Journal of Solution Chemistry最新文献

The distribution of the chemical species of the elements Al, Fe, Zn, Cu, Cd, and Pb in surface waters influenced by coal mining and coal processing industry in Bulgaria was calculated using two chemical equilibrium models—combined ion association—Stockholm humic model (IA-SHM) and biotic ligand model (BLM). It was established similarity in the results of the both models in water with dominant organometallic microelement species. When inorganic species (free ions, hydroxy, and carbonate species) were dominant, differences in species distribution were calculated, the largest for Zn, followed by Cd, Pb, and insignificant for Cu. These differences are due to the mutual competition of metals accounted for by IA-SHM, which makes it more effective for estimating microelement bioavailability. The results point to the absence of free ions of Al and Fe and the presence of insignificant amounts of Cu in all studied waters and of Pb in waters with low alkalinity, which defines a low level of bioavailability for these elements. High free ion contents were calculated for Zn and Cd, which makes them more bioavailable and therefore riskier for aquatic organisms despite their low concentrations. In highly alkaline waters, 15–40% of labile carbonate species of Pb were calculated, which, together with its high concentration, makes it the most hazardous element in these waters.

1-Benzofuran is a heterocyclic compound with fused benzene and furan rings that is used in materials science, nonlinear optics, drug development and pharmacology. This study investigated how solvent polarity and temperature affect vibrational spectra, photophysical properties, and thermodynamic behavior. Using semiempirical, Hartree–Fock, and DFT (B3LYP) methods with basis sets such as 6–31 + G (d,p), 6–311 + G (d,p), and aug-cc-pVDZ, it was found that solvent polarity influenced bond angles, bond lengths, dipole moments, HOMO‒LUMO gaps, and thermodynamic properties. Solvation effects in water were observed in the FT-IR and FT-Raman spectra, with peak shifts due to hydrogen bonding. The electrostatic potential map revealed electrophilic and nucleophilic regions important for receptor binding. The nonlinear optical properties increased significantly with increasing solvent polarity, reaching α = 230.14 a.u. and β = 314.02 a.u. in polar solvents. As the temperature increased from 100 to 1000 K, the heat capacity, enthalpy, and entropy increased, leading to instability. The absorption spectra showed peaks at 240–300 nm in polar solvents, with a bathochromic shift of 5.11 nm. This study offers insights into the photophysical and optical properties of 1-benzofuran in different solvents and at different temperatures.

Graphical Abstract

This work examined the impact of sodium dodecyl sulfate (SDS) surfactant on the oxidation kinetics of D-glucose employing imidazolium fluorochromate (IFC) as the oxidant. The experiments were conducted under pseudo-first-order conditions at 30 °C, with D-glucose in a significantly higher concentration than IFC. The solvent medium used was 50% (v/v) aqueous acetic acid. The reaction demonstrated a first-order dependence on [IFC] and [HClO₄]. The order for [D-glucose] oxidation kinetics was slightly less than one. Perchloric acid acted as a catalyst in this process. The addition of acrylonitrile had no effect on rate constants (k_obs). k_obs decreased with an increase in the concentration of Mn(II) ions. An increase in the dielectric constant of the medium had an inverse effect on k_obs. The initial increase in [SDS] led to a corresponding rise in k_obs, though a saturation in k_obs was observed for elevated [SDS]. The Menger-Portnoy and Piszkiewicz models were used to quantitatively assess the experimental results. The binding constant (K_p), cooperativity index (n), and various thermodynamic parameters in the presence of SDS were calculated. Infrared and mass spectroscopy were used to ascertain D-gluconolactone as the primary product of the reaction. Based on these findings, a reaction scheme has been suggested.

This study investigates the solubility of triethylamine hydrochloride (TEA·HCl) in acetonitrile (ACN) and dimethyl carbonate (DMC) mixtures, crucial for optimizing TEA·HCl separation during vinylene carbonate (VC) synthesis. Solubility was measured experimentally at 0.1 MPa from 308.15 K to 343.15 K across ACN mass fractions (({w}_{1})) from 0.1 to 1.0. Results reveal a positive correlation between TEA·HCl solubility, temperature, and ({w}_{1}). The Jouyban–Acree, Van’t Hoff–Jouyban–Acree, and Apelblat–Jouyban–Acree models were employed to correlate the solubility data. While generally accurate (average ARD ≈ 8.3%), these models exhibited substantial errors at ({w}_{1}) = 0.1 (ARD > 40%). Thermodynamic analysis revealed an endothermic, enthalpy-driven dissolution process. Density Functional Theory (DFT) calculations identified a sharp change in solvation free energy at ({w}_{1}) = 0.1, correlating with the observed solubility deviations and model inaccuracies. This study provides essential solubility data and thermodynamic insights for enhancing TEA·HCl crystallization and separation during VC production, emphasizing the critical role of solvent composition.

The conductivities of aqueous KCl + sucrose solutions were measured at KCl concentrations up to 0.0067 mol dm⁻³ and sucrose concentrations up to saturation, at temperatures from 293.15 K to 313.15 K. The data were correlated and analyzed by using the low-concentration chemical model (lcCM) version of the Fuoss–Justice equation. The calculated Walden products and the (Lambda^{infty }) and (K_{text A}) are in accordance with the previous studies and the results agree well with the Lee–Wheaton model. Eyring enthalpies of activation for charge transport were evaluated. Calculated thermodynamic quantities for ion association ((Delta G^{^circ } ,Delta H^{^circ } ,Delta S^{^circ })) are consistent with the results from other methods (exergonic, endothermic, and enhanced degree of freedom). Splitting the standard Gibbs energy change, into coulombic and non-coulombic terms, shows that the electrostatic contribution is of major importance.

Modelization of adsorption and desorption of phenol from granular activated carbon (GAC) by organic solvent acetone and green solvent limonene and then by mixture of both solvents is investigated in this paper. The results showed that the pseudo-second-order kinetic model more appropriately described the phenol adsorption and desorption. The adsorption isotherms at 20, 30, and 40 °C indicated that the Langmuir model better expressed adsorption, while desorption isotherms revealed that desorption is well fitted by Freundlich model. Following adsorption isotherms, the surface occupied with phenol could be calculated indicating that not the whole surface was covered with phenol molecules due to the acidic surface. The negative ΔH° showed that adsorption (− 0.0144 kJ·mol⁻¹) and desorption (acetone: − 0.0179 kJ·mol⁻¹ limonene: − 0.0174 kJ·mol⁻¹) were exothermic processes. In addition, the negative ΔS° showed that adsorption (− 0.0178 kJ·mol⁻¹·K⁻¹) implies the non-affinity of the surface for phenol; however, the positive ΔS° in desorption (acetone: 0.0157 kJ·mol⁻¹·K⁻¹ limonene: 0.0182 kJ·mol⁻¹·K⁻¹) means an affinity between adsorbent surface and adsorbate. The negative values of free energy ΔG° obtained for adsorption and desorption indicate the feasibility and spontaneous nature of adsorption and desorption process.

Experimental determination of solubility is a time-consuming procedure with relatively high reagent consumption. The solubility of poorly water-soluble compounds in solubilizer solutions can be calculated from the values of their binding constants (also called stability, formation, or association constants) determined by other methods that require less time and reagents for research. For the case of the formation of both 1:1 and 1:2 complexes, comparison of solubility based on binding constant values is impossible without calculations. The paper considers the theoretical relationship of the solubility to the binding constants for this situation, as well as to the intrinsic solubility in the absence of solubilizer in solution. In addition, equations are presented for calculating the solubilizer concentration to obtain the desired solubility. Assumptions and limitations for such calculations are discussed. Demonstrative calculations were carried out using literature data on binding constants, previously determined by the authors using affinity capillary electrophoresis, for betulin 3,28-diphthalate and 3,28-disuccinate with six cyclodextrins: β-cyclodextrin (β-CD), hydroxypropyl-β-CD, randomly methylated β-CD, dimethyl-β-CD, γ-CD, and hydroxypropyl-γ-CD. It was shown that for calculating solubility at high values of binding constants it is important to use not the total concentration of the solubilizer in solution, but its equilibrium concentration. Higher values of the binding constants were found to do not always provide higher solubility. It turned out that the difference in solubilizing capacity between solubilizers may not be too significant at relatively high values of solubility in the absence of a solubilizer.

The processes occurring at the solid–liquid interface of hydroxyapatite ceramic tablets placed in contact with simulated de- and remineralization solutions similar to those in the oral cavity are investigated. A solution containing lactic acid was chosen as a demineralizing agent because it mimics the conditions during bacterial decomposition of sugars. A two-stage remineralization procedure was applied—treatment with a solution of polycarboxybetaine, followed by a stay in artificial saliva. The results show that the demineralisation causes changes in the quantitative ratios of the major elements on the surface, but not in their chemical environment. The mechanism of the dissolution depends on the time. It starts with a higher rate in the center and a lower rate in the periphery. The two speeds equalize over time. During the remineralization procedure, as an effect of the interaction with the solution’s components, new surface species like Ca–OH and Na–O–P are formed and the quantity of O–H(C–O) and C–O(C–N) increases. Since the Raman spectra do not show the presence of any phase other than hydroxyapatite, we assume that remineralization occurs through the growth of HA crystals.

Hydroxamic acids (N-hydroxyamides) are relevant as ligands for metal ions, which are usable in agriculture and medicine and also present in nature. Their acidity constants in aqueous systems are needed to rationalize their metal ion complexation behaviour and parametrize-related prediction models. In this study, a detailed methodology is presented for determining the acidity constants (pK_a values) in water using a combination of nuclear magnetic resonance (NMR) spectroscopy with potentiometry. It includes the acidity constants of five N-hydroxyamides, two N-hydroxyimides and three other compounds: 1H-1,2,3-benzotriazole, 4-hydroxy-3-methoxybenzoic acid (vanillic acid) and pyrrolidine-2,5-dione (succinimide). Besides directly measured absolute pK_a values of the individual compounds, relative acidity (∆pK_a) measurements between pairs of compounds were carried out as well, resulting in a pK_a “ladder”, i.e. a system, where all acids were linked together by ΔpK_a measurements. The absolute and relative measurement results were combined together to improve the results’ reliability. As a result, twelve reliable pK_a values are now available, of which three have not been reported previously.

This study focuses on the analysis of the absorption spectra of cobalt(II) nitrate and cobalt(II) bromide complexes in the xCa(NO₃)₂–(1 − x)NH₄NO₃–H₂O system. Measurements were conducted within the wavelength range of 400–800 nm, at a constant temperature of T = 328.15 K and atmospheric pressure of p = 101.3 kPa. The spectra were recorded for systems with a fixed salt composition of 0.3Ca(NO₃)₂–0.7NH₄NO₃–H₂O, but with varying water content, described by the mole ratio of water to salt (R = H₂O/salt), where R was set to 1.0, 1.2, and 1.6. Additionally, the study investigated systems with varying calcium nitrate-to-ammonium nitrate ratios, represented as xCa(NO₃)₂–(1 − x)NH₄NO₃–H₂O, where x takes the values 0.3, 0.4, and 0.6. In these systems, the mole ratio of water to total salt was kept constant at R = 1.6. For systems with x = 0.7 and 0.9, a higher water-to-salt mole ratio of R = 3.6 was used. The analysis of absorption spectra revealed a shift of the maximum absorption peak toward shorter wavelengths (blue shift) as the water content (R) increased. This behavior suggests that both water molecules and nitrate ions participate in the coordination around the cobalt(II) ion. Based on the spectral data, the presence of the following complexes was confirmed: [Co(NO₃)₄(H₂O)₂]²⁻, [Co(NO₃)₂Br₂]²⁻ and [CoBr₄]²⁻. The overall stability constants of these complexes were calculated, and the corresponding resolved spectra of the species were determined at T = 328.15 K.