Sn_50%. The formation of the suggested CS@Sn hybrid coagulants was confirmed by applying SEM, XRD, and FTIR techniques. The results showed that the optimum conditions for RB5 removal was the addition of 20 mg Sn/L SnCl₄ (97.8%) and 50 mg Sn/L of CS@Sn_50% (64.8%) at pH 3.0. In addition, SnCl₄ was found to be an effective coagulant for all the examined anionic dyes, but it was not as effective for cationic dyes. Moreover, the coagulants were then tested in two mixed-dye solutions, both anionic dyes (RB5/RR120) and anionic/cationic (RB5/MV), resulting in a synergistic effect in the first one and a competitive effect in the secon. Finally, the proposed coagulants were successfully tested on real wastewater samples from an untreated textile dyeing industry. Therefore, the coagulants presented in this work for the removal of several dyes are also capable of being used for wastewater treatment. Full article

The rapid development of the global energy industry has driven an escalating worldwide demand for lithium resources. As a major lithium source, salt lake brines contain abundant divalent ions that hinder efficient lithium extraction. Compared with conventional lithium recovery technologies, nanofiltration membranes emerge as an energy-efficient and environmentally friendly alternative. Over the past decade, interfacial polymerization has been widely adopted to fabricate nanofiltration membranes for lithium–magnesium separation, with studies confirming the superior performance of positively charged membranes in distinguishing monovalent and divalent cations. This review systematically summarizes recent advancements in positively charged nanofiltration membranes synthesized via interfacial polymerization for lithium–magnesium separation, categorizing the design strategies into five distinct approaches. The correlations between intrinsic membrane structural characteristics and separation performance are critically analyzed. Furthermore, current challenges and future research directions are discussed to provide new perspectives for developing high-performance positively charged composite nanofiltration membranes. This work aims to inspire innovative designs and accelerate the practical implementation of nanofiltration technology in lithium extraction from salt lake brines. Full article

Lead (Pb) is a pervasive neurotoxicant with well-documented detrimental effects on the central nervous system, particularly in vulnerable populations such as children. Despite historical recognition of its toxicity, Pb exposure remains a significant public health concern due to its environmental persistence, historical industrial use, and ongoing applications in modern technologies. This review focuses on the mechanisms by which Pb disrupts glutamatergic signaling, a critical pathway for learning, memory, and synaptic plasticity. Pb’s interference with glutamate receptors (ionotropic NMDA and AMPA, as well as metabotropic receptors), transporters (EAATs, VGLUTs, and SNATs), and metabolic pathways (glutamate–glutamine cycle, TCA cycle, and glutathione synthesis) are detailed. By mimicking divalent cations like Ca²⁺ and Zn²⁺, Pb²⁺ disrupts calcium homeostasis, exacerbates excitotoxicity, and induces oxidative stress, ultimately impairing neuronal communication and synaptic function. These molecular disruptions manifest cognitive deficits, behavioral abnormalities, and increased susceptibility to neurodevelopmental and neurodegenerative disorders. Understanding Pb’s impact on glutamatergic neurotransmission offers critical insights into its neurotoxic profile and highlights the importance of addressing its effects on neural function. Full article

Riboswitches regulate gene expression through intricate dynamic conformational transitions, with divalent cation Mg²⁺ and their ligands playing pivotal roles in this process. The dynamic structural mechanism by which the S-adenosyl-L-methionine (SAM) responsive SAM-VI riboswitch (riboSAM) regulates the downstream SAM synthase gene translation remains unclear. In this study, we employed position-selective labeling of RNA (PLOR) to incorporate Cy3-Cy5 into designated positions of riboSAM, applying single-molecule Förster resonance energy transfer (smFRET) method to track its conformational switches in response to Mg²⁺ and SAM. smFRET analysis revealed that in the absence of Mg²⁺ and ligand, riboSAM predominantly adopted a translation-activating apo conformation. Physiological concentrations of Mg²⁺ induced riboSAM to fold into dynamic transit-p and holo-p states, creating a transient and structurally pliable binding pocket for ligand binding. SAM binding locks the dynamic transit-p and holo-p states into their final stable transit and holo conformations through conformational selection, turning off downstream cis-gene expression and completing feedback regulation of cellular SAM concentration. The observed synergistic regulatory effect of Mg²⁺ ions and ligand on riboSAM’s conformational dynamics at single-molecule resolution provides new mechanistic insights into gene regulation by diverse riboswitch classes. Full article

The crystal–chemical behavior of two layered titanosilicate minerals with porous crystal structures, kupletskite, K₂NaMn₇²⁺Ti₂(Si₄O₁₂)₂O₂(OH)₄F, and kupletskite-(Cs), Cs₂NaMn₇²⁺Ti₂(Si₄O₁₂)₂O₂(OH)₄F, was investigated under high-temperature conditions using single-crystal and powder X-ray diffraction; infrared and optical absorption spectroscopy and electron-microprobe analysis. Both minerals undergo topotactic transformation to dehydroxylated and oxidized high-temperature (HT) modifications at temperature above 500 °C while maintaining the basic bond topology of the astrophyllite structure-type. The high-temperature structures show contraction of the unit-cell parameters similar to that of Fe²⁺-dominant astrophyllite, indicating that Mn²⁺ oxidizes along with Fe²⁺ in M(2)–M(4) sites. The oxidation of Mn²⁺ is confirmed by the increase of the Mn³⁺-related absorption (in optical spectra) that is inversely correlated with the intensity of O–H bands in the infrared spectra. The Fe,Mn-oxidation is also evident by the contraction of the M(2), M(3), and M(4)O₆ octahedra. The M(1)–O bond length increases slightly, indicating a preference for mono- and divalent cations to occupy the M(1) site in the heated structure; this may be due to site-selective oxidation and/or migration of unoxidized cations (as previously shown for lobanovite) to this site. The role of extra framework A-site cations (K, Cs) in thermal expansion of these minerals is discussed. Full article

CO₂-switchable surfactants, applicable for mitigating CO₂ geological storage efficiency challenges, offer promising control over foam stability under reservoir conditions, but their performance under extreme pressure, temperature, and salinity still needs thorough investigation. This study experimentally characterizes the performance of CO₂-switchable surfactants by evaluating their interfacial tension (IFT) reduction, foamability, and foam stability under reservoir-relevant conditions. Six surfactants, including cationic (cetyltrimethylammonium bromide (CTAB) and benzalkonium chloride (BZK)) and nonionic amine-based surfactants (N,N-Dimethyltetradecylamine, N,N-Dimethyldecylamine, and N,N-Dimethylhexylamine), were assessed using synthetic brine mimicking a depleted North Sea oil reservoir. A fractional factorial design was employed to minimize experimental runs while capturing key interactions between surfactant type, temperature, salinity, and divalent ion concentrations. Foam switchability was analyzed by alternating CO₂ and N₂ injections, and interfacial properties were measured to establish correlations between foam generation and IFT. Experimental findings demonstrate that cationic surfactants (BZK and CTAB) exhibit CO₂-switchability and moderate foam stability. Nonionic surfactants show tail length-dependent responsiveness, where D14 demonstrated the highest foamability due to its optimal hydrophilic–hydrophobic balance. IFT measurements revealed that BZK consistently maintained lower IFT values, facilitating stronger foam generation, while CTAB exhibited higher variability. The inverse correlation between IFT and foamability was observed. These insights contribute to the development of tailored surfactants for subsurface CO₂ storage applications, improving foam-based mobility control in CCS projects. Full article

The development of highly effective natural-based adsorbents to face the increasing rates of CO₂ production and their delivery to the atmosphere are a big concern nowadays. For such purposes, synthetic and natural zeolites were modified via an ion exchange procedure to enhance the CO₂ uptake. Samples were characterized by SEM, EDS, TGA and nitrogen adsorption at 77 K, showing the correct incorporation of the new metals; in addition, the CO₂ adsorption isotherms were determined using a gas analyser. During the first stage, the role of the compensation cations for CO₂ adsorption was assessed by modifying a pure ZSM-5 synthetic zeolite with different metal precursors present in salt solutions via an ion exchange procedure. Then, five samples were studied; the samples modified with bivalent cation precursors (Zn²⁺ and Cu²⁺) presented a higher adsorption uptake than those modified with a monovalent cation (Na⁺ and K⁺). Specifically, the substitution of the compensation cations for Cu²⁺ increased the CO₂ capture uptake without affecting the surface properties of the zeolite. The results depict the prevalence of π-cation interactions enhanced by the field gradient induced by divalent cations and their lower ionic radii, if compared to monovalent ones. Subsequently, a natural zeolite was modified considering the best results of the previous phase. This Surface Response Methodology was implemented considering 11 samples by varying the concentration of the copper precursor and the time of the ion exchange procedure. A quantitative quadratic model to predict the adsorption uptake with an R² of 0.92 was obtained. The results depicted the optimal conditions to modify the used natural zeolite for CO₂ capture. The modification procedure implemented increased the CO₂ adsorption capacity of the natural zeolite more than 20%, reaching an adsorption capacity of 75.8 mg CO₂/g zeolite. Full article

Spinel ferrites have emerged as fascinating materials, not just for their diverse functionalities, but for the dynamic structural transformations they undergo under varying conditions. These phase transitions, often subtle yet deeply influential, play a pivotal role in tuning their electronic, magnetic, and vibrational properties. At the heart of this complexity lies the versatile arrangement of divalent and trivalent cations between the tetrahedral (A) and octahedral (B) sites, giving rise to a rich spectrum of magnetic interactions, charge dynamics, and lattice responses. This intricate cation interplay makes spinel ferrites a playground for exploring structure–property relationships in advanced functional materials. In this study, we investigated the structural, vibrational, and magnetic properties of Cd ferrite using advanced hybrid functionals (B3LYP, HSE06, and PBE0). Our calculations reveal that the normal spinel phase is the most stable configuration, with minimal energy differences between spin arrangements (~0.005–0.008 eV) and slightly larger differences when including zero-point energy (~0.023 eV). All the investigated structures exhibit a semiconducting nature, with band gaps varying depending on the spin arrangements. The IR and Raman spectra highlight the influence of spin ordering on vibrational modes. The simulations of the Raman spectra demonstrate that both the frequencies and intensities of the Raman peaks strongly depend on the magnetic ordering. The present theoretical study offers a consistent framework for assigning vibrational modes, which may help resolve ambiguities and contribute to a deeper understanding of the vibrational properties of Cd ferrite. These findings provide a robust foundation for further experimental and computational exploration of this material. Full article

A treatment-experienced, highly adherent person living with HIV for over 25 years developed resistance mutations against all four major ART classes, including bictegravir (BIC). This led to viral failure on a quadruple regimen including BIC and doravirine (DOR). Resistance emergence was associated with M184V, thymidine analog mutations (TAMs), NNRTI mutations (108I, 234I, 318F), and INSTI mutations (T97A, G140S, Q148H, G149A), likely driven by suboptimal BIC levels due to divalent cation interactions. During a two-month ART interruption, the resistant virus was rapidly replaced by an ancient wild-type strain. Despite resistance to all four ART classes, a genotype-adapted salvage regimen, including fostemsavir, achieved viral suppression within seven months. Full article

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKP) is a multidrug-resistant (MDR) gram-negative bacterium frequently involved in hospital-acquired pneumonia. The infection caused by this superbug has spread quickly in health centers worldwide, leading to high mortality rates. Due to this emerging scenario, the World Health Organization has categorized CRKP as the highest-priority species for the development of new compounds. In this context, antimicrobial peptides (AMPs) stand out as prototypes for alternative antimicrobials against superbugs, including CRKP. Objectives: We aimed to describe the antibacterial effect of an AMP (LyeTx I), derived from the venom of the spider Lycosa erythrognatha, against CRKP in vitro and in a murine pneumonia model. Results: LyeTx I showed antibacterial effects against all the CRKP clinical isolates tested, with a minimum inhibitory concentration (MIC) range of 2–8 µM and a minimum bactericidal concentration (MBC) range of 2–16 µM. The microbial anionic membrane was the primary target of LyeTx I, which acts by displacing divalent cations bound to this structure in a manner similar to that of polymyxins. Notably, LyeTx I displayed significant lytic activity against mimetic membranes, indicating its potential to disrupt bacterial cell integrity. In in vivo assays, the LyeTx I peptide proved to be safe at a dose of 10 mg/kg. In addition, intraperitoneal use of LyeTx I reduced the bacterial load and inflammation in the lungs of animals infected with a hypervirulent strain of CRKP. Conclusions: These results indicate that LyeTx I is a potential prototype for the development of new antibacterials against MDR species, such as CRKP. Full article

The growing threat of multidrug-resistant bacteria requires innovative therapies beyond traditional antibiotics. This review highlights the potential of endolysin biocomposites using alginate oligosaccharides (AOSs) and modified cellulose (CL) as stabilizers. AOSs could enhance endolysin stability and potentially support colonic fermentation, producing short-chain fatty acids that may synergize with endolysins to combat pathogens and improve gut health. KZ144 and LysPA26 are proposed as optimal candidates for their broad pH range, divalent cation tolerance, and potential effectiveness against Gram-positive and Gram-negative pathogens. Integrating AOSs and CL into biocomposites could offer a novel dual-action strategy against gastrointestinal diseases while potentially reducing antibiotic dependence. Full article

Metal cations are often used to regulate montmorillonite, but the mechanism is still unclear. In this paper, the regulation of different cations in montmorillonite was studied, and it was found that the regulation of different cations had significant effects on the structure of montmorillonite. Firstly, the viscosity is negatively correlated with particle size, and the order of particle size is trivalent > divalent > monovalent cation. Secondly, the swelling capacity is positively correlated with the absolute value of zeta potential, and the order of the zeta potential is monovalent > trivalent > divalent cation. Thirdly, the smaller hydrated ion radius and static electricity of monovalent cations significantly reduce the layer spacing. Meanwhile, isomorphism displacement results in a significant increase in the proportion of cis-vacant configuration due to changing the electronegativity of the octahedron. The comprehensive performance is that the particle size is significantly reduced and the absolute value of zeta potential is significantly increased. It is easy to peel off and expand in water to form a uniform and stable colloidal substance, which has the best gel performance. The research results can provide theoretical support for the regulation of montmorillonite structure and gel properties by different valence metal cations. Full article

Adsorption is a popular method for the recovery of low-grade lithium. It is a low-cost and highly efficient way to treat solutions with low lithium concentrations. The impurity content determines the industrial application. This study investigated a novel strategy to remove divalent cations from a desorption solution containing Mg²⁺, Ca²⁺, and Mn²⁺, generated by a manganese absorbent using an organophosphoric acid, followed by precipitation of lithium carbonate from the concentrated raffinate by evaporation. Di(2-ethylhexyl)phosphoric acid (P204) was selected as the preferred extractant. The saponification method and degree of saponification were determined, and the extraction parameters (pH, extractant concentration, and phase ratio) were investigated. A three-stage countercurrent extraction process was tested. Removal efficiencies of Mg²⁺, Ca²⁺, and Mn²⁺ from the manganese-containing desorption solution exceeded 99%, leaving <1.0 mg/L divalent cations in the raffinate. The raffinate was evaporated and concentrated to >23 g/L lithium. The total concentration of divalent cations in the lithium-rich solution was approximately 10.0 mg/L. Further conversion with sodium carbonate was carried out to prepare a battery-grade lithium carbonate product with a purity of 99.83%. The present work may provide a novel means of lithium recovery from a manganese-containing desorption solution. Full article

The co-occurrence of microplastics (MPs) and antibiotics as emerging contaminants demonstrates significant ecological perturbations in soil matrices. Of particular scientific interest is the potential for MPs to mediate the environmental fate and transport dynamics of co-existing antibiotics. This study investigated MP-mediated ciprofloxacin (CIP) adsorption in lateritic soils. Batch experiments with polyethylene (PE), polypropylene (PP), and poly (ethylene-terephthalate) (PET) revealed soil components dominated CIP retention, while 10% (w/w) MPs reduced soil adsorption capacity by ≥10.8%, with inhibition intensity following PET > PE > PP. Adsorption thermodynamics exhibited significant pH dependence, achieving maximum sorption efficiency at pH 5.0 (± 0.2), which was approximately 83%. Competitive adsorption analysis demonstrated inverse proportionality between ionic strength and CIP retention, with trivalent cations exhibiting superior competitive displacement capacity compared to mono- and divalent counterparts. Isothermal modeling revealed multilayer adsorption mechanisms governed by hybrid chemisorption/physisorption processes in both soil and MP substrates. Spectroscopic characterization suggested differential adsorption pathways: MP-CIP interactions were primarily mediated through hydrophobic partitioning and π-π electron coupling, while soil–MP composite systems exhibited dominant cation exchange capacity and surface complexation mechanisms. Notably, electrostatic attraction/repulsion forces modulated adsorption efficiency across all experimental conditions, particularly under varying pH regimes. This work advances understanding of co-contaminant dynamics in soil ecosystems, informing risk assessment frameworks. Full article