Search Results (140)

In this research, an analysis of the thermomagnetic properties of a nanoscale spin-2 and spin-3/2 system is conducted. This system is modeled with as a quasi-spherical Ising-type nanoparticle with a diameter of 2 nm, in which atoms with spin-2 and spin-3/2 configured in body-centered cubic (BCC) lattices interact within their relevant nanostructures. To determine the thermomagnetic behaviors of the nanoparticle, numerical simulations using Monte Carlo techniques and thermal bath class algorithms are performed. The results exhibit the effects of exchange couplings ($J_1,J_2^{\prime }$), magnetocrystalline anisotropies ($D_{3/2}^{\prime },D_2^{\prime }$), and external magnetic fields ($h^{\prime }$) on the finite-temperature phase diagrams of magnetization ($M_T$), magnetic susceptibility (${\chi }_T$), and thermal energy ($k_B{T}^{\prime }$). The influences of the exchange, anisotropic, and external field parameters are clearly reflected in the compensation, hysteretic, and pseudocritical phenomena presented by the quasi-spherical nanoparticle. When the parameter reflecting ferromagnetic second-neighbor exchanges in the nanosphere ($J_2^{\prime }$) increases, for a given value of the external magnetic field, the compensation ($T_{comp}$) and pseudocritical ($T_{pc}$) temperatures increase. Similarly, in the ranges $0<J_2^{\prime }⩽4.5$ and $-15⩽h^{\prime }⩽15$ at a specific temperature, an increase in $J_2^{\prime }$ results in the appearance of exchange anisotropies (exchange bias) and and increased hysteresis loop areas in the nanomodel. Full article

Urbanization, escalating agriculture, tourism, and industrial development in the Chiang Mai–Lamphun groundwater basin in northern Thailand have increased water demand, causing widespread groundwater extraction. Over the past few decades, there has been a rapid, unrecoverable steady drop in groundwater levels in several areas in Chiang Mai and Lamphun provinces. This study employed hydrogeological investigations, hydrometeorological data analyses, stable isotopic analysis (δ¹⁸O and δ²H), and groundwater flow modeling using a 3D groundwater flow model (MODFLOW) to quantify groundwater recharge and delineate important groundwater recharge zones within the basin. The results showed that floodplain deposits exhibited the highest recharge rate, 104.4 mm/y, due to their proximity to rivers and high infiltration capacity. In contrast, younger terrain deposits, covering the largest area of 1314 km², contributed the most to total recharge volume with an average recharge rate of 99.8 mm/y. Seven significant recharge zones within the basin, where annual recharge rates exceeded 105 mm/y (average recharge of the entire basin), were also delineated. Zone 4, covering parts of densely populated Muaeng Lamphun, Ban Thi, and Saraphi districts, had the largest area of 330 km² and a recharge rate of 130.2 mm/y. Zone 6, encompassing Wiang Nong Long, Bai Hong, and Pa Sang districts, exhibited the highest recharge rate of 134.6 mm/y but covered a smaller area of 67 km². Stable isotopic data verified that recent precipitation predominantly recharged shallow groundwater, with minimal evaporation or isotopic exchange. The basin-wide average recharge rate was 104 mm/y, reflecting the combined influence of geology, permeability, and spatial distribution. These findings provide critical insights for sustainable groundwater management in the region, particularly in the context of climate change and increasing water demand. Full article

A dysprosium-based metal–organic framework (MOF), namely [DyLH₂O]_n (1) (H₃L = 4-((bis(carboxymethyl) amino)methyl)benzoic acid), was successfully synthesized via the hydrothermal method. According to the structural characterization, metal centers in this complex are linked by four bridges (two oxygens and two carboxylic groups), leading to Dy₂ units. On further connection by single carboxylic groups, the dimeric units extend to form a two-dimensional layer with a 4⁴ topological structure. Finally, the 2D layers were assembled into a 3D framework by the L⁻³ anions. A thermogravimetric test shows that [DyLH₂O]_n can maintain high thermal stability after losing water, until the temperature reaches 426 °C. Magnetic studies on 1 reveal antiferromagnetic exchange interactions of Dy³⁺…Dy³⁺ at low temperatures. Additionally, frequency-dependent out-of-phase signals were observed in alternating current (ac) magnetic susceptibility measurements for 1, indicating that it has slow magnetic relaxation features. Full article

Fluoride-enriched geothermal groundwater poses chronic health risks (e.g., dental and skeletal fluorosis) through prolonged exposure; nevertheless, hydrochemical-driven factors and the genetic mechanism of fluoride enrichment in such systems remain inadequately identified. This study employed hydrochemical characterization, isotopic tracing, and health risk models to elucidate the genetic mechanism of fluoride-enriched geothermal groundwater. The key findings reveal the following. (1) Geothermal groundwater (Cl-Na type; TDS 90–345 mg/L; pH 6.25–7.42) contrasts with alkaline river water (pH 7.48–8.05; SO₄-Na/HCO₃-Na) and saline seawater (TDS 23.9–28.2 g/L). Stable isotopes (δD, δ¹⁸O) confirm atmospheric precipitation recharge with an elevation of 69–635 m. (2) The Self-Organizing Map algorithm categorized 30 geothermal samples into three groups: Cluster I—low temperature and pH, high TDS; Cluster II—high temperature, low F⁻ concentration; and Cluster III—low TDS, and high pH and F⁻ concentration. (3) Fluoride enrichment in Cluster III originated from the evaporite/fluorite dissolution under alkaline conditions and cation exchange interactions, while the inhibition of CaF₂ dissolution by reverse cation exchange limited the accumulation of F⁻ in Cluster II and Cluster III samples. (4) Health risks disproportionately affect children (80% high risk) and women, necessitating pre-use defluorination. Full article

¹³⁷Cs is a persistent β/γ-emitter (t_1/2 = 30.1 years) generated from ²³⁵U and ²³⁹Pu fission. It is a critical challenge to efficiently capture ¹³⁷Cs⁺ for nuclear waste management due to its high solubility, environmental mobility, and propensity for biological accumulation. Herein, we prepare a two-dimensional (2D) thiotitanate Rb_0.32TiS₂·0.75H₂O (denoted Rb-TiS₂) using a special molten salt synthesis method, “Mg + RbCl”. Rb-TiS₂ can selectively capture Cs⁺ from aqueous solutions. Its structure features a flexible anionic thiotitanate layer with Rb⁺ as counter ions located at the interlayer spaces. As an ion exchanger, it possesses high adsorption capacity (q_m^Cs = 232.70 mg·g⁻¹), rapid kinetics (the removal rate R > 72% within 10 min), and a wide pH tolerance range (pH = 4–12) for Cs⁺ adsorption. Through a single-crystal X-ray structural analysis, we elucidated the mechanism of Cs⁺ capture, revealing the ion exchange pathways between Cs⁺ and Rb⁺ in Rb-TiS₂. This work not only provides an important reference for the synthesis of transition metal sulfides with alkali metal cations but also proves the application prospect of transition metal sulfides in radionuclide remediation. Full article

In this study, we studied the process of recovering copper from mine-leached water at an altitude of 4500 m. The process was ion exchange–esolution–nanofiltration–separation–cyclone electrodeposition. As a result, high-purity copper cathodes were produced. The study demonstrated that the maximum adsorption capacity of ion exchange resin D402 for Cu²⁺ reached 174.6 g/L and the efficiency of Cu²⁺ adsorption and eluent was found to be 97.2% and 94.2%, respectively. The results of Fourier Transform infrared spectroscopy (FTIR) analysis indicated that the resin contains -OH and -NH₂. The lone pair electrons on O and N atoms can form coordination bonds with copper ions to form stable complexes. The results of X-ray photoelectron spectroscopy (XPS) analysis indicated that copper ions were absorbed into the resin. The recovery efficiency of Cu²⁺ throughout the entire process reaches 95.1%, and the purity of the resulting copper cathode reaches 99.997%. This method is distinguished by a straightforward process, minimal environmental impact, optimal operating conditions, high copper recovery efficiency, and a high copper grade. Full article

Two new Cu(II) (CP1) and Co(II) (CP2) coordination polymers (CPs) with the triazole ligand 5-methyl-1-(pyridin-4-yl-methyl)-1H-1,2,3-triazole-4-carboxylate (L1) have been synthesized and structurally characterized by SCXRD (Single Crystal X-Ray Difraccion), PXRD (Power X-Ray Difracction), FT-IR (Fourier Transform Infrared), TG (Theermo Gravimetric), and electrochemical techniques. Both CPs were obtained at the water/n-butanol interface by reacting nitrate salts of each metal with the NaL1 ligand. SCXRD analysis revealed that CP1 (Coordination Polymer 1) and CP2 (Coordination Polymer 2) crystallize in the monoclinic space groups C2/c (No. 15) and P2₁/n (No. 14), respectively, forming 1D zigzag chain structures, which further lead to a 2D supramolecular network through O-H⋯O and C-H⋯O hydrogen bond interactions, respectively. In CP1, the supramolecular structure is assembled by hydrogen bonds involving water molecules. In contrast, CP2 forms its supramolecular network mainly through hydrogen bonds between adjacent triazole ligand molecules. Hirshfeld surface analysis revealed that the most significant contributions to the crystal packing come from H⋯O/O⋯H, H⋯H, H⋯N/N⋯H, and H⋯C/C⋯H interactions. In addition, FT-IR provided information on the functional groups involved in the coordination, while the decomposition patterns of both CPs were evaluated by TGA. Electrochemical studies conducted in a saline environment showed that CP1 exhibits superior hydrogen evolution reaction (HER) kinetics compared to CP2, as evidenced by a higher exchange current density and a lower Tafel slope. Density functional theory calculations and experimental bandgap measurements provided a deeper understanding of the electronic properties influencing the electrochemical behavior. The results highlight the potential of CP1 as an efficient catalyst for HER under saline conditions. Full article

Layered double hydroxides (LDH) containing various exchangeable anions were studied to show how X-ray Photoelectron Spectroscopy (XPS) can provide information on the local environments of the different elements within the interlayer anionic groups and their possible influence on the LDH interlayer hydroxide surfaces. As such, XPS can potentially provide additional information about these systems that cannot be obtained by other common spectroscopic methods, such as infrared and Raman spectroscopy. A Mg₆Al₂X(OH)₁₆. 4H₂O with X representing interlayer anions CO₃²⁻, PO₄³⁻, SO₄²⁻, MoO₄²⁻, CrO₄³⁻, Fe(CN)₆⁴⁻, and Fe(CN)₆³⁻ was studied. The hydroxide layer structure is characterized by the Mg 2p and Al 2p with a binding energy of around 50.1 and 74.5 eV for the normal CO₃²⁻ containing LDH. The O 1s contained three peaks related to the layer OH-groups at 531.6 eV, interlayer CO₃²⁻ at 530.5 eV and interlayer water at 532.4 eV. Similar observations were made for the other interlayer anions showing characteristic P 2p, S 2p, and Mo 3d peaks. Intercalation with CrO₄³⁻ shows that a significant amount of the Cr⁶⁺ has been reduced to Cr³⁺. Finally, the intercalation of hexacyanoferrate in hydrotalcite showed the potential of XPS in detecting changes in the oxidation state of Fe upon intercalation in the LDH with a change in the Fe 2p peaks with a shift in binding energy and the possibility of determining the amount of reduction of Fe(III) to Fe(II). In general, the XPS high-resolution scans of P 2p, S 2p, Mo 3d, and Cr 2p show that slightly lower binding energies are observed compared to the binding energy values for the corresponding anionic groups as part of a rigid crystal structure, such as in minerals. Overall, the influence of the nature of the interlayer anion on the binding energy of the elements (Mg, Al, O) in the layered double hydroxide structure is minimal and considered to be within the experimental error of XPS. A detailed analysis of XPS data in combination with infrared and Raman spectroscopy shows how XPS can provide additional information that is not readily available via vibrational spectroscopy. XPS can simultaneously account for both surface and bulk properties of LDH that are not available through common vibrational spectroscopic methods. Full article

It is known that ultrashort echo time (UTE) magnetic resonance imaging (MRI) sequences can detect signals from water protons but not collagen protons in short T2 species such as cortical bone and tendons. However, whether collagen protons are visible with the zero echo time (ZTE) MRI sequence is still unclear. In this study, we investigated the potential of the ZTE MRI sequence on a clinical 3T scanner to directly image collagen protons via D₂O exchange and freeze-drying experiments. ZTE and UTE MRI sequences were employed to image fully hydrated bovine cortical bone (n = 10) and human patellar tendon (n = 1) specimens. Then, each specimen was kept in a 30 mL syringe filled with D₂O solution for two days. Fresh D₂O was flushed every 2 h to reach a more complete D₂O–H₂O exchange. Later, the samples were lyophilized for over 40 h and then sealed in tubes. Finally, the samples were brought to room temperature and visualized using the identical 3D ZTE and UTE sequences. All hydrated bone and tendon specimens showed high signals with ZTE and UTE sequences. However, all specimens showed zero signal after the D₂O exchange and freeze-drying procedures. Therefore, similar to UTE imaging, the signal source in ZTE imaging is water. The ZTE sequence cannot directly detect signals from collagen protons in bone and tendons. Full article

The most commonly used homogeneous catalyst for fatty acid esterification is a corrosive sulphuric acid. However, this requires costly investment in non-corrosive equipment, presents a safety risk, is time consuming, and increases effluent generation. In this study, inorganic 3D heteroborane cluster strong acids are employed for the first time as homogeneous catalysts. Three novel isomeric tetrachlorido and tetrabromido derivatives of 3,3′-commo-bis[undecahydrido-closo-1,2-dicarba-3-cobaltadodecaborate](1−) [1⁻] were synthesised and fully characterised using a range of analytical techniques, including NMR, TLC, HPLC, MS, UV-Vis, melting point (MP), CHN analyses, and XRD. Ultimately, H₃O[8,8′-Cl₂-1⁻] was identified as the most efficient, reusable, and non-corrosive homogeneous catalyst for the esterification of four fatty acids. The reactions are conducted in an excess of alcohol at reflux. The effective absorption of water vapour provided by the molecular sieves maximises acid conversion. The hydrophobic dye Sudan black B was employed as an acid-base indicator to facilitate a comparison of the H₀ acidity function of sulphuric acid and halogenated heteroboranoic acids when dissolved together in methanol. The ²³Na NMR analysis demonstrated that the application of dry methanol resulted in the displacement of Na⁺ ions from zeolite, which subsequently exchanged the H₃O⁺ ions of the acid. This process led to a gradual reduction in the efficiency of the catalysts, particularly with repeated use. The solution to this issue is to regenerate the catalyst on the ion exchanger following each reaction. In contrast to the published methods, our new approach meets 10 of 12 green chemistry principles. Full article

Improving saline soils’ properties by incorporating limes is a practical technique, generally due to cation exchange, pozzolanic reaction, and carbonation. This study explores how soil salinity, measured by electrical conductivity, affects untreated and lime-treated saline soils. An Algerian sebkha soil (from Ain M’lila) with an original high salinity (ECe3 = 23.2 dS.m⁻¹) was used. The same soil was washed to create medium (ECe2 = 8.3 dS.m⁻¹) and low (ECe1 = 2.32 dS.m⁻¹) salinity soil samples. The results of this study indicate that salinity influenced the shape of the particle size distribution curve, particularly in the silt range. Salinity also had a significant effect on carbonate content (CaCO₃) and unconfined compressive strength (UCS). For the untreated soil, when salinity decreased, the UCS and CaCO₃ content increased. However, when salinity decreased for the treated soil, the UCS increased, while the CaCO₃ content decreased. X-ray diffraction (XRD) analysis of untreated soils showed halite (NaCl) disappearance and gypsum (CaSO₄ 2H₂O) reduction with decreasing salinity in ECe1. In treated soil at ECe3, these mineral phases remained constant. While XRD detected no new cementitious phases in treated ECe3 or ECe1 samples, thermogravimetric analysis confirmed the presence of portlandite in both. As Ain M’lila sebkha is a chloride–sulfate soil, the dissolution of the halite and gypsum phases released more Cl⁻ and SO₄²⁻ ions into the interstitial solution. In a low fraction of clay, these ions obstructed and slowed the pozzolanic reaction in the ECe3 soil. Identifying the season when this type of soil has lower salinity can be beneficial for treatment from a technical, economic, and environmental point of view. Full article

In this study, we report the syntheses, crystal structures and magnetic properties of ternary copper(II) coordination compounds with l-homoserine (l-Hhser) and 1,10-phenanthroline (phen). Six new coordination compounds were obtained: [Cu(l-hser)(H₂O)(phen)]₂SO₄·5H₂O (1·5H₂O), [Cu(μ-l-hser)(H₂O)(phen)][Cu(l-hser)(H₂O)(phen)]₃(SO₄)₂∙12H₂O (2·12H₂O), {[Cu(μ-l-hser)(H₂O)(phen)][Cu(μ-l-hser)(phen)]SO₄·6H₂O}_n (3·6H₂O), {[Cu(μ-l-hser)(H₂O)(phen)]₂SO₄·3H₂O}_n (4·3H₂O), [Cu(l-hser)(H₂O)(phen)][Cu(l-hser)(CH₃OH)(phen)]SO₄·4H₂O (5·4H₂O) and {[Cu(l-hser)(CH₃OH)(phen)][Cu(μ-l-hser)(phen)]SO₄·5CH₃OH}_n (6·5CH₃OH). It was shown that slight differences in water content in the synthetic mixtures highly influence the final product, so in some cases, two or three different products were obtained. The compounds were characterized by single-crystal X-ray diffraction and ESR spectroscopy. Crystal packings are based on intensive networks of hydrogen bonds and π interactions. Most water solvent molecules in these microporous compounds are found in discrete pockets (1∙5H₂O, 2∙12H₂O, 3∙6H₂O, 4∙3H₂O). In 5∙4H₂O, water molecules are packed in pockets and 1D channels and in 6∙5CH₃OH methanol solvent molecules form 1D channels. ESR spectroscopy measured from room down to liquid nitrogen temperature was used for local magnetic characterization of copper centers. The spin Hamiltonian parameters obtained from the spectral simulation revealed copper coordination geometry that is in agreement with the structural results. Furthermore, ESR spectra revealed no significant exchange coupling between copper ions. 3·6H₂O showed pronounced antiproliferative activity toward human colon cancer cell lines (HCT116), human breast cancer cell line (MCF-7) and human lung cancer cell lines (H460). Full article

The present study investigated the ¹H Nuclear Magnetic Resonance (NMR) spectra of hydrogen-rich water (HRW) produced using the EVObooster device. The analyzed HRW has pH = 7.1 ± 0.11, oxidation–reduction potential (ORP) of (−450 ± 11) mV, and a dissolved hydrogen concentration of 1.2 ppm. The control sample was tap water filtered by patented technology. A 600 NMR spectrometer was used to measure NMR spectra. Isotropic 1H nuclear magnetic shielding constants of the most stable clusters (H₂O)_n with n from 3 to 28 have been calculated by employing the gauge-including-atomic-orbital (GIAO) method at the MPW1PW91/6-311+G(2d,p) density function level of theory (DFT). The HRW chemical shift is downfield (higher chemical shifts) due to increased hydrogen bonding. More extensive formations were formed in HRW than in control filtered tap water. The exchange of protons between water molecules is rapid in HRW, and the ¹H NMR spectra are in fast exchange mode. Therefore, we averaged the calculated chemical shifts of the investigated water clusters. As the size of the clusters increases, the number of hydrogen bonds increases, which leads to an increase in the chemical shift. The dependence is an exponential saturation that occurs at about N = 10. The modeled clusters in HRW are structurally stabilized, suggesting well-ordered hydrogen bonds. In the article, different processes are described for the transport of water molecules and clusters. These processes are with aquaporins, fusion pores, gap-junction channels, and WAT FOUR model. The exponential trend of saturation shows the dynamics of water molecules in clusters. In our research, the chemical shift of 4.257 ppm indicates stable water clusters of 4–5 water molecules. The pentagonal rings in dodecahedron cage H₃O⁺(H₂O)₂₀ allow for an optimal arrangement of hydrogen bonds that minimizes the potential energy. Full article

In this study, we report highly crosslinked hybrid aerogels with an organic backbone based on vinylmethyldimethoxysilane (VMDMS) with tuneable properties. For an improved and highly reproducible synthesis, a prepolymer based on 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (D₄V₄) and VMDMS as monomers was prepared and purified. Di-tert-butylperoxide (DTBP) concentrations of 1 mol% initiate the radical polymerization of the mentioned monomers to achieve high yields of polymers. After purification, the obtained viscous polyorganosilane precursor could be reproducibly crosslinked with dimethyldimethoxysilane (DMDMS) or methyltrimethoxysilane (MTMS) to form gels in benzylic alcohol (BzOH), water (H₂O) and tetramethylammonium hydroxide (TMAOH). Whereas freeze-drying these silica-based hybrid aerogels led to high thermal conductivity (>20 mW m⁻¹K⁻¹) and very fragile materials, useful aerogels were obtained via solvent exchange and supercritical drying with CO₂. The DMDMS-based aerogels exhibit enhanced compressibility (31% at 7 kPa) and low thermal conductivity (16.5 mW m⁻¹K⁻¹) with densities around (0.111 g cm⁻³). The use of MTMS results in aerogels with lower compressibility (21% at 7 kPa) and higher density (0.124 g cm⁻³) but excellent insulating properties (14.8 mW m⁻¹K⁻¹). Full article

Magnetite-loaded biochar has recently received attention owing to its ability to remove arsenic from contaminated soil. In this study, mulberry stem biochar (MBC) and Fe₃O₄-loaded mulberry stem biochar (Fe₃O₄@MBC) were produced and used in a 100-day incubation experiment to investigate their performance in the stabilization of arsenic in paddy soil severely polluted by the As (237.68 mg·kg⁻¹) mechanism. Incubation experiments showed that Fe₃O₄@MBC was more effective in immobilizing As after incubation for 100 days. Moreover, adding Fe₃O₄@MBC facilitated the transformation of exchangeable heavy metals into organic-bound and residual forms, thereby reducing As available concentrations, mobility, and bioavailability in the soil, and elevating slightly the soil pH and dissolved organic carbon (DOC). The concentration of TCLP-extractable As (As_TCLP) in contaminated soil was reduced from 93.85 to 7.64 μg·L⁻¹ within 10 d, below the safety limit for drinking water set by the World Health Organization (WHO). The characterization results of Fe₃O₄@MBC after incubation indicated that the mechanisms for As passivation are linked to redox reactions, complexation, electrostatic attraction, surface adsorption, and coprecipitation. Conclusively, Fe₃O₄@MBC is a promising amendment in highly As-contaminated soil and provides a theoretical reference in such polluted paddy soil remediation. Full article