Set Of Thermodynamic Data Research Articles

Dielectric properties of organofunctionalized kaolinite clay and application in adsorption mercury cation

Kaolinite clay samples from Amazon region, Pará state, Brazil, were first intercalated with dimethylsulfoxide (DS) followed by immobilization of (3-aminopropyl)triethoxysilane (APS). The samples were characterized by X-ray diffraction, and zero point charge determination. The chemically modified kaolinite samples showed modification of its physical–chemical properties including: specific area of 25.2–421.5 m 2 g −1 for K 1 and K 1-DS/APS, and 24.7–425.9 m 2 g −1 for K 2 and K 2-DS/APS. New d 0 0 1 values of 1.313 and 1.319 nm for the modified kaolinites K 1-DS/APS and K 2-DS/APS, respectively, were obtained. From electrical property investigations an increase in electric permittivity was observed for real ( ɛ |) and imaginary ( ɛ ||) at low frequencies, which are probably related to the interlayer molecules. The energetic effect caused by mercury cation adsorption was determined through calorimetric titration at the solid–liquid interface and gave net thermal effects that enabled the calculation of the exothermic enthalpic values and the equilibrium constant. From these values negative Gibbs free energy and positive entropy were calculated and this set of thermodynamic data is favorable for mercury/basic center interaction at the solid/liquid interface.

Uncertainties of geochemical modeling during CO2 sequestration applying batch equilibrium calculations

One of the uncertainties in the field of carbon dioxide capture and storage (CCS) is caused by the parameterization of geochemical models. The application of geochemical models contributes significantly to calculate the fate of the CO2 after its injection. The choice of the thermodynamic database used, the selection of the secondary mineral assemblage as well as the option to calculate pressure dependent equilibrium constants influence the CO2 trapping potential and trapping mechanism. Scenario analyses were conducted applying a geochemical batch equilibrium model for a virtual CO2 injection into a saline Keuper aquifer. The amount of CO2 which could be trapped in the formation water and in the form of carbonates was calculated using the model code PHREEQC. Thereby, four thermodynamic datasets were used to calculate the thermodynamic equilibria. Furthermore, the equilibrium constants were re-calculated with the code SUPCRT92, which also applied a pressure correction to the equilibrium constants. Varying the thermodynamic database caused a range of 61% in the amount of trapped CO2 calculated. Simultaneously, the assemblage of secondary minerals was varied, and the potential secondary minerals dawsonite and K-mica were included in several scenarios. The selection of the secondary mineral assemblage caused a range of 74% in the calculated amount of trapped CO2. Correcting the equilibrium constants with respect to a pressure of 125 bars had an influence of 11% on the amount of trapped CO2. This illustrates the need for incorporating sensitivity analyses into reaction pathway modeling.

CO 2–water–basalt interaction. Numerical simulation of low temperature CO 2 sequestration into basalts

The interaction between CO 2-rich waters and basaltic glass was studied using reaction path modeling in order to get insight into the water–rock reaction process including secondary mineral composition, water chemistry and mass transfer as a function of CO 2 concentration and reaction progress ( ξ). The calculations were carried out at 25–90 °C and pCO 2 to 30 bars and the results were compared to recent experimental observations and natural systems. A thermodynamic dataset was compiled from 25 to 300 °C in order to simulate mineral saturations relevant to basalt alteration in CO 2-rich environment including revised key aqueous species for mineral dissolution reactions and apparent Gibbs energies for clay and carbonate solid solutions observed to form in nature. The dissolution of basaltic glass in CO 2-rich waters was found to be incongruent with the overall water composition and secondary mineral formation depending on reaction progress and pH. Under mildly acid conditions in CO 2 enriched waters (pH <6.5), SiO 2 and simple Al–Si minerals, Ca–Mg–Fe smectites and Ca–Mg–Fe carbonates predominated. Iron, Al and Si were immobile whereas the Mg and Ca mobility depended on the mass of carbonate formed and water pH. Upon quantitative CO 2 mineralization, the pH increased to >8 resulting in Ca–Mg–Fe smectite, zeolites and calcite formation, reducing the mobility of most dissolved elements. The dominant factor determining the reaction path of basalt alteration and the associated element mobility was the pH of the water. In turn, the pH value was determined by the concentration of CO 2 and extent of reaction. The composition of the carbonates depended on the mobility of Ca, Mg and Fe. At pH <6.5, Fe was in the ferrous oxidation state resulting in the formation of Fe-rich carbonates with the incorporation of Ca and Mg. At pH >8, the mobility of Fe and Mg was limited due to the formation of clays whereas Ca was incorporated into calcite, zeolites and clays. Competing reactions between clays (Ca–Fe smectites) and carbonates at low pH, and zeolites and clays (Mg–Fe smectites) and carbonates at high pH, controlled the availability of Ca, Mg and Fe, playing a key role for low temperature CO 2 mineralization and sequestration into basalts. Several problems of the present model point to the need of improvement in future work. The determinant factors linking time to low temperature reaction path modeling may not only be controlled by the primary dissolving phase, which presents challenges concerning non-stoichiometric dissolution, the leached layer model and reactive surface area, but may include secondary mineral precipitation kinetics as rate limiting step for specific reactions such as retrieved from the present reaction path study.

Thermodynamic assessment of the ordered B2 phase in the Ti–V–Cr–Al quaternary system

Thermodynamic assessment of the ordered B2 phase in the quaternary Ti–V–Cr–Al system is carried out. A set of self-consistent thermodynamic parameters is presented. A two-sublattice model (Al,Cr,Ti,V ) 0.5: (Al,Cr,Ti,V ) 0.5 is used. The predicted phase equilibria and order/disorder transformation temperature are in good agreement with experimental information, both in the Ti–V–Cr–Al quaternary and in the important binary and ternary subsystems. The thermodynamic dataset can be used to predict compositions which are prone to the order/disorder reaction.

Structural, sorption and thermodynamic correlations from a layered barium phenylarsonate/n-alkyldiamine system

The barium phenylarsonate compound, Ba(HO 3AsC 6H 5) 2·2H 2O, has the ability to intercalate n-alkyldiamine molecules, H 2N(CH 2) n NH 2 ( n=2–5). The amount intercalated ( n f) from a batchwise procedure and the variation of the original basal distance ( d) of 1245 ppm determined through X-ray diffractions, gave linear correlations as a function of the number of carbon atoms in the aliphatic chain ( n c): n f=(2.66±0.06)−(0.13±0.02) n c and d=(2168±65)+(114±14) n c. The intercalation process was calorimetrically followed to give exothermic enthalpy and negative Gibbs energy, reflecting spontaneous intercalation reactions at the solid/liquid interface. The displacement of solvent molecules bonded to amine and of those on the matrix during the intercalation increases the disorder to result in positive entropy, giving a favorable set of thermodynamic data for this system.

An improved and extended internally consistent thermodynamic dataset for phases of petrological interest, involving a new equation of state for solids

The thermodynamic properties of 254 end-members, including 210 mineral end-members, 18 silicate liquid end-members and 26 aqueous fluid species are presented in a revised and updated internally consistent thermodynamic data set. The PVT properties of the data set phases are now based on a modified Tait equation of state (EOS) for the solids and the Pitzer & Sterner (1995) equation for gaseous components. Thermal expansion and compressibility are linked within the modified Tait EOS (TEOS) by a thermal pressure formulation using an Einstein temperature to model the temperature dependence of both the thermal expansion and bulk modulus in a consistent way. The new EOS has led to improved fitting of the phase equilibrium experiments. Many new end-members have been added, including several deep mantle phases and, for the first time, sulphur-bearing minerals. Silicate liquid end-members are in good agreement with both phase equilibrium experiments and measured heat of melting. The new dataset considerably enhances the capabilities for thermodynamic calculation on rocks, melts and aqueous fluids under crustal to deep mantle conditions. Implementations are already available in thermocalc to take advantage of the new data set and its methodologies, as illustrated by example calculations on sapphirine-bearing equilibria, sulphur-bearing equilibria and calculations to 300 kbar and 2000 °C to extend to lower mantle conditions.

Thermodynamic assessment of Au–La and Au–Er binary systems

Phase relationships in Au–La and Au–Er binary systems have been thermodynamically assessed by using the CALPHAD technique. The existing thermodynamic descriptions of the systems were improved by incorporating the ab initio calculated enthalpies of formation of the intermetallic compounds, except for the Au 51La 14 and Au 10Er 7 phases. All the binary intermetallic compounds were treated as stoichiometric phases, while the solution phases, including liquid, fcc, bcc, and dhcp, were treated as substitutional solution phases and the excess Gibbs energies were formulated with Redlich–Kister polynomial function. As a result, two self-consist thermodynamic data sets for describing the Au–La and Au–Er binary systems were obtained.

Effects of the variances of input parameters on water-mineral interactions during CO2 sequestration modeling

The mineral fixation of CO2 has a significant but highly varying relevance in carbon capture and storage (CCS) models. One reason is the impact of the minerals' concentrations, but the choice of the thermodynamic database on which the geochemical model calculations are based, has probably an equivalent or even more important impact on the model results. In this example, natural groundwater and a mineral assemblage consisting of calcite, dolomite, albite, and K-feldspar in two different concentrations were used to perform scenario simulations with the geochemical model PHREEQC. The four different thermodynamic datasets phreeqc.dat, wateq4f.dat, llnl.dat, and minteq.dat were used to calculate the amount of CO2 which could be fixed through the reactions with the described minerals. In the simulations using low reactive mineral concentrations (1-2.5 wt%), the range of the amount of fixed CO2 in the mineral and dissolved phases lies between 0.29 and 0.31 mol/kgw for the four chosen thermodynamic databases, which reflects the complete transformation of albite and K-feldspar to secondary minerals in all the simulations and only minor differences in the amounts of dissolved calcite and dolomite. On the other hand, the amount of fixed CO2 shows a variance of between 1.51 and 2.17 mol/kgw when using high reactive mineral concentrations (10-25 wt%). Especially the transformation of the K-feldspar depended significantly on the chosen thermodynamic database which affected the calculated product minerals of the reaction. Using the phreeqc.dat, the wateq4f.dat, and the minteq.dat databases, the amount of CO2 fixation due to its reaction with K-feldspar is up to six times larger than the amount calculated with the llnl.dat database. It is currently not clearly possible to decide which thermodynamic database should be used to receive the most realistic modeling results. Consequently, the uncertainty in the modeling results due to varying thermodynamic databases should be regarded in addition to the uncertainty resulting from factors like the heterogeneous distribution of mineral phases in the aquifers. It still has to be discussed whether a risk-based approach offers a secure way of modeling CCS related scenarios or whether worst-case scenarios have to be applied.

The influence of magnetic and chemical ordering on the phase diagram of Cr–Fe–Ni

A thermodynamic dataset for the ternary system Cr–Fe–Ni which has been reported in the literature for the range from medium to high temperatures has been supplemented with datasets from the binary sub-systems at lower temperatures. The magnetic and the chemical ordering transitions which are known from the binary Fe–Ni system were extrapolated into the ternary system Cr–Fe–Ni. The phase diagram of Cr–Fe–Ni alloys at temperatures below 500 °C was predicted. The magnetic contribution to the Gibbs energy of Ni-rich alloys induces a miscibility gap which appears in the binary phase diagram of Fe–Ni as a small triangle-like field ending in a tricritical point. In the ternary system Cr–Fe–Ni the miscibility gap is present as a broad two-phase field in the vicinity of the composition FeNi 3. At lower temperatures this miscibility gap participates in a sequence of changing equilibria when it interferes with the chemically ordered L1 2 phase.

Arsenic Eh–pH diagrams at 25°C and 1 bar

A thermodynamic dataset for arsenic species in As–O–H–S–Fe–Ba system was compiled from the literature. Using this dataset, Eh–pH diagrams for the systems As–O–H, As–O–H–S, As–O–H–S–Fe, As–O–H–Ba, and As–O–H–S–Fe–Ba were constructed at 25°C and 1 bar. The inclusion of thioarsenite species in the systems As–O–H–S and As–O–H–S–Fe results in substantial differences from previously published Eh–pH diagrams. There are considerable differences in the thermodynamic properties for orpiment, realgar, scorodite, arsenopyrite, barium arsenate, and barium hydrogen arsenate, which result in vastly different stability fields when different values are adopted.

Exploring the favorable ion-exchange ability of phthalylated cellulose biopolymer using thermodynamic data

A phthalylated ion-exchange biopolymer was obtained by adding cellulose to molten phthalic anhydride in a quasi solvent-free procedure. Through this route 2.99 ± 0.07 mmol g −1 of pendant groups containing ester and carboxylic acid moieties were incorporated into the polymeric structure that was characterized by elemental analysis, solid-state carbon nuclear magnetic resonance (CP/MAS), infrared spectroscopy, X-ray diffraction, and thermogravimetry. The chemically modified polysaccharide is able to exchange cations from aqueous solution as demonstrated by batchwise methodology. The data were adjusted to a modified Langmuir equation to give 2.43 ± 0.12 and 2.26 ± 0.11 mmol g −1 for divalent cobalt and nickel cations, respectively. The net thermal effects obtained from calorimetric titration measurements were also adjusted to a modified Langmuir equation, and the enthalpy of the interaction was calculated to give endothermic values of 2.11 ± 0.28 and 2.50 ± 0.31 kJ mol −1 for these cations, respectively. The spontaneity of this ion-exchange process is reflected in negative Gibbs energy and with a contribution of positive entropic values. This set of thermodynamic data at the solid–liquid interface suggests a favorable ion-exchange process for this anchored biopolymer for cation exchange from the environment.

ChemInform Abstract: The Stereoelectronic Parameters of Phosphites. The Quantitative Analysis of Ligand Effects (QALE).

Through an analysis of pKa values for HPZ3+, ionization potentials (IP) for PZ3, νCO for η-Cp(CO)(PZ3)Fe(COMe)0, and E° (229 K) and ΔH° for the η-Cp(CO)(PZ3)Fe(COMe)+/0 couple, we determined the values of the three electronic parameters, χd, Ear and πp that are needed to describe the stereoelectronic properties of phosphites. The phenomenon we call the ‘aryl effect’, which is described by the parameter Ear, is apparently not restricted to phosphines bearing pendant aryl groups but applies to the phosphites. πp is a new parameter related to the π acidity of the phosphites. The phosphites studied are listed in terms of increasing π acidity: P(OMe)3 ≈ P(OEt)3 ≈ P(OBu)3 ≈ P(O-i-Bu)3 ≈ P(O-i-Pr)3 < P(OCH2CH2Cl)3 < P(O-p-XC6H4)3 < P(OCH2)3CEt (X = MeO, Me, H, Cl, CN). Using these electronic parameters, along with Tolman’s cone angle, we have now incorporated the phosphites into the QALE (quantitative analysis of ligand effects) model and analyzed 32 sets of spectroscopic, thermodynamic, and kinetic data mostly taken from the literature. The analyses give a median r2 value of 0.982.

ChemInform Abstract: Thermodynamics of Gold-Erbium Alloys.

Abstract Galvanic cells with CaF 2 as solid electrolytes were used to obtain the thermodynamic properties of the gold–erbium system between 973 and 1073 K. A complete set of thermodynamic data was obtained for the gold-rich solid solution and for the intermetallic compounds Au 4 Er, Au 3 Er, Au 2 Er, AuEr and AuEr 2 . The relative partial excess Gibbs energy of erbium at infinite dilution was determined to be −257 kJ/mol at 1073 K. Electronic and elastic effects are discussed in order to account for the pronounced deviations from ideality.

Thermodynamic Evaluation of the Si-C-Al-Y-O System for LPS-SiC Application

A thermodynamic dataset for the Si-C-Al-Y-O system was developed for calculations of heterogeneous phase equilibria and reactions in SiC-base engineering ceramics. The quinary system is of major interest for the understanding of the liquid phase sintering of silicon carbide ceramics using additives like alumina (Al2O3) and yttria (Y2O3). The thermodynamic dataset was developed by the CALPHAD method of thermodynamic optimization. Analytical descriptions for the Gibbs free energy functions of all phases in the Si-C-Al-Y-O system were assessed. The sublattice model using the compound energy formalism was used for the treatment of the solid phases. The liquid phase was described by using the partially ionic liquid model presented as (Al3+, Si4+, Y3+)P(O2−, SiO4 4−, Va, AlO3/2, SiO2, C)Q, which covers metallic liquid and oxide liquid as a single phase.

Enthalpy of formation of the La–Mg intermediate phases

The aim of this work is to complete the available set of thermodynamic data on the La–Mg system in order to get reliable optimisation of this system by the CALPHAD method. Indeed the CALPHAD method requires a large set of consistent input data including both phase diagram and thermodynamic data. The enthalpies of formation of the La–Mg intermediate compounds were determined at 298 K by means of solution calorimetry in liquid Sn in a Tian–Calvet calorimeter. In these experiments, the partial enthalpies of solution of the compounds at infinite dilution in liquid tin were measured at 665 K. The enthalpies of formation of LaMg, LaMg 2 and La 2Mg 17 compounds were also calculated at 0 K by density functional theory to compare experimental and calculated values.

Equilibriums between Cu, Fe, and Zn sulfides and oxides in chloride solution: A thermodynamic study

The results of thermodynamic modeling of equilibriums between Cu, Fe, and Zn sulfides and oxides pertaining to the Cu-Fe-Zn-S-O2 system in water and aqueous chloride solution are presented. The system comprises solid phases of constant composition: pyrite, pyrrhotite, hematite, magnetite, wustite, γ-iron, chalcocite, covellite, cuprite, native copper, chalcopyrite, and bornite, as well as more than 100 ions, complexes, and molecules in an aqueous solution. The GIBBS program with the UNITHERM thermodynamic dataset used in calculations allows numerical analysis of phase assemblages in a dry system and in equilibrium with an aqueous solution. How the temperature, pressure, and the composition of the solution in the system opened for oxygen and sulfur affects the composition of phase assemblages was considered in temperature and pressure ranges of 50–350 C and 100–1000 bar, respectively. Decrease in temperature leads to a shift in stability fields of the studied phases toward the region of elevated oxygen and sulfur partial pressures. Variation of temperature is an important factor affecting precipitation of ore minerals, primarily, Cu- and Zn-bearing. The calculation results are presented in tables and diagrams. Each point in the $$ (\log m_{S_{tot} } - \log f_{O_2 } ) $$ diagram is characterized by a single possible assemblage of phases equilibrated with a solution of the given composition within the considered temperature and pressure range. Since the composition of the mineral assemblage is controlled by physicochemical conditions at the moment of mineral formation, comparison of the calculation results with mineral assemblages at ore deposits makes it possible to estimate the parameters of ore deposition at the early stage of investigation, including oxygen and sulfur activity and, occasionally, the composition and salinity of the solution. These parameters control the formation of such assemblages.

Ab initio derivation of a dataset of real temperature thermodynamic properties: Case study with SiC

A wholly ab initio method for deriving chemical thermodynamic data for inorganic crystals is a useful tool for theoretical research in material science. In this work, all electron density functional computations together with phonon vibrational analysis were used to derive thermodynamic profiles of two polytypes of SiC (3C and 2H) at real temperatures. This included standard Gibbs free energy of formation () and enthalpy of formation () values from 0 to 1000 K. Ground state properties were computed by the full potential linearized augmented plane wave method. Temperature effects were obtained by direct method computation of harmonic vibrations. To obtain and similar computations were also carried out for the reference state elements, Si (diamond) and C (graphite). Derived values include entropy, specific heat, enthalpy increment with temperature, absolute total enthalpy, internal energy and free energy, standard enthalpy of formation and standard free energy of formation for temperatures from 0 to 1000 K. Computed values are in very good agreement with the experimental data. This study demonstrates the utility of ab initio methods for deriving a thermodynamic data set.

A new formulation of garnet–clinopyroxene geothermometer based on accumulation and statistical analysis of a large experimental data set

AbstractPublished experimental data including garnet and clinopyroxene as run products were used to develop a new formulation of the garnet–clinopyroxene geothermometer based on 333 garnet–clinopyroxene pairs. Only experiments with graphite capsules were selected because of difficulty in estimating the Fe3+ content of clinopyroxene. For the calibration, a published subregular‐solution model was adopted to express the non‐ideality of garnet. The magnitude of the Fe–Mg excess interaction parameter for clinopyroxene (WFeMgCpx), and differences in enthalpy and entropy of the Fe–Mg exchange reaction were regressed from the accumulated experimental data set. As a result, a markedly negative value was obtained for the Fe–Mg excess interaction parameter of clinopyroxene (WFeMgCpx = − 3843 J mol−1). The pressure correction is simply treated as linear, and the difference in volume of the Fe–Mg exchange reaction was calculated from a published thermodynamic data set and fixed to be −120.72 (J kbar−1 mol−1). The regressed and obtained thermometer formulation is as follows: image where T = temperature, P = pressure (kbar), A = 0.5 Xgrs (Xprp − Xalm − Xsps), B = 0.5 Xgrs (Xprp − Xalm + Xsps), C = 0.5 (Xgrs + Xsps) (Xprp − Xalm), Xprp = Mg/(Fe2+ + Mn + Mg + Ca)Grt, Xalm = Fe/(Fe2+ + Mn + Mg + Ca)Grt, Xsps = Mn/(Fe2+ + Mn + Mg + Ca)Grt, Xgrs = Ca/(Fe2+ + Mn + Mg + Ca)Grt, XMgCpx = Mg/(Al + Fetotal + Mg)Cpx, XFeCpx = Fe2+/(Al + Fetotal + Mg)Cpx, KD = (Fe2+/Mg)Grt/(Fe2+/Mg)Cpx, Grt = garnet, Cpx = clinopyroxene. A test of this new formulation to the accumulated data gave results that are concordant with the experimental temperatures over the whole range of the experimental temperatures (800–1820 °C), with a standard deviation (1 sigma) of 74 °C. Previous formulations of the thermometer are inconsistent with the accumulated data set; they underestimate temperatures by about 100 °C at &gt;1300 °C and overestimate by 100–200 °C at &lt;1300 °C. In addition, they tend to overestimate temperatures for high‐Ca garnet (Xgrs ≈ 0.30–0.50). This new formulation has been tested against previous formulations of the thermometer by application to natural eclogites. This gave temperatures some 20–100 °C lower than previous formulations.

Thermodynamic modeling of the Al 2O 3–B 2O 3–SiO 2 system

A complete literature review, critical evaluation, and thermodynamic modeling of the phase diagrams and thermodynamic properties of all oxide phases in the ternary Al 2O 3–B 2O 3–SiO 2 system at 1 bar pressure are presented. The molten oxide phase is described by the Modified Quasichemical Model and the Gibbs energy of the mullite solid solution is modeled using the Compound Energy Formalism. A set of optimized internally consistent thermodynamic functions for all the phases is presented. With the thermodynamic dataset, all available and reliable thermodynamic and phase equilibrium data can be reproduced within experimental error limits from 25 °C to above the liquidus temperatures. In addition, the reasonable predictions obtained for phase relations in the experimentally unexplored composition ranges suggest that the thermodynamic database can be used along with appropriate Gibbs energy minimization routines to calculate thermodynamic properties, phase equilibria, and phase diagrams of interest.

Thermodynamics and Constitution of Mg-Al-Ca-Sr-Mn Alloys: Part II. Procedure for Multicomponent Key Sample Selection and Application to the Mg-Al-Ca-Sr and Mg-Al-Ca-Sr-Mn Systems

A procedure is suggested to identify key sample compositions in n-component alloys, providing the most crucial information with limited experimental effort. The proposed algorithm furthermore establishes the exact type of reaction equation of the (n + 1) phase invariant equilibria. Predictive calculations of phase equilibria in quaternary Mg-Al-Ca-Sr and quinary Mg-Al-Ca-Sr-Mn alloys are performed based on elaborate binary and ternary thermodynamic descriptions. Experimental work, using key samples and Mg-rich alloys, demonstrates the viability of the current approach in validating the predictions. Finally, the impact of using more or less elaborate ternary data is quantitatively exemplified for the quinary system Mg-Al-Ca-Sr-Mn by a comparison of different thermodynamic data sets.