Solid Equilibrium Research Articles

The kinetics of CO2 indirect mineralization of [formula omitted] to produce [formula omitted

The CO2 mineralization is an economical route to reduce CO2 emission for the production of high-value carbonate products. The performance of CO2 indirect mineralization of MgSO4 by (NH4)2CO3 solution was studied systematically. The effects of process parameters on the reaction performance and morphology of MgCO3·3H2O were investigated. In the reaction process, three stages were observed, including nucleation induction, solid phase growth and equilibrium stage. The nucleation induction period and equilibrium time are shortened with the increase of reaction temperature, initial reactants concentration, stirring speed and (NH4)2CO3/MgSO4 molar ratio. These parameters also play a vital role in the morphology of products. It was found that the difference between crystal growth rate and mass transfer rate has a significant impact on crystal morphology. A kinetic model was derived from the solid phase growth rate. The estimated activation energies of forward and reverse reaction are 30.37 kJ/mol and 32.71 kJ/mol, respectively.

Phase Behavior in Aqueous Two-Phase Systems Based-Ionic Liquid Composed of 1-Butyl-3-methylimidazolium Tetrafluoroborate and Copper Sulfate in Different Temperatures

Phase behavior of new aqueous two-phase systems (ATPSs) composed by 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) + copper sulfate (CuSO4) + water systems were determined experimentally at T = (283.15, 298.15, and 313.15) K. The phase diagrams obtained at the different study temperatures describe the liquid–liquid equilibrium (LLE) and, in some cases, the liquid–liquid–solid equilibrium for different mixture compositions. The effects of the temperature, composition, and ion exchange in the formation of this ATPS were available. The temperature had a remarkable effect on the position of phase diagrams. The decrease in temperature promoted phase separation indicating the exothermic character of formation of these ATPSs, and further, at temperatures of 283.15 and 298.15 K it was observed that there was phase inversion for some mixture compositions that occurred. The extent of the ionic exchange of the original ionic pairs between the phases in equilibrium was evaluated considering the electroneut...

Desalination by cooling and freezing of seawater and groundwater: thermodynamic aspect of the liquid–solid equilibrium

Desalination by cooling and freezing of seawater and groundwater: thermodynamic aspect of the liquid–solid equilibrium

Patagonian salt marsh soils and oxidizable pedogenic pyrite: solid phases controlling aluminum and iron contents in acidic soil solutions

The sulfidic materials present in salt marshes could be oxidized forming sulfuric acid, increasing the toxic levels of both Al and Fe available to plants. The objectives of this study were: (a) to evaluate the mechanism of acid generation from the oxidation of sulfidic materials, and (b) to predict solid phases governing the dissolved Fe and Al concentrations in soils at low pH. The study was conducted in 14 soil profiles associated to eight salt marshes situated along the Atlantic coast of Patagonia. The potential acidity was estimated by the peroxide-oxidizable sulfuric acidity method (POSA). To predict the availability of Fe and Al at low pH, the solid phase equilibrium that governs the solubility of these elements through ion activity of the products was determined. The scanning electron microscopy analysis in sulfidic materials reveals the occurrence of framboidal pyrite. The relative variability of POSA at low pH values may indicate retention of sulfates by Al and Fe hydroxides, producing the formation of basic sulfates of iron and aluminum. At pH > 5.5, Fe2+ and Al3+ activities show an equilibrium with amorphous oxy-hydroxides of Fe(OH)3 and gibbsite, respectively. As the pH begins to decline below 5.5, Fe2+ and Al3+ activities show an equilibrium with respect to soil–Fe(OH)3 and Al(OH)3 amorphous, respectively. While for more acidic conditions, the solid phase in predicting both Fe2+ and Al3+ activities was basic iron sulfate and jurbanite. The acidic soil solutions with pH < 3, Fe2+ and SO42− activities show an equilibrium with goethite and melanterite, respectively. As a consequence of acid generation, phosphorus adsorption by aluminum and iron oxide minerals was detected.

Thermodynamic phases in two-dimensional active matter

Active matter has been much studied for its intriguing properties such as collective motion, motility-induced phase separation and giant fluctuations. However, it has remained unclear how the states of active materials connect with the equilibrium phases. For two-dimensional systems, this is also because the understanding of the liquid, hexatic, and solid equilibrium phases and their phase transitions is recent. Here we show that two-dimensional self-propelled point particles with inverse-power-law repulsions moving with a kinetic Monte Carlo algorithm without alignment interactions preserve all equilibrium phases up to very large activities. Furthermore, at high activity within the liquid phase, a critical point opens up a gas–liquid motility-induced phase separation region. In our model, two-step melting and motility-induced phase separation are thus independent phenomena. We discuss the reasons for these findings to be common to a wide class of two-dimensional active systems.

Thermodynamic modeling of the system of CO2 and potassium taurate solution for simulation of the carbon dioxide capture process

Absorption of carbon dioxide from gaseous sources such as flue gases from power plants is accomplished for environmental reasons with the aim to reduce emissions of greenhouse gases. Generally, aqueous solutions of alkanolamines are employed with Monoethanolamine (MEA) considered the benchmark solvent. However, it has drawbacks, primarily its volatility and toxicity, and the need for a lot of energy for regeneration. Recently, new solvents such as amino acid aqueous solutions have started to be considered as alternatives to traditional amines.This paper is focused on the development of a model for the simulation of the absorption and regeneration system using potassium taurate for the capture of carbon dioxide. Detailed modelling of this system is currently limited by the lack of thermodynamic parameters for use in simulations. ASPEN Plus® has been chosen as the framework for developing the model. Species not present by default in the database have been added and appropriate parameters have been determined for obtaining a reliable description of the Vapor–Liquid–Solid Equilibrium by means of the Electrolyte-NRTL method.

Solid State Phase Equilibria and Solid Solution of the Si-Y-Zr Ternary System at 1173 K

Insight into the phase equilibria, intermetallic compounds, solid solution and thermodynamic properties of the system of Zr, Si and rare earth elements is of academic interest for development of key structural materials in many fields. In this work, the solid state phase equilibria of the Si-Y-Zr ternary system at 1173 K were experimentally investigated by using x-ray powder diffraction and backscattered electron with energy dispersive x-ray analysis. The existence of 10 binary compounds namely, SiZr2, α-Si4Zr5, Si2Zr3, Si2Zr, α-SiZr, α-Si2Y, β-Si5Y3, SiY, Si4Y5 and Si3Y5, have been confirmed in this system at 1173 K, respectively. No binary compound was found in the Y-Zr binary system, and no ternary compound was found in current ternary system. The solid solubility of Y in the phases SiZr2, α-Si4Zr5, Si2Zr3, Si2Zr, α-SiZr, and Zr in α-Si2Y, β-Si5Y3, SiY, Si4Y5 and Si3Y5 was determined at 1173 K.

Recovery and Recycling of Isopropyl Alcohol Used in Biodiesel Production From Yellow Mustard Oil

AbstractThe recovery of solvents used during biodiesel synthesis is an important factor in the economic feasibility and sustainability of the entire process. In this study, we looked at the use of isopropyl alcohol (IPA) for oil extraction and biodiesel production, as well as its potential for recovery and recycling. We found that multistage extraction improved oil recovery, with up to 86% oil yield using four stages of extraction at an IPA:mustard flour (volume:weight) ratio of 1.5:1 at room temperature. Using acid–base‐catalyzed transesterification, 99% of the mustard oil was converted to biodiesel. At the end of this process, IPA was recovered from the azeotrope by salting out using potassium carbonate or sodium carbonate. The solubility behavior of the components was evaluated by means of ternary‐phase diagrams of IPA/water/sodium carbonate and IPA/water/potassium carbonate, which determined their liquid–liquid–solid equilibrium constants at ambient pressure and at room temperature. Using 20% (w:w) potassium carbonate, 95% of the IPA was recovered at 99% purity from a starting mixture of IPA containing 13% water. Azeotropic distillation of the IPA–water azeotrope with 10% potassium carbonate resulted in the recovery of 99% of the IPA at 94% purity. These results suggest that IPA is not only a suitable solvent for mustard‐oil extraction but also for salt‐enhanced azeotropic distillation resulting in near‐complete recovery from aqueous solutions.

Is the Li–S battery an everlasting challenge for operando techniques?

The promise of high-energy density and the predicted role of the Li–S batteries in electrochemical energy storage applications are largely based on sulfur's high theoretical specific charge. Unfortunately, to date the commercialization of Li–S battery is still hindered due to the complexity of the reaction mechanism involving a sequence of dynamically changing liquid and solid equilibria. Operando techniques have been widely employed to study these performance-limiting phase transformations; however, they often fall short in tracking and resolving simultaneously the solid and liquid phases. Here, we present a review summarizing the last efforts in the field.

Modelling of auto-agglomeration of cohesive powders

Fine particles in the micron size range or smaller are usually so cohesive that they cannot exist as individual entities and are in cluster form, the size of which depends on the stress history. During handling, transportation or storage, the powder is subjected to mechanical vibration and/or agitation and, as a result of which clumping of particles or “snowballing” can occur even without the presence of any binder. This is an undesirable feature, as it is responsible for poor flow behaviour, cohesive arching, segregation of lumps and inducing flaws in products. Nevertheless, the mechanism of auto-agglomeration of cohesive powder has not received due attention and the conditions under which such clusters/lumps form, their size, structure and strength has not been analysed extensively. In this work we present a preliminary model to predict the equilibrium cluster size based on two separate energy balances to predict the granule solid fraction and equilibrium size, respectively. Despite some broad approximations, this approach can capture the trend of variation of the agglomerate size with the vibration intensity for some data reported in the literature. The proposed model also identifies the mechanism controlling the growth of the agglomerates as the balance between the cohesive energy of the particles and the disruptive energy of vibration.

The mechanical equilibrium of soft solids with surface elasticity.

Recent experiments have shown that surface stresses in soft materials can have a significant strain-dependence. Here we explore the implications of this surface elasticity to show how, and when, we expect it to arise. We develop the appropriate boundary condition, showing that it simplifies significantly in certain cases. We show that surface elasticity's main role is to stiffen a solid surface's response to in-plane tractions, in particular at length-scales smaller than a characteristic elastocapillary length. We also investigate how surface elasticity affects the Green's-function problem of a line force on a flat, incompressible, linear-elastic substrate. There are significant changes to this solution, especially in that the well-known displacement singularity is regularised. This raises interesting implications for soft phenomena like wetting contact lines, adhesion and friction. Finally, we discuss open questions, future directions, and close ties with existing fields of research.

Solid Phase Equilibrium Relations in the CaO-SiO2-Nb2O5-La2O3 System at 1273 K

Silicate slag system with additions Nb and RE formed in the utilization of REE-Nb-Fe ore deposit resources in China has industrial uses as a metallurgical slag system. The lack of a phase diagram, theoretical, and thermodynamic information for the multi-component system restrict the comprehensive utilization process. In the current work, solid phase equilibrium relations in the CaO-SiO2-Nb2O5-La2O3 quaternary system at 1273 K (1000 °C) were investigated experimentally by the high-temperature equilibrium experiment followed by X-ray diffraction, scanning electron microscope, and energy dispersive spectrometer. Six spatial independent tetrahedron fields in the CaO-SiO2-Nb2O5-La2O3 system phase diagram were determined by the Gibbs Phase Rule. The current work combines the mass fraction of equilibrium phase and corresponding geometric relation. A determinant method was deduced to calculate the mass fraction of equilibrium phase in quaternary system according to the Mass Conservation Law, the Gibbs Phase Rule, the Lever’s Rule, and the Cramer Law.

Comparison of the Melting Temperatures of Classical and Quantum Water Potential Models

As theoretical approaches and technical methods improve over time, the field of computer simulations for water has greatly progressed. Water potential models become much more complex when additional interactions and advanced theories are considered. Macroscopic properties of water predicted by computer simulations using water potential models are expected to be consistent with experimental outcomes. As such, discrepancies between computer simulations and experiments could be a criterion to comment on the performances of various water potential models. Notably, water can occur not only as liquid phases but also as solid and vapor phases. Therefore, the melting temperature related to the solid and liquid phase equilibrium is an effective parameter to judge the performances of different water potential models. As a mini review, our purpose is to introduce some water models developed in recent years and the melting temperatures obtained through simulations with such models. Moreover, some explanations referred to in the literature are described for the additional evaluation of the water potential models.

Variable potentials for thermalized light and coupled condensates

For over a decade, cold atoms in lattice potentials have been an attractive platform to simulate phenomena known from solid state theory, as the Mott-insulator transition. In contrast, the field of photonics usually deals with non-equilibrium physics. Recent advances towards photonic simulators of solid state equilibrium effects include polariton double-site and lattice experiments, as well as the demonstration of a photon condensate in a dye-filled microcavity. Here we demonstrate a technique to create variable micropotentials for light using thermo-optic imprinting within an ultrahigh-reflectivity mirror microcavity filled with a dye-polymer solution that is compatible with photon gas thermalization. By repeated absorption-emission cycles photons thermalize to the temperature of the dye solution, and in a single microsite we observe a photon Bose-Einstein microcondensate. Effective interactions between the otherwise nearly non-interacting photons are observed due to thermo-optic effects, and in a double-well system tunnel coupling between sites is demonstrated, as well as the hybridization of eigenstates. Prospects of the new experimental platform include photonic structures in which photons thermalize into entangled manybody states.

Cr(VI) removal from aqueous solutions using aluminosilicate minerals in their Pb-exchanged forms

This work investigated the removal of Cr(VI) from aqueous solutions by employing Pb-modified zeolite, vermiculite and perlite as adsorbents. Natural zeolite and vermiculite exhibited high Pb2+ adsorption (~80% of the total Pb2+ concentration in solution), while perlite resulted in low lead adsorption (21%). Subsequently, the Pb-modified zeolite and vermiculite exhibited high Cr(VI) adsorption. The maximum Cr(VI) adsorption capacity as predicted by the Langmuir isotherm was 18.9mgg−1 for zeolite and 23.0mgg−1 for vermiculite. Langmuir was the isotherm equation that best fitted the experimental data. In terms of kinetics the Elovich equation represented the best fit to Cr(VI) adsorption on the studied modified minerals. The lowest mineral concentration that was tested (10gL−1) resulted in the highest solid phase equilibrium concentration. Desorption experiments were not effective since the desorption percent achieved with NaCl solution was very low (4–6%). Cr(VI) removal using Pb-modified minerals can be applied in the successive treatment of industrial wastewater first for lead and then for Cr(VI) removal.

Replica exchange molecular simulation of Lennard–Jones particles in a two-dimensional confined system

Confined systems exhibit interesting properties that are applied to the fields of lubrication, adhesion and nanotechnology. The replica exchange molecular simulation method was applied to calculate the phase equilibrium points of Lennard–Jones particles in a two-dimensional confined system. The liquid–solid phase equilibrium points and the solid structure with a dependency of the slit width were determined and the order parameter of the solid structure was analyzed. Such confined systems are shown to be favorable for manipulation of the phase equilibrium points.

The role of particle size of glyburide crystals in improving its oral absorption.

Currently, nanosizing is becoming increasingly prevalent as an efficient way for the improvement of oral drug absorption. This study mainly focuses on two points, namely the crystal properties, and the in vitro and in vivo characterizations of drug crystals during the nanosizing process. We used glyburide, an oral type 2 diabetes (T2D) medication, as our model drug. We sought to reduce the crystalline size of this drug and evaluate its absorption properties by comparing it with the original coarse drug because of previous reports about its gastrointestinal absorption insufficiency. Glyburide crystals, ranging from 237.6 to 4473nm were prepared successfully by jet milling and media milling. The particle sizes and the crystal morphology were analyzed by characterization of the solid states, equilibrium solubility, and dissolution behavior. Additionally, pharmacokinetic study was performed in SD rats. The solid state results indicated a loss in crystallinity, amide-imidic acid interconversion, and partial amorphization during nanosizing. Further, in in vitro tests, nanocrystal formulations remarkably increased the solubility and dissolution of the drug (compared to microcrystals). In the in vivo test, reducing the particle size from 601.3 to 312.5nm showed no improvement on the C max and AUC (0-36h) values, while a profound slowing of the drug elimination occurred with reduction of particle size. Further reduction from 312.5 to 237.6nm lead to a significant increase (p<0.001) of the AUC (0-36h) from 6857.8±369.3ngmL-1h to 12,928.3±1591.4ngmL-1h, respectively, in rats. Our present study confirmed that nanosizing has a tremendous impact on promoting the oral absorption of glyburide.

On the Lennard-Jones and Devonshire theory for solid state thermodynamics

ABSTRACTThe Lennard-Jones and Devonshire theory is developed into a self-consistent scheme for essentially complete thermodynamic information. The resulting methodology is compared with molecular simulation of the Lennard-Jones system in the face-centred-cubic solid state over an excessive range of state points. The thermal and caloric equations of state are in almost perfect agreement along the entire fluid–solid coexistence lines over more than six orders of magnitude in pressure. For homogeneous densities greater than twice the solid triple point density, the theory is essentially exact for derivatives of the Helmholtz energy. However, the fluid–solid phase equilibria are in disagreement with simulation. It is shown that the theory is in error by an additive constant to the Helmholtz energy A/(NkBT). Empirical inclusion of the error term makes all fluid–solid equilibria indistinguishable from exact results. Some arguments about the origin of the error are given.

Phenomenological study on heat and mass coupling mechanism of waxy crude oil pipeline transport process

ABSTRACTBased on the phase equilibrium model of the paraffin wax precipitation in the process of oil pipeline transportation, theory and method of non-equilibrium thermodynamics were applied to obtain the linear phenomenological equations for the cross-interaction of heat and mass transfer during pipeline transport, which were derived from the irreversible entropy production rate equation. Then, the analysis of the irreversible heat flow and the mass flow were carried out, and the mathematical expressions of the phenomenological coefficient of liquid phase, the phenomenological coefficient of solid phase flow, and the heat flow phenomenological coefficient were obtained. Taking a waxy crude oil transportation pipeline in Daqing Oilfield as an example, based on the analysis of liquid–solid phase equilibrium, the irreversible linear phenomenological mechanism of heat and mass coupling in waxy crude oil pipeline transportation was analyzed in detail from three levels: phenomenological coefficients which reflect characteristic of the effect of force on flow in heat and mass transfer; thermodynamic forces which trigger heat and mass transfer; transmitted heat and mass flow density, providing a theoretical basis for the further study of the wax deposition in the process of pipeline transportation.

A comparison of Redlich-Kister polynomial and cubic spline representations of the chemical potential in phase field computations

Free energies play a central role in many descriptions of equilibrium and non-equilibrium properties of solids. Continuum partial differential equations (PDEs) of atomic transport, phase transformations and mechanics often rely on first and second derivatives of a free energy function. The stability, accuracy and robustness of numerical methods to solve these PDEs are sensitive to the particular functional representations of the free energy. In this communication we investigate the influence of different representations of thermodynamic data on phase field computations of diffusion and two-phase reactions in the solid state. First-principles statistical mechanics methods were used to generate realistic free energy data for HCP titanium with interstitially dissolved oxygen. While Redlich-Kister polynomials have formed the mainstay of thermodynamic descriptions of multi-component solids, they require high order terms to fit oscillations in chemical potentials around phase transitions. Here, we demonstrate that high fidelity fits to rapidly fluctuating free energy functions are obtained with spline functions. Spline functions that are many degrees lower than Redlich-Kister polynomials provide equal or superior fits to chemical potential data and, when used in phase field computations, result in solution times approaching an order of magnitude speed up relative to the use of Redlich-Kister polynomials.