Ions In Solution Research Articles

Hybrid organic - inorganic filter system for cadmium ions adsorption from aqueous solutions

The study reflects on the problem of heavy metals, namely cadmium, polluting the natural environment. The goal was to select the most efficient adsorber enabling ion exchange between calcium and cadmium in an aqueous environment and subsequently design a material hybrid organic-inorganic, particle-fiber system that adsorbs cadmium from aqueous environments and will be easily included in the technological process. The novelty of this study lies in the use of waste food material – eggshells as a source of biogenic nanoparticles. These are applied to a nanofibrous structure made of polyvinyl butyral in amounts of 8 to 10 %wt by weight by the AC electrospinning. (The experiment was performed with these boundary conditions: temperature was 23°C, and humidity was 42%. The high-electrical voltage amplifier generated a sinusoidal waveform with a frequency of 50 Hz and an amplitude of 32 kV) and were used for ion exchange. In ion exchange, cadmium ions are exchanged with calcium ions based on the principle of chemical similarity of the two elements expressed by the z/r ratio (charge/ radius ratio), the z/r ratio is 2.02 for calcium ions Ca2+ and 2.06 for cadmium Cd2. Separateted nanoparticles of calcium carbonate obtained by burning eggshells (727°C) with dimensions from 100 to 200 nm and a specific surface area of 3.9 m2/g showed the highest adsorption capacity of 99.8%, synthetic calcium carbonate at 71.8%, and ground eggshells the lowest at 25.0%. Designed and laboratory-tested filter system of nanoparticles - nanofibers captures 95.6% and 96.8% of cadmium ions from an aqueous solution within 10 minutes and 90 minutes, respectively, at a concentration of cadmium ions of 10 mg/l, and at several nanoparticles of 0.3 g. The ion exchange is carried out only on the filter surface, and after a specific time, the calcium carbonate nanoparticles are released from the filter probably due to absence of chemical bond between nanoparticles and nanostructures or the low density of the nanofibrous structure. SEM, EDX, FTIR, BET and TGA analysis were used for material evaluation. The adsorption capacity of used nanoparticles and filter adsorbers was evaluated according to residual amounts of cadmium ions in aqueous solutions using ICP-IOS.

Investigating adsorption and removal of divalent Ca2+ and Pb2+ ions from aqueous solutions by gamma-irradiation using quartz tuning fork (QTF) sensor technique

In this study, gold-coated quartz tuning forks (QTFs) sensing devices functionalized with self-assembled monolayers (SAM) of a lower-rim functionalized calix[4]arene methoxy ester were used for the detection of divalent Ca2+ and Pb2+ ions in aqueous solutions by utilizing adsorption behavior and the radiative effect. The gold-coated QTF functionalized calix[4]arene methoxy ester sensing device was tested by measuring the respective frequency shifts obtained using small (60 µL) samples of aqueous PbCl2 at two different concentrations (10−6 and 10−4 M). For 10−4 M solutions of PbCl2, results showed that the resonance frequency shift Δf = 317 Hz, from 32,867 Hz (fCalix) to 32,550 Hz (fCalix⊃Pb2+) due to the absorption of lead (Pb2+) ions (10-4 M) by calixl[4]arene methoxy ester receptor molecules on the QTF sensing layer from the aqueous solution to forming the ([Calix ⊃ Pb2+]) complex. The most significant frequency changes were observed at a concentration of 10−6 M CaCl2, where CaCl2 exhibited the biggest change of 356 Hz, from 32,893 Hz (fCalix) to 32,537 Hz (fCalix⊃Ca2+), compared to 317 Hz for PbCl2 (10−4 M). The limit of detection was 100 femtomolar (fM) for CaCl2 and 245 fM for PbCl2. After that, we irradiated the receptor molecules which was holding Pb2+ ions in the complex ([calix ⊃ Pb2+]) on the QTF sensing layer with a radiation dose ranging from 7.5 to 50 µGy of gamma rays from the Cesium-137 source for 30 min. Interestingly, it was observed that the resonance frequency shift (Δf = 54 Hz) back to 32,604 Hz from 32,550 Hz (f(Calix⊃Pb2+)), which strongly suggests that the Pb2+ ion removed from ([calix ⊃ Pb2+]) complex on the QTF sensing layer due to gamma radiation dose. To follow up on the radiation effect of the ([calix ⊃ Pb2+]) on the QTF sensing layer, we stopped the gamma radiation source and kept it for an additional 10 min to see if there was any resonance frequency. It was noticed that an additional resonance frequency shifted (Δf = 33 Hz) back to 32,637 Hz from 32,604 Hz after stopping the gamma radiation source for 10 min. We assume that the complex ([calix ⊃ Pb2+]) absorbs the gamma radiation and continues the removal of Pb2+ ions from the complex on the sensing layer. A similar phenomenon was also observed for the absorption of lead (Pb2+) ions (10-6 M) by calix[4]arene methoxy ester receptor molecules on the QTF sensing layer from the aqueous solution to forming the ([Calix ⊃ Pb2+]) complex. The resonance frequency shift Δf = 142 Hz, from 32,706 Hz (fCalix) to 32,564 Hz (fCalix⊃Pb2+) due to the absorption of lead (Pb2+) ions (10-6 M) by calix[4]arene methoxy ester receptor molecules on the QTF sensing layer from the aqueous solution to forming the ([Calix ⊃ Pb2+]) complex. Subsequent exposure to gamma radiation, with doses ranging from 7.5 to 50 µGy from a Cesium-137 source over 30 min, prompted a resonance frequency shift (Δf = 37 Hz) back to 32,606 Hz from 32,564 Hz (f(Calix⊃Pb2+)). This shift strongly suggests the removal of Pb2+ ions from the ([calix ⊃ Pb2+]) complex on the QTF sensing layer due to gamma radiation dose. X-ray photoelectron spectroscopy (XPS) analysis confirmed the chemical adsorption of Pb2+ ions onto the gold-coated QTFs functionalized calix[4]arene adsorbent sensing layer surface. Therefore, the technology underlying the calix[4]arene-functionalized sensing device holds promise for diverse industrial applications, supporting potential advancements in water pollution mitigation through the proposed adsorption and irradiation mechanism.

New phenanthridine-based multi-functional chemosensor for selective detection of Th4+ and Hg2+ ions in both aqueous and solid state

A new phenanthridine-based multifunctional chemosensor (L), was synthesised via a green synthetic route and characterised using FT-IR, NMR and HRMS analysis. The sensing application of L towards metal ions in both solution and solid-state was studied using UV–vis and fluorescence spectroscopy, which exhibits dual-sensing behaviour for Th4+ and Hg2+ ions with good recyclability. In aqueous acetonitrile, L showed rapid response for the detection of environmental toxic metal ions and has a very low analytical detection limit of 125.5 pM and 1.94 nM for Th4+ and Hg2+ions respectively, which is remarkably lower than the World Health Organization standard. The cation binding property of the L with Th4+ and Hg2+ions was investigated by Job plot, 1H NMR titration, HR-MS and DFT calculation. The in-situ formed ensemble L-Hg2+ was further applied in the naked-eye detection of Cys (Cystine) and His (Histidine) over other common amino acids. The utility of L for real-time detection of Hg2+ and Th4+ ions was explored in various sources of environmental water samples, test paper strips, fingerprint imaging, fluorescent ink and smartphone-assisted sensing techniques, demonstrating the promising on-site visualization of the probe in controlling the toxicity levels in wastewater sources without resorting to expensive instruments.

Highly stable calcium/phosphorus ion solution for dentin hypersensitivity treatment

Highly stable calcium/phosphorus ion solution for dentin hypersensitivity treatment

Adsorption and dersorption of lead using synthetic hydroxyapatite material

The adsorption of Pb2+ ions in solution by synthetic hydroxyapatite material has been researched. Investigations were conducted into the effects of adsorption time, adsorbent mass, solution pH, and Pb2+ ion concentration. The material's adsorption efficiency to Pb2+ can reach 98.7%. Two adsorption isotherm models, Freunlich and Langmuir, were used to evaluate adsorption isotherms. The pseudo-first-order and pseudo-second-order adsorption kinetic models were used to assess the adsorption process's kinetics. Using the electrolysis approach, Pb2+ ions were successfully desorbed from the adsorbed HAp material while recovering metallic Pb on the cathode surface. Pb recovery efficiency can be as high as 93.84%. After desorption, the HAp material retains its original characteristics and still can adsorb Pb2+ ions with a high efficiency of 95.96%.

Synthesis and spectroscopic studies of triazole-based macroheterocycles containing eudesmane-type sesquiterpenoid moieties

Chiral recognition is one of the most important and fascinating areas in supramolecular chemistry. Chiral macrocycles, especially chiral macrocyclic hosts, having stable structures, adjustable internal cavities to encapsulate and complexation have been developed during the last decade. Attention has been paid on the synthesis of covalently linked of rigid units on the side chain of macrocycles with active binding motifs. In this study, new synthetic protocols has been developed for preparation of optically active triazole-based macrocyclic compounds in which eudesmane-type sesquiterpene lactones act as pendent moieties by the implementation of the copper(I)-catalyzed azid-alkyne cycloaddition strategies. The described protocols provided mild reaction conditions, high yields and high atom- and step-economy. New macrocycles with hanging dihydroisoalantolactone units, different combinations of heteroatoms, and ring sizes in the range of 16–36 atoms were characterized by NMR and UV–vis spectroscopy and mass spectrometry analysis. The molecular structures and intermolecular interactions of two new macrocyclic compounds were elucidated using single-crystal X-ray crystallography. Upon addition of Mg(II) or Zn(II) cations to these novel ligands, using titration experiments we observed the formation of 1:1 (16:Mg2+) complexes and 1:1 to 2:1 (16:Zn2+) complexes, respectively, according to stoichiometry. The result suggests that dihydriisoalantolactone and triazole units within the molecules formed complexes with Mg (II) and Zn (II) ions in solution.

Specific iron binding to natural sphingomyelin membrane induced by non-specific co-solutes

HypothesisSphingomyelin (SPM), a crucial phospholipid in the myelin sheath, plays a vital role in insulating nerve fibers. We hypothesize that iron ions selectively bind to the phosphatidylcholine (PC) template within the SPM membrane under near-physiological conditions, resulting in disruptions to membrane organization. These interactions could potentially contribute to the degradation of the myelin sheath, thereby playing a role in the development of neurodegenerative diseases. ExperimentsWe utilized synchrotron-based X-ray spectroscopy and diffraction techniques to study the interaction of iron ions with a bovine spinal-cord SPM monolayer (ML) at the liquid-vapor interface under physiological conditions. The SPM ML serves as a model system, representing localized patches of lipids within a more complex membrane structure. The experiments assessed iron binding to the SPM membrane both in the presence of salts and with additional evaluation of the effects of various ion species on membrane behavior. Grazing incidence X-ray diffraction was employed to analyze the impact of iron binding on the structural integrity of the SPM membrane. FindingsOur results demonstrate that iron ions in dilute solution selectively bind to the PC template of the SPM membrane exclusively at near-physiological salt concentrations (e.g., NaCl, KCl, KI, or CaCl2) and are pH-dependent. In-significant binding was detected in the absence of these salts or at near-neutral pH with salts. The surface adsorption of iron ions is correlated with salt concentration, reaching saturation at physiological levels. In contrast, multivalent ions such as La3+ and Ca2+ do not bind to SPM under similar conditions. Notably, iron binding to the SPM membrane disrupts its in-plane organization, suggesting that these interactions may compromise membrane integrity and contribute to myelin sheath damage associated with neurological disorders.

Tetrapyrrolic macrocycles self-organization into floating layers and sensory properties of their Langmuir-Schaefer films

The influence of the chemical structure of the 5,10,15,20-tetraphenylporphyrin (I) and 2-aza-21-carba-5,10,15,20-tetraphenylporphyrin (II) on their supramolecular organization in floating layers at the air/water interface and sensor properties in Langmuir-Schaefer films has been investigated. It was shown that a minor change in the macrocycle structure (namely, the replacement of a single nitrogen atom from the center to the periphery of macrocycle) has a considerable effect on the surface properties and hysteresis processes of the floating layers. Using the Bruster angle microscopy, it was established that both porphyrins aggregate even before the compression of their floating layers begins. The aggregation is more pronounced in porphyrin I. The analysis of hysteresis loops showed that the formation of a floating layer by the modified porphyrin II requires approximately 100 times more energy than for the unmodified porphyrin I. Using the Langmuir-Schaefer (LS) method, the floating layers were transferred onto solid substrates and the resulting thin films were analyzed by atomic force microscopy, scanning electron microscopy, polarization optical microscopy, and spectrophotometry. The combination of these methods revealed a general tendency of the porphyrins to form 3D structures on the surface of LS-films. The study of the basic properties of the porphyrin's LS-films showed that both porphyrins are diprotonated. The protonation process in porphyrin II occurs at a concentration of HClO4 that is 1000 times lower than that observed in porphyrin I. The greater tendency to protonation of porphyrin II is caused by the availability of both nitrogen atoms (the external nitrogen atom located at the macrocycle periphery and the internal nitrogen atom, which becomes more assesible to interactions due to the distortion of the macrocycle). As for the sensor properties of LS-films for iodide ion in aqueous solutions, it was observed that the diprotonated form of porphyrin I exhibited higher sensitivity due to a more developed film surface because of the presence of a greater number of 3D aggregates. The data obtained can be used in the development of efficient pH-controlled thin-film sensor materials for halide ions.

Development of sensitive napthaquinone-pyridine hydrazone based chemosensor for the colorimetric detection of Cu2+ ion in an aqueous solution

A novel naphthoquinone-pyridine hydrazone (NQPH) based chemosensor was synthesized through the condensation reaction of 2-hydroxynaphthoquinone aldehyde and 2-pyridine carboxylic acid hydrazide. The aqueous buffered solution of NQPH quickly changes color from orange to green upon addition of Cu²⁺ ions with appearance of new absorption band at 452 nm. The UV–vis titration indicated binding constant (K) of chemosensor NQPH with Cu²⁺ was determined to be 2.5 × 104 M⁻¹ (log K = 5.39), and the detection limit for Cu²⁺ ions was found to be 4.35 µM. Analysis using a Job plot based on UV–vis data, along with mass spectrometry, indicated a 1:1 stoichiometry between NQPH and Cu²⁺. Density Functional Theory (DFT) calculations were used to determine the minimum energy conformations, molecular properties and vibrational frequency analysis of NQPH and its Cu²⁺ complex. The DFT results showed the reduction in the HOMO-LUMO gap when NQPH interact with Cu²⁺, indicating intramolecular charge transfer (ICT). The practical application of NQPH was demonstrated by creating test strips for the naked-eye detection of Cu²⁺ and by measuring Cu²⁺ in real water samples.

Comparative Analysis of Cystamine and Cysteamine as Radioprotectors and Antioxidants: Insights from Monte Carlo Chemical Modeling under High Linear Energy Transfer Radiation and High Dose Rates.

This study conducts a comparative analysis of cystamine (RSSR), a disulfide, and cysteamine (RSH), its thiol monomer, to evaluate their efficacy as radioprotectors and antioxidants under high linear energy transfer (LET) and high-dose-rate irradiation conditions. It examines their interactions with reactive primary species produced during the radiolysis of the aqueous ferrous sulfate (Fricke) dosimeter, offering insights into the mechanisms of radioprotection and highlighting their potential to enhance the therapeutic index of radiation therapy, particularly in advanced techniques like FLASH radiotherapy. Using Monte Carlo multi-track chemical modeling to simulate the radiolytic oxidation of ferrous to ferric ions in Fricke-cystamine and Fricke-cysteamine solutions, this study assesses the radioprotective and antioxidant properties of these compounds across a variety of irradiation conditions. Concentrations were varied in both aerated (oxygen-rich) and deaerated (hypoxic) environments, simulating conditions akin to healthy tissue and tumors. Both cystamine and cysteamine demonstrate radioprotective and strong antioxidant properties. However, their effectiveness varies significantly depending on the concentration employed, the conditions of irradiation, and whether or not environmental oxygen is present. Specifically, excluding potential in vivo toxicity, cysteamine substantially reduces the adverse effects of ionizing radiation under aerated, low-LET conditions at concentrations above ~1 mM. However, its efficacy is minimal in hypoxic environments, irrespective of the concentration used. Conversely, cystamine consistently offers robust protective effects in both oxygen-rich and oxygen-poor conditions. The distinct protective capacities of cysteamine and cystamine underscore cysteamine's enhanced potential in radiotherapeutic settings aimed at safeguarding healthy tissues from radiation-induced damage while effectively targeting tumor tissues. This differential effectiveness emphasizes the need for personalized radioprotective strategies, tailored to the specific environmental conditions of the tissue involved. Implementing such approaches is crucial for optimizing therapeutic outcomes and minimizing collateral damage in cancer treatment.

Excited-state intramolecular proton transfer (ESIPT) salicylaldehyde Schiff bases: ratiometric sensing of ammonia and biologically relevant ions in solution and solid state

ABSTRACT The intricate molecular architecture of ESIPT salicylaldehyde Schiff bases facilitates dynamic processes, inducing tunable photoluminescent properties. Notably, their halochromic nature, exhibiting colour changes in response to external stimuli, adds a vibrant dimension to their molecular repertoire. This sensitivity extends to environmental factors, making them valuable indicators for alterations in surroundings. The compound (E)-N’-(3,5-dibromo-2-hydroxybenzylidene)-4-methylbenzohydrazide (PTBH) demonstrates exceptional sensitivity to ammonia, enabling real-time detection (LOD = 0.14 nM) in both solution (ratiometric) and the solid state. Moreover, their metal chelation capability allows simultaneous sensing of Mg2+ and Fe2+ ions, addressing environmental hazards. Exploiting molecular recognition, the fluorescent probe serves as sensors for amino acids, opening new avenues in biomedical diagnostics. The study introduces a novel solid-state emissive Schiff base, highlighting its stimuli-responsive photoluminescent properties and diverse applications, emphasising its potential in intelligent fluorescent materials for analytical and sensing technologies.

DEVELOPMENT OF DRY BUILDING MIXTURES BASED ON REDISPERSIBLE POWDER FOR REGULATING THE PROPERTIES OF PLASTER MIXTURES

The relevance of the work. The results is theoretically substantiated and experimentally confirmed the possibility of obtaining a dry additive-retarder of gypsum setting based on lime and polyvinyl acetate dispersions due to the formation of polyvinyl alcohol and salts of calcium acetate in the result of alkaline hydrolysis of polyvinyl acetate dispersion (PVAD) with the slaked lime in hydrated lime. The results of the work implemented in the production of dry gypsum mixes. Purpose. The development of dry building mixes based on gypsum and time increase of time of their conformance through adding of complex additives on the basis of burnt lime and polyvinyl acetate dispersions [PVAD]. Methodology. The study used standard research techniques to determine physical and mechanical properties of gypsum binders and quality of complex additives according to ДСТУ Б В.2.7-82:2010, ДСТУ Б В.2.7-23-95, ДСТУ Б В.2.7-171:2008. Study of phase composition of materials, micro – and macrostructure was carried out by x-ray diffraction, electron and light microscopy. The results. The influence of the main components of the additive (polyvinyl acetate dispersion and lime) on the properties of hemihydrate gypsum is investigated. The chemistry of the interaction of components of the complex additive, according to which the result of alkaline hydrolysis of polyvinyl acetate is formed: polyvinyl alcohol, a feature of its molecules structure is the presence of hydrophilic OH−groups and the hydrophobic component − a hydrocarbon radical. The hydrophilic part of the molecule being ion adsorbed on the surface of the particles of the binder, forms a monomolecular layer that is oriented with the hydrophobic part of the gypsum particles. It is also possible the formation of calcium acetate Ca(СН3СОО)2, which increases the concentration of calcium ions in solution. The combined effect of hydrolysis products significantly reduce the solubility of hemihydrate, the rate of formation of crystallization centers, due to the slowing effect of these supplements.

Structural and synthesis study of eight isostructural coordination polymers formed by 5-sulfoisophthalic acid and lanthanide ions

This work presents the synthesis and structural characterization of eight isostructural 1D coordination polymers formed by the coordination of 5-sulfoisophthalic acid with various lanthanides ions: Ln = CeIII,PrIII,SmIII,GdIII,DyIII,HoIII,Er(III)andTm(III). The structures were synthetized via a two-step process, wherein a solution of lanthanide ions was added to a mixture of 5-sulfoisophthalic acid and 1,3-bis(4-pyridyl)propane, the latter serving as an auxiliary ligand. This method has proven to be a simpler approach compared to those described in the literature. The compounds were characterized by X-ray single crystal diffraction, FT-IR and Raman spectroscopy, and elemental analysis. Structural analysis revealed a significant correlation between atomic number of the lanthanide ion, unit cell parameters, and space group. On the other hand, the Hirshfeld surface analysis and the two-dimensional fingerprint plot revealed that the set of the intermolecular forces remains unchanged across different lanthanide ion.

The solid-solution HxPO4@Fe3O4 synthesized by irradiation enhances the adsorption capacity of tungsten(VI) and anti-interference of coexisting oxoanion in waste water: Surface oxolation interaction

Tungsten (W), mainly existing as hexavalent oxidation state in nature, has been considered as an increasingly prominent waterborne pollutant, but it is also a critical metal. Therefore, it is important to develop a material to adsorb W(VI) from the waste water containing W(VI) to realize the high-efficiency enrichment and recovery of W(VI). Inspired by self-assembly of phosphate and W(VI) ions in the acidic solutions to form phosphotungstic polyoxoanions (e.g., Keggin-type PW12O403−), in this work, we have loaded the phosphate ion to surface of the magnetic Fe3O4 nanoparticles (Fe3O4 NPs) by β particle irradiation to synthesize a composite adsorbent, HxPO4@Fe3O4 solid-solution (SS). This novel adsorbent is very efficient for W(VI) adsorption and recovery. The results of a batch of adsorption experiments indicate that HxPO4@Fe3O4 SS has a high adsorption efficiency for W(VI) in aqueous environments and strong anti-interference of coexist ions especially PO43−. Under room temperature conditions (∼25 °C), the maximum adsorption capacity reaches 88.44 mg g−1. This method not only ensures a substantial increase in W(VI) adsorption but also provides a facile means for adsorbent recovery, while minimizing additional environmental burdens. Based on the characterization results from Fourier transform infrared, Zeta potential, and X-ray photoelectron spectroscopies, we speculated that the possible mechanism of the adsorption process is that formed W(VI) polyoxoanions in acidic solutions are initially attracted by electrostatic attraction to the positively charged HxPO4@Fe3O4 surface, and then oxolation reaction occurs between W-OH of polyoxoanions and phosphate hydroxyl (P-OH) on the HxPO4@Fe3O4 surface to form P-O-W bridging oxygen group. This adsorption mechanism is also reflected in the adsorption kinetics, following a pseudo-second-order kinetic model, and adsorption thermodynamics, exhibiting a large enthalpy change (−76.3 kJ/mol) and a significant entropy reduction (−174.5 J/(mol K)).

Structure-activity relationship, adsorption, and fenton-like catalytic oxidation capacity of iron-oxide nano-confined materials

In this study, iron-oxide was loaded into polystyrene macroporous microspheres containing sulfonate groups to prepare an environmental purification material with adsorption and Fenton-like oxidizing abilities. Iron-oxide is prone to inactivation due to reunion in the process of preparation and application, and this modification aimed to mitigate this problem. Subsequently, based on the microscopic characterization results and the effect on the treatment of methylene blue (MB) simulated wastewater, the structure-activity relationship of two key (OH− concentrations in precipitation solution and iron ion compositions in the impregnation solution) factors with the adsorption and catalytic oxidation ability of the iron-oxide nano-confined materials were explored. The results indicated that the samples both exhibited adsorption and catalytic oxidation capabilities. The removal efficiency of MB simulated wastewater can reached 95.3% after adsorption for 9 h, reaching 99.98% after catalytic oxidation for 6 h. In addition, the removal efficiency of the MB simulated wastewater exceeded 95% after 6 cycles. The concentration of OH− in precipitation solution could affect the volume of iron crystals on the carrier which affected the pore size of the sample and the adsorption capacity. It also influenced whether iron ions could be stably loaded inside the carrier, determining the conducting homogeneous or heterogeneous Fenton-like reactions and the stability of the samples. The composition of iron ions in the impregnating solution regulated the volume of the crystals and adsorption sites, which influenced the adsorption ability of the samples. In addition, the presence of Fe2+ could promote the progress of Fenton-like reactions. The identification results of the ROSs showed that •OH was the main free radical. The quenching experiment results showed that the contribution rate of •OH toward MB degradation reached 99.81%. In addition, the possible degradation pathways of MB were analyzed.

Revolutionizing sensing technologies: Crafting a green, ultra-sensitive bismuth optical sensor via fixation of 5-(2′,4′-dimethyl-phenylazo)-6-hydroxypyrimidine-2,4-dione on PVC membrane

An innovative and exceptionally responsive optical sensing device engineered to selectively identify Bi(III) ions in water-based solutions. The sensing component, 5-(2′,4′-dimethylphenylazo)-6-hydroxypyrimidine-2,4-dione (DMPAHPD), is incorporated into a plasticized polyvinyl chloride (PVC) membrane. The sensor demonstrates an exceptional selectivity for Bi(III) within a broad dynamic range spanning from 7.5 × 10−10 to 4.2 × 10−5 M at pH 2.25. Notably, it achieves lower quantification and detection limits of 7.25 × 10−10 and 2.15 × 10−10 M, respectively. The optode membrane’s response to Bi(III) proves to be entirely reversible, demonstrating remarkable selectivity for Bi(III) ions over a diverse range of other cations and anions. The sensor exhibits favorable performance characteristics, including good reversibility, a wide dynamic range, a prolonged lifespan, sustained response stability over the long term, and high reproducibility. This visual chemical sensor exhibits potential for real-world usage, offering consistent outcomes when assessing Bi(III) levels in matrices such as water, soil, plants, biological and synthetic mixtures. Importantly, the sensor’s performance is comparable to corresponding data achieved from inductively coupled plasma atomic emission spectroscopy (ICP-AES).

Modeling solvation dynamics of transition metal redox ion through on-the-fly multi-objective Bayesian-optimized force field.

Modeling solvation dynamics and properties is crucial for developing electrolytes for electrochemical energy storage and conversion devices. This work reports an on-the-fly multi-objective Bayesian optimization (OTF-MOBO) method to parameterize force fields for modeling ionic solvation structures, thermodynamics, and transport properties using molecular dynamics simulations. By leveraging solvation-free energy and solvation radii as training data, we employ the data-driven OTF-MOBO algorithm to actively optimize the force field parameters. The modeling accuracy was evaluated in molecular dynamics simulations until the Pareto front in the parameter space was reached through minimized prediction errors in both solvation-free energy and solvation radii. Using transition metal redox ions (Fe3+/Fe2+, Cr3+/Cr2+, and Cu2+/Cu+) in aqueous solution as examples, we demonstrate that simple force fields combining the Lenard-Jones potential and Coulombic potential can achieve relative error below 2% in both solvation free energy and solvation radii. The optimized force fields can be further extrapolated to predict solvation entropy and diffusivities with relative error below 10% compared with experiments.

Influence of wet–dry cycles on the disintegration characteristics of Cretaceous siltstone, China

Cretaceous siltstone, which is widely distributed in the Yichang region, is a type of soft rock characterized by its low strength and its susceptibility to softening and disintegration when exposed to water. To gain a better understanding of the impact of wet–dry cycles on the disintegration characteristics and mechanisms of Cretaceous siltstone, a series of rock disintegration experiments were conducted. These experiments involved microscopic structure analysis and solution ion concentration tests on the specimens. The results of the experiments revealed that with an increase in the number of wet–dry cycles, the Cretaceous siltstone progressively fractured and disintegrated, with larger fragments transitioning into smaller ones. Microscopic structure analysis indicated that continuous wet–dry cycles altered the specimen's microscopic structure, resulting in the formation of new microcracks and pores. The results of solution ion concentration tests showed significant mineral dissolution losses during specimen immersion in the solution. Furthermore, a comparative analysis of various disintegration parameters highlighted that each metric emphasized specific aspects of Cretaceous siltstone disintegration characteristics. Therefore, adopting a multi-metric approach allows a comparison of the validation and assessment of the disintegration features of Cretaceous siltstone from many aspects. Finally, based on the experimental findings, a concise description and summary of the disintegration mechanisms of Cretaceous siltstone under wet–dry cycle conditions are provided; then, combined with its disintegration mechanisms, engineering prevention and control suggestions for timely drainage and a reduction in thermal contact are put forward from the perspectives of waterproofing and heat insulation, which can be used for reference.

On the mechanism and energetics of electrochemical alloy formation between mercury and platinum for mercury removal from aqueous solutions

Mercury pollution is an acute global concern threatening the health of humans and wildlife. Thus, there is a need for new and improved techniques to reduce emissions and remove toxic mercury from aqueous environments. Electrochemical alloy formation, specifically between mercury ions in aqueous solution and a platinum electrode, emerges as a promising solution. Through analysis of reaction mechanisms and energetics related to the formation and dissolution of the PtHg4 alloy, this study aims to deepen our understanding of the underlying processes of effective electrochemical mercury removal. Potentiodynamic measurements indicate rapid alloy formation at a clean platinum surface, proceeding with only trace amounts of metallic mercury on the surface. However, once the electrode surface has sufficient mercury coverage with an alloy thickness of around 1.5 nm, clear evidence of metallic mercury on the surface is observed. Furthermore, the amount of absorbed mercury on the cathode increases linearly in time. The onset potential for the alloy formation is experimentally determined using electrochemical quartz crystal microbalance with dissipation monitoring to be approximately 0.64 V vs. SHE, and the alloy dissolution (oxidation) onset potential is found to be approximately 0.98 V vs. SHE, at a mercury ion concentration of 10 mg/L. Density functional theory calculations are used to provide a theoretical value for the reversible potential from a thermodynamics perspective, yielding a value of 0.78 V vs. SHE at a mercury ion concentration of 10 mg/L. This value is in excellent agreement with the experimental results, suggesting an overpotential of about 0.14 and 0.20 V for the alloy formation and oxidation, respectively. These findings provide important information on the reaction mechanisms and overpotentials of the PtHg4 alloy formation and dissolution, which are key factors for development of large-scale mercury removal based on this technique, as well as fundamental understanding of the electrochemical alloy formation between mercury ions and platinum.

Iota-carrageenan as a regenerating system for Eu3+ recovery: adsorption/desorption cycles

ABSTRACT Renewable and biodegradable polysaccharides attract attention as environmentally friendly adsorbents for the removal of heavy metals from wastewater. One such group, is carrageenan, of which were recently successfully employed to adsorb representative lanthanide and actinide ions. Herein, iota-carrageenan-based hydrogels were used to adsorb europium ions (Eu3+) from water solutions, followed by desorption of the ions from the hydrogel beads and recycling of the beads three times. It was found that sorption yields from a 500 mg/L Eu3+ ion solution with beads that were prepared with 1 or 2 wt/v% aqueous solution of iota-carrageenan with CaCl2 (0.5 M) reached maximum sorption yield of 50% and 65%, correspondingly, after 1 h. In addition, the sorption kinetics followed the pseudo second-order model controlled by chemisorption. Desorption yields in the first cycle using NaNO3 (1 M) with both preparations were 57% and 74%, respectively. The sorption yields increased during the second and third cycles and were efficient in the overall pH range. Cryo-SEM, SEM, SEM-EDS and TGA analyses verified the adsorption and desorption of Eu3+ ions to and from the iota beads and that the Ca2+ ions that initially crosslinked the hydrogel were replaced during the cycles by Eu3+ or Na+ ions. In addition, the beads were stable and easily reusable for several sorption/desorption cycles. Furthermore, after sorption, the beads were characterised by a porous structure, such that beads prepared with a 2 wt/v% aqueous solution of iota-carrageenan yielded a more porous, ordered structure, and after desorption, the bead textures became even more porous.