Thermodynamics Of Dissolution Research Articles

Thermodynamics of dissolution of chromium(III) and cobalt(III) trisacetylacetonates in water-ethanol solvents

The study presents solubility data for chromium(III) and cobalt(III) trisacetylacetonates in water-ethanol solvents over a wide range of temperatures and ethanol concentrations. The solubilities of both compounds increase as the temperature or ethanol concentration is raised, particularly in the case of Cr(acac)3 it increases to a greater extent. Noteworthy, for ethanol concentrations of 1.4–1.6 mol/L tinversion of the temperature effect on the solubilities of both compounds is observed. For ethanol concentrations lower than 1.4–1.6 mol/L, dissolution of Cr(acac)3 and Co(acac)3 is exothermic, whereas for the higher concentrations, it is endothermic. The changes in enthalpy and entropy upon dissolution of the compounds under study were evaluated using the temperature dependence of solubility.

Equilibrium parameters of a liquid—vapor system and thermodynamic characteristics of adsorption of cyclic and cage hydrocarbons in squalane

The thermodynamic characteristics of adsorption of adamantane molecules and its alkyl derivatives, as well as some mono- and bicyclic hydrocarbons C10H n , were studied by equilibrium gas liquid chromatography on a column packed with the stationary liquid phase squalane under the conditions of infinitely low concentrations of the sorbate in the gas phase. The influence of specific features of the molecular structure of sorbates on the regularities of their retention on the column with squalane was shown. For the first time we obtained the limiting activity coefficients and excess thermodynamic functions of mixing, which made it possible to study in detail the thermodynamics of dissolution of cage molecules in the nonpolar liquid bulk. The changes in the molar isobaric heat capacity of sorbates during adsorption were determined by the chromatographic method. For reference compounds, these values agree well with the results of direct calorimetric measurements of the change in the molar standard isobaric heat capacity during vaporization.

Thermodynamics of Dissolution for Bis(triazine)−Bipyridine-Class Ligands in Different Diluents and Its Reflection on Extraction

Hydrochemical separation processes are one of the methods used for the treatment of spent nuclear fuel. Solvent extraction is also used in many other non-nuclear applications like the mining industry. In the nuclear case, hydrochemical separation processes are already employed in the world today for the recovery of uranium and plutonium. The method is however also considered for future separation systems for use in combination with the transmutation of the minor actinides. In a hydrochemical separation process the two phases are the pregnant (usually) aqueous feed and the organic phase comprising a diluent together with one or more extractants. One such class of extractants developed for partitioning and transmutation purposes is the bis(triazine)−bipyridine-type (BTBP) molecules. When assessing the feasibility and loading properties of such an extraction system, the solubility of the ligands is of the outmost importance. The understanding of whether the dissolution is enthalpically or entropically driven will also help the understanding of the differences in extraction observed between various diluents and temperatures. In this paper the enthalpy and entropy of dissolution of the BTBP-class ligands have been determined for different diluents. It has also been shown that it is possible to predict the extraction behavior of these molecules in the selected diluent once the solubility is known.

Thermodynamics of solvation of calix[4]arenes in n-hexane

The solubility of eight calix[4]arenes and crown-calix[4]arenes in n-hexane at five different temperatures was determined by isothermal saturation. The thermodynamic dissolution parameters were calculated. Thermodynamics of solvation in n-hexane was calculated using thermodynamic parameters of sublimation obtained earlier. Thermogravimetric analysis of the bottom phase was carried out to detect crystallosolvates. The stoichiometry of the crystallosolvates formed was ascertained.

Thermodynamics of moisture dissolution in diesel fuel

The thermodynamic aspects of the dissolution of water (moisture) in diesel fuels have been considered. For theoretical analysis, the basic features of moisture dissolution in individual liquid hydrocarbons and diesel fuel at different temperatures have been considered. The parametric equations proposed in this work made it possible to determine the heats and entropies of a solution of water in individual liquid hydrocarbons and diesel fuel. The values obtained for diesel fuel were about 40 kJ/mol and 92.08 J/(mol K), respectively, which correspond to the chemical composition of the test diesel sample. On the basis of the results of the study, a mechanism has been put forth for the interaction of water molecules with the molecules of individual hydrocarbons and diesel fuel.

Clinopyroxene dissolution in basaltic melt

The history of magmatic systems may be inferred from reactions between mantle xenoliths and host basalt if the thermodynamics and kinetics of the reactions are quantified. To study diffusive and convective clinopyroxene dissolution in silicate melts, diffusive clinopyroxene dissolution experiments were conducted at 0.47–1.90 GPa and 1509–1790 K in a piston-cylinder apparatus. Clinopyroxene saturation is found to be roughly determined by MgO and CaO content. The effective binary diffusivities, D MgO and D CaO, and the interface melt saturation condition, C 0 MgO × C 0 CaO , are extracted from the experiments. D MgO and D CaO show Arrhenian dependence on temperature. The pressure dependence is small and not resolved within 0.47–1.90 GPa. C 0 MgO × C 0 CaO in the interface melt increases with increasing temperature, but decreases with increasing pressure. Convective clinopyroxene dissolution, where the convection is driven by the density difference between the crystal and melt, is modeled using the diffusivities and interface melt saturation condition. Previous studies showed that the convective dissolution rate depends on the thermodynamics, kinetics and fluid dynamics of the system. Comparing our results for clinopyroxene dissolution to results from a previous study on convective olivine dissolution shows that the kinetic and fluid dynamic aspects of the two minerals are quite similar. However, the thermodynamics of clinopyroxene dissolution depends more strongly on the degree of superheating and composition of the host melt than that of olivine dissolution. The models for clinopyroxene and olivine dissolution are tested against literature experiments on mineral–melt interaction. They are then applied to previously proposed reactions between Hawaii basalts and mantle minerals, mid-ocean ridge basalts and mantle minerals, and xenoliths digestion in a basalt at Kuandian, Northeast China.

Thermodynamics of Copper Dissolution into MnO–SiO2–MnS Inclusion System

Recently, a new process has been introduced to control α-γ transformation of steels using cuprous sulfide precipitates on the MnO bearing oxide inclusion as well as MnS. In order to optimize the composition of inclusions, the solubility of copper into MnO-SiO 2 -MnS system were measured at 1 523 K and a dissolution mechanism of copper into an oxy-sulfide melts and cuprous sulfide capacity has been proposed. The solubility of copper increased with an increase in MnO/(MnO+SiO 2 ) ratio and showed a maximum solubility at MnO and MnS doubly saturated composition, which was consistent with the maximum precipitation ratio of CuS. Deliberating an oxy-sulfide melts saturated with MnS, MnO, and SiO 2 at 1 523 K, the phase diagram for the MnO-SiO 2 -MnS system indicated that the activity coefficient of cuprous sulfide in an oxy-sulfide melts was dependent on the activity of MnO and the activity coefficient of MnS. The dissolution mechanism of copper into a MnO-MnS inclusion system was confirmed and cuprous sulfide capacity was also defined from the reaction mechanism. Cuprous sulfide capacity for the MnO-MnS bearing inclusion strongly depends on stability of sulfide and basicity. The experimental results revealed that the optimized composition for inclusion to dissolve copper was (mass%MnO)=43.6, (mass%SiO 2 )=1.8 and (mass%MnS)=54.6. Consequently, it could be proposed that the harmlessness of copper in scrap and dispersion strengthening could be possible by using the non-metallic inclusion technique.

Water-DMF-L-α-alanine and water-carbamide-L-α-alanine systems. Thermodynamic properties, solvation, and interspecies interactions at 273–333 K

Thermal effects of dissolution of L-α-alanine in water-N,N-dimethylformamide mixtures (0–0.1 molar parts of DMF) at 283–318 K were measured calorimetrically. Standard enthalpies and heat capacities of dissolution of the amino acid and also thermal variations in entropies and free energies were calculated. The comparison with previously obtained data on the thermodynamics of dissolution of L-α-alamine in the carbamide water solution was performed. Temperature variations in the reduced Gibbs energy in the course of dissolution of L-α-alanine in water-DMF and water-carbamide mixtures have negative values originating from the prevalence of the entropy component. At the increase in temperature both mixtures become less structured. The interaction of L-α-alanine with hydrophilic and hydrophobic amides differs fundamentally: In the first case it is enthalpy-attractive and does not depend on temperature, while in the second case it is repulsive and decreases with the increase in temperature.

Thermodynamics of Non-Reactive Gases Dissolved in Water at Ambient Temperature (T≤333 K): an Update

The thermodynamics of dissolution of non-reactive gases in water under ambient conditions is of importance for the description of the properties of small hydrophobic solutes, and they are also of interest for environmental assessments. The review published in 1977 by Wilhelm, Battino and Wilcock (Chem. Rev. 77:219–262, 1977) constitutes a milestone in this field. However, a number of new data have been published since then, including both solubility and calorimetric determinations. We have analyzed the new data for 27 binary systems reported in the literature at the time of writing this article. Whenever solubility and calorimetric data both exist they have been fitted together. There are, however, systems for which only one type of new thermodynamic information is available; these systems were also analyzed using procedures that are described in this work.

Thermodynamics of ferrocene dissolution in water-methanol solutions

The polythermal solubility of ferrocene in water-methanol solutions in a wide range of their compositions was studied. Ferrocene solubility grows as temperature and methanol content increase. Thermodynamic functions of ferrocene transfer from water into water-methanol solutions were calculated. The results obtained were compared with the data on neon solubility in the same solvent.

Adhesives as polymer blends

Specific features of the phase equilibrium in adhesive compositions based on polymer blends are considered. It is shown that polymer blends can be characterized by structures of three types: a single-phase system in the case of complete mutual solubility, the dispersion of one polymer in a continuous matrix of another polymer, and a two-phase continuous system (interpenetrating networks). Some problems of the kinetics and thermodynamics of polymer dissolution in a polymeric medium are considered for each of the aforementioned three types of structures. It is established that the final structure of a polymer blend after the evaporation of solvent is determined by the kinetic potentialities for the attainment of thermodynamic equilibrium of the phase state. The dependence of the structure on the solution viscosity is studied by the example of high-molecular-weight butadiene-acrylonitrile rubber and epoxy resin in a mixture of acetone and toluene. Regularities of the formation of the phase structure of an adhesive that make it possible to guarantee the stability of article properties are revealed.

Amino acids in aqueous solution. Effect of molecular structure and temperature on thermodynamics of dissolution

The enthalpies of dissolution of glycine (Gly) and L-α-alanine (Ala) in water at 288.15–318.15 K were measured. The results were compared with the earlier obtained data for L-α-phenylalanine (Phe) and L-α-histidine (His). The standard enthalpies of dissolution (Δsoln H 0) and differences (ΔC p 0 ) between the limiting partial molar heat capacity of the amino acids in solution and the heat capacity of the amino acids in the crystalline state \((\Delta C_p ^0 = \bar C_{p,2}^\infty - C_p )\) were calculated in the temperature interval 273–373 K. Changes in the entropy of dissolution (ΔΔsoln S 0) and reduced Gibbs energy [Δ (Δsoln G 0/T)] in the temperature interval from 273 to 373 K were determined from the known thermodynamic relationships. The ΔC p 0 value is negative for hydrophilic glycine and positive for other amino acids. The ΔΔsoln S 0 values increase with an increase in the hydrophobicity of the amino acids. The Δ(Δsoln G 0/T) values become more negative in the order Ala, Phe, Gly, His.

Coal Chemistry for Mechanical Engineers: From Macromolecular Thermodynamics to Reservoir Simulation

In pilot trials and commercial scale field demonstrations of CO2 storage in coal seams, quite often unexpected problems with coal swelling around injector and reducing injection efficiency (e.g., Allison unit in the San Juan Basin, RECOPOL in Poland, Hokkaido project in Japan, etc.) can stall or even terminate the site development. To avoid the costly mistakes with the prospective site evaluation, the state of the art in reservoir modeling needs to be improved by taking into account coal properties at the macromolecular level. The current models are based on the rock mechanics, which ignores decades of experimental and theoretical studies of interaction between coal and injected fluids. A pseudopolymer approach is introduced to the modelers as a viable alternative, especially, at medium to high fluid pressures. Further, it is discussed how the thermodynamics of CO2 dissolution in the macromolecular network of the coal matrix can be incorporated into geomechanical models.

Electrochemical dissolution of surface alloys in acids: Thermodynamic trends from first-principles calculations

A simple procedure is introduced to use periodic Density Functional Theory calculations to estimate trends in the thermodynamics of surface alloy dissolution in acidic media. With this approach, the dissolution potentials for solute metal atoms embedded in the surface layer of various host metals (referenced to the dissolution potential of the solute in its pure, metallic form) are calculated. Periodic trends in the calculated potentials are found to be related to trends in surface segregation energies of the various solute/host pairs. The effects of water splitting and concomitant hydroxyl adsorption on the dissolution potentials are also considered; these effects do not change the potentials for highly oxophilic solutes embedded in less active hosts, but they do decrease the dissolution potential for more inert solutes on oxophilic hosts. Finally, the dissolution of Pt “skin” layers from Pt 3X (X = Fe, Co, and Ni) bulk alloys is analyzed; the Pt skins are found to be stabilized compared to pure Pt.

Kinetics and thermodynamics of aluminium dissolution in 1.0 M sulphuric acid containing chloride ions

The dissolution of aluminium in 1 M sulphuric acid solutions containing different chloride ion concentrations (0.01–0.06 M) were studied at 25, 30, 35 and 40 °C using electrochemical impedance spectroscopy (EIS) technique and polarization curves measurements. The kinetic rate equation, under the experimental condition described, was derived and found to verify the following relationship: V = k obs K 2 C C l − n 1 + K 2 C C l − n where V is the corrosion rate, k obs and K 2 are the dissolution rate constant of aluminium oxide–chloride complex and the equilibrium constant of chloride ions adsorbed at aluminium oxide surface, respectively. The kinetic and thermodynamic energy parameters were calculated and their values indicate that chloride ions are chemisorbed onto the aluminium oxide surface and the formation of oxide–chloride complex is the rate-determining step.

Electronic structures of iron(III) and manganese(IV) (hydr)oxide minerals: Thermodynamics of photochemical reductive dissolution in aquatic environments

Sunlight-induced reduction and dissolution of colloidal Fe-Mn (hydr)oxide minerals yields elevated concentrations of Fe 2+ and Mn 2+ in natural waters. Since these elements may be biolimiting micronutrients, photochemical reactions might play a significant role in biogeochemical cycles. Reductive photodissolution of Fe (hydr)oxide minerals may also release sorbed metals. The reactivity of Fe-Mn (hydr)oxide minerals to sunlight-induced photochemical dissolution is determined by the electronic structure of the mineral-water interface. In this work, oxygen K-edge absorption and emission spectra were used to determine the electronic structures of iron(III) (hydr)oxides (hematite, goethite, lepidocrocite, akaganeite and schwertmannite) and manganese(IV) oxides (pyrolusite, birnessite, cryptomelane). The band gaps in the iron(III) (hydr)oxide minerals are near 2.0–2.5 eV; the band gaps in the manganese (IV) oxide phases are 1.0–1.8 eV. Using published values for the electrochemical flat-band potential for hematite together with experimental pH pzc values for the (hydr)oxides, it is possible to predict the electrochemical potentials of the conduction and valence bands in aqueous solutions as a function of pH. The band potentials enable semiquantitative predictions of the susceptibilities of these minerals to photochemical dissolution in aqueous solutions. At pH 2 (e.g., acid-mine waters), photoreduction of iron(III) (hydr)oxides could yield millimolal concentrations of aqueous Fe 2+ (assuming surface detachment of Fe 2+ is not rate limiting). In seawater (pH 8.3), however, the direct photo-reduction of colloidal iron(III) (hydr)oxides to give nanomolal concentrations of dissolved, uncomplexed, Fe 2+ is not thermodynamically feasible. This supports the hypothesis that the apparent photodissolution of iron(III) (hydr)oxides in marines systems results from Fe 3+ reduction by photochemically produced superoxide. In contrast, the direct photoreduction of manganese oxides should be energetically feasible at pH 2 and 8.3.

Voltammetric Studies on Decaphenylferrocene, Substituted Decaphenylferrocenes, and Their Oxidized Forms in Dichloromethane and Ionic Liquids

Cyclic voltammetric studies have been undertaken on highly insoluble decaphenylferrocene (DPFc), on substituted forms of the compound [methyl (Me 2 DPFc, Me 6 DPFc, and Me 1 0 DPFc), bromide (Br 2 DPFc), and ethynyl (Ethin 2 DPFc)], and on their more soluble one-electron-oxidized DPFc + forms. Studies with DPFc + and its derivatives dissolved in dichloromethane (DCM) enable the reversible potentials (E 0 ') of one-electron reduction processes, DPFc + (DCM) + e - ⇄ DPFc(DCM), to be established. E 0 ' values obtained from these measurements exhibit the expected substituent dependence. Voltammetric studies with arrays of insoluble DPFc microparticles adhered to an electrode surface in contact with DCM (0.1 M Bu 4 NPF 6 ) or ionic liquids are connected to the oxidized solid or dissolved forms of DPFc + via a range of pathways that are determined by the kinetics and thermodynamics of dissolution and reprecipitation processes. Comparative data obtained with more soluble ferrocene, ferri-cinium, and decamethylferrocene microparticles support the hypothesis that dissolution processes play an important role in determining the nature of the voltammetric response of adhered microparticles.

CHEMICAL DISSOLUTION OF NICKEL (II) OXIDE AND HYDROXIDE IN AMINO ACID SOLUTIONS

Simulation experimenting has been used to analyze thermodynamics of chemical dissolution of nickel (II) oxide and hydroxide in solutions containing various amino acids. Allowance for complexation, protonation and hydrolysis processes has been found to be a must for adequate description of chemical processes.

Extraction of Organic Oil from Sea Buckthorn Seeds with Supercritical Carbon Dioxide

The extraction of fatty acids and their derivatives from sea buckthorn seeds with supercritical carbon dioxide is experimentally studied. A theoretical model of supercritical extraction of organic oil is constructed. The thermodynamics of dissolution of high-molecular-weight substances under supercritical conditions is described in terms of the Redlich–Kwong equation of state. The diffusion of macromolecules of substances contained in organic oil in seed pores is described using a model of a contracting core. The calculated results are compared to experimental data. The pseudocritical parameters of organic oil and its saturation vapor pressure are estimated.

Thermodynamics and Kinetics of the Dissolution of Gold Under Pressure Oxidation Conditions in the Presence of Chloride

Thermodynamics and Kinetics of the Dissolution of Gold Under Pressure Oxidation Conditions in the Presence of Chloride