Molar Gibbs Free Energy Change Research Articles

Influence of polyvinyl alcohol coated porous Al2O3 ceramic waste particles on cement properties in geothermal applications

To improve the low strength of the existing geothermal temporary sealing cement (GTSC) and figure out the influence of PACW on cement performances in geothermal applications, the hard porous Al2O3 ceramic waste (PACW) was introduced into oil well cement. The water-soluble PVA was coated on PACW particles to wrap the porous ceramic at relatively low temperature for geothermal drilling, and dissolve in water at ≥ 90 ℃ for hot water flow. The compressive strength, hydrates, pore structures and interface transition zone of cement with raw or modified PACW were tested. The results showed that 10% raw and modified PACW enhanced the compressive strength of oil well cement by 57.69% and 60.31% respectively, during the 90 ℃ water immersing. For the cement containing 10% raw and modified PACW, thermal weight loss related to degradation of hydrates and CH increased, meso pores fraction rose to 52.73% and 51.93 % respectively, and the deeper etch pits on surfaces of the mineral suggested the promoting effect of PACW on cement hydration. The promoted cement hydration and formed hydrates with their filling effect contributed to the cement strength enhancement. As the thermal weight loss attributed to AFm increased after immersion, the thermodynamic parameters of the possible transformation reaction of AFt to AFm were calculated. The standard molar Gibbs free energy change of the reactions are negative, and microstructure images showed that the PACW surface was covered by lots of flaky AFm crisscrossed with large hexagonal AFt crystals, proving that the alumina in PACW participated in and promoted the transformation of AFt to AFm. In addition to reservoir protection, simplifying construction procedures and reducing the time cost of geothermal development, the high-strength GTSC will further strengthen the hole wall and reduce the risk of borehole collapse.

Solubility measurement, correlation, and dissolution thermodynamics of 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane · 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (2HNIW·HMX) co-crystal in two binary solvent mixtures

The solubility of 2HNIW·HMX co-crystal in two binary solvent mixtures (ethanol + methyl acetate, and 1,2-dichloroethane + methyl acetate) was measured by gravimetric method at various temperatures (283.15, 288.15, 293.15, 298.15, 303.15, 308.15, 313.15 and 318.15 K) under atmospheric pressure (0.1 MPa). The experimental results revealed that the solubility for co-crystal in binary solvent mixtures is a simple function of ethanol (or 1,2-dichloroethane) mass fraction and temperature, which decreased with increasing temperature and mass fraction of ethanol (or 1,2-dichloroethane) in the binary solvent mixtures. The solubility of 2HNIW·HMX co-crystal was correlated with the modified Apelblat equation, CNIBS/R-K model, Jouyban-Acree-van't Hoff model, and Jouyban-Acree-Apelblat model. The fitting results demonstrate that the modified Apelblat model and CNIBS/R-K model provided a better correlation with the experimental results than the other models. Furthermore, the van’t Hoff equation was used to study the thermodynamic properties of the 2HNIW·HMX co-crystal dissolution process, including the apparent molar enthalpy change (ΔdisH°), the apparent molar entropy change (ΔdisS°), and the apparent molar Gibbs free energy change (ΔdisG°). The results show that the dissolution of the co-crystal in the selected binary solvent mixture is an exothermic process. The experimental and calculated solubility data and thermodynamic properties of the 2HNIW·HMX co-crystal would be helpful for selecting the appropriate solvent system for the reaction, crystallization, and purification of the 2HNIW·HMX co-crystal.

A thermodynamic approach to understand the partitioning of tetracycline family antibiotics in individual and mixed micellar systems

Micelle-mediated drug delivery is an efficient and smart way of delivering drugs to the target sites. This method of drug delivery increases the concentration of the drugs specifically to the affected tissues/organs and hence increases the bioavailability of the drug and reduces the side-effects of the drug. Quantitative understanding of the mechanism of partitioning of drugs in micellar structures is crucial for developing guidelines to design effective drug delivery systems. In this background, we have done quantitative studies of the mechanism of partitioning of four drugs doxycycline, minocycline, tetracycline and oxytetracycline which belong to tetracycline family of antibiotics in the HTAB, TX-100 and mixed surfactant micellar system using isothermal titration calorimetry (ITC). The insights into the partitioning mechanisms have been investigated in a temperature range T = 288.15 K–310.15 K in terms of the values of standard molar enthalpy, standard molar entropy, the standard molar Gibbs free-energy change, and stoichiometry of partitioning. The thermodynamic parameters for the interaction of the drugs with the surfactants suggest involvement of ionic/H-bonding as well as hydrophobic interactions between the drugs and the surfactant micelles and monomers. The effects of the drugs on the critical micellar concentration of the surfactants are studied using ITC and fluorescence spectroscopy. The results are essential in establishing structure-properties-energetics correlations and will help in designing enhanced strategies for improved drug delivery systems.

Effect of the particle size on the reactivity of MgO-Al2O3 hydrating mixtures: A long-term kinetic investigation of hydrotalcite synthesis

Hydrotalcite-like compounds (HTlc) are commonly known anionic clay that may potentially be used as hydraulic binder component for refractory materials, ion exchangers, catalyst or carrier of bioactive molecules. According to current state of knowledge LDH (Layered Double Hydroxides) can be synthesized using various methods including mechanochemical synthesis, hydrothermal precipitation, sol–gel syntheses and coprecipitation method. Research on the synthesis of hydrotalcite in the mixture of oxide powders of Al2O3 and MgO cured under specific conditions is particularly important in case of the determination of the relationship between the type (susceptibility to hydration, grain size and specific surface area) of initial powders and reaction kinetics. As a result, the hydration of an equimolar mixture of magnesium and alumina oxides nano- or micro-powders has been proven to be an effective low temperature method of synthesis well crystallized MgAl LDH with highly ordered structures. This investigations clearly show that the kinetics of hydration is influenced only by properties of aluminium oxide as initial powder. The synthesis of Mg6Al2CO3(OH)16∙4H2O as a result of hydration is associated with composite matrix formation which firstly consist of partly reacted initial powders bonded by hydration products. The synthesis of Mg6Al2CO3(OH)16∙4H2O was discussed in terms of molar Gibbs free energy change of reactions within the MgO-Al2O3-CO2-H2O system. The calculated formation Gibbs energy was negative, when Mg(OH)2 was formed as an intermediate product. The standard Gibbs free energies of hydrotalcite formation was estimated based on the simple mechanical mixture model that treats Mg6Al2CO3(OH)16∙4H2O as mixtures of simple oxides. Thermodynamic calculations were performed assuming an equilibrium state between aqueous solutions and corresponding precipitates after synthesis.

Real-Time Monitoring of the Thermal Effect for the Redox Flow Battery by an Infrared Thermal Imaging Technology

In this study, a new monitoring method was developed, titled infrared thermal imaging technology, which can effectively evaluate the thermal effect of the charge-discharge test in the vanadium/iodine redox flow battery (V/I RFB). The results show that the all-vanadium redox flow battery (all-V RFB) has a greater molar reaction Gibbs free energy change than that of the V/I RFB, representing a large thermal effect of the all-V RFB than the V/I RFB. The charge-discharge parameters, flow rate and current density, are important factors for inducing the thermal effect, because of the concentration polarization and the ohmic resistor. The new membrane (HS-SO3H) shows a high ion exchange capacity and a good ions crossover inhibitory for the V/I RFB system, and has a high coulomb efficiency that reaches 96%. The voltage efficiency was enhanced from 61% to 86% using the C-TiO2-Pd composite electrode as a cathode with the serpentine-type flow field for the V/I RFB. By adopting the high-resolution images of an infrared thermal imaging technology with the function of the temperature profile data, it is useful to evaluate the key components’ performance of the V/I RFB, and is a favorable candidate in the developing of the redox flow battery system.

Comparative thermodynamic analysis of CO2 based dimethyl carbonate synthesis routes

AbstractThe chemical equilibrium analysis of various possible reactions involved in the five CO2‐based routes for the synthesis of dimethyl carbonate (DMC), a green chemical reagent, was performed in the present study. The variation of the molar Gibbs free energy change with temperature for the major reactions of DMC synthesis in all five routes was studied in the specified temperature range of 298.15 K‐453.15 K and at both 1 bar and 28 bar pressures (1 bar = 105 Pa) to observe the thermodynamic favourability of all routes. To observe the temperature effect, the molar heat capacities for various compounds were estimated in terms of temperature. A second‐order group additivity method called the Ruzicka‐Domalski method was used to estimate these heat capacity values. The major reactions of DMC synthesis in urea methanolysis, EC transesterification, PC transesterification, and direct CO2 synthesis routes were compared by investigating the effect of temperature (in the range of 298.15 K‐453.15 K) on the chemical equilibrium constants and the equilibrium conversions of methanol at a constant pressure of 28 bar. The one‐pot propylene oxide (PO) synthesis route was observed to be better among all the five CO2 based routes when it was compared with respect to values of the chemical equilibrium constant and equilibrium conversion of methanol at standard conditions. The reliability of the EC transesterification route was found better among all the routes at initial conditions (T = 298.15 K; P = 28 bar). While the urea methanolysis route was found as least favourable at initial conditions.

Utilization of Biomass Fly Ash for Improving Quality of Organic Dye-Contaminated Water.

Development of innovative methodologies to convert biomass ash into useful materials is essential to sustain the growing use of biomass for energy production. Herein, a simple chemical modification approach is employed to functionalize biomass fly ash (BFA) with 3-aminopropyltriethoxy silane (APTES) to develop an inexpensive and efficient adsorbent for water remediation. The amine-functionalized BFA (BFA–APTES) was fully characterized by employing a range of characterization techniques. Adsorption behavior of BFA–APTES was evaluated against two anionic dyes, namely, alizarin red S (ARS) and bromothymol blue (BTB). In the course of experimental data analysis, the computation tools of data fitting for linear and nonlinear form of Langmuir, Freundlich, and the modified Langmuir–Freundlich adsorption isotherms were used with the aid of Matlab R2019b. In order to highlight the misuse of linearization of adsorption models, the sum of the squares of residues (SSE) values obtained from nonlinear models are compared with R2 values obtained from the linear regression. The accuracy of the data fitting was checked by the use of SSE as an error function instead of the coefficient of determination, R2. The dye adsorption capacity of BFA–APTES was also compared with the nonfunctionalized BFA. The maximum adsorption capacities of BFA–APTES for ARS and BTB dye molecules were calculated to be around 13.42 and 15.44 mg/g, respectively. This value is approximately 2–3 times higher than the pristine BFA. A reasonable agreement between the calculated and experimental values of qe obtained from the nonlinear form of kinetic models verified the importance of using equations in their original form. The experimentally calculated thermodynamic parameters including molar standard Gibbs free energy (ΔadGm0) and molar standard enthalpy change (ΔadHm0) reflected that the process of adsorption of dye molecules on the BFA–APTES adsorbent was spontaneous and exothermic in nature. Moreover, the used BFA–APTES adsorbent could be regenerated and reused for several cycles with significant dye adsorption capacity. The remediation capability of the BFA–APTES adsorbent against ARS dye was also demonstrated by packing a small column filled with the BFA–APTES adsorbent and passing a solution of ARS through it. Overall, we provide a simple and scalable route to convert BFA into an efficient adsorbent for water remediation applications.

Theoretical Study of Radical-Molecule Reactions with Negative Activation Energies in Combustion: Hydroxyl Radical Addition to Alkenes.

Many of the radical–molecule reactions are nonelementary reactions with negative activation energies, which usually proceed through two steps. They exist extensively in the atmospheric chemistry and hydrocarbon fuel combustion, so they are extensively studied both theoretically and experimentally. At the same time, various models, such as a two transition state model, a steady-state model, an equilibrium-state model, and a direct elementary dynamics model are proposed to get the kinetic parameters for the overall reaction. In this paper, a conversion temperature TC1 is defined as the temperature at which the standard molar Gibbs free energy change of the formation of the reaction complex is equal to zero, and it is found that when T ≫ TC1, the direct elementary dynamics model with an inclusion of the tunneling correction of the second step reaction is applicable to calculate the overall reaction rate constants for this kind of reaction system. The reaction class of hydroxyl radical addition to alkenes is chosen as the objects of this study, five reactions are chosen as the representative for the reaction class, and their single-point energies are calculated using the method of CCSD(T)/CBS, and it is shown that the highest conversion temperature for the five reactions is 139.89 K, far below the usual initial low-temperature (550 K) oxidation chemistry of hydrocarbon fuels; therefore, the steady-state approximation method is applicable. All geometry optimizations are performed at the BH&HLYP/6-311+G(d,p) level, and the result shows that the geometric parameters in the reaction centers are conserved; hence, the isodesmic reaction method is applicable to this reaction class. To validate the accuracy of this scheme, a comparison of electronic energy difference at the BH&HLYP/6-311+G(d,p) level and the corrected electronic energy difference with the electronic energy difference at the CCSD(T)/CBS level is performed for the five representative reactions, and it is shown that the maximum absolute deviation of electronic energy difference can be reduced from 2.54 kcal·mol–1 before correction to 0.58 kcal·mol–1 after correction, indicating that the isodesmic reaction method is applicable for the accurate calculation of the kinetic parameters for large-size molecular systems with a negative activation energy reaction. The overall rate constants for 44 reactions of the reaction class of hydroxyl radical addition to alkenes are calculated using the transition-state theory in combination with the isodesmic correction scheme, and high-pressure limit rate rules for the reaction class are developed. In addition, the thermodynamic parameter is calculated and the results indicate that our dynamics model is applicable for our studied reaction class. A chemical kinetic modeling and sensitivity analysis using the calculated kinetic data is performed for the combustion of ethene, and the results indicate the studied reaction is important for the low-to-medium temperature combustion modeling of ethene.

SYNTHESIS, CHARACTERIZATION, ADSORPTION AND THERMODYNAMIC STUDIES OF PURE AND BINARY CO2-N2 MIXTURES ON OXYGEN ENRICHED NANOSTRUCTURED CARBON ADSORBENTS

Abstract Oxygen enriched porous carbons have been synthesized by a nanocasting technique using mesoporous zeolite as template and epoxy resin as precursor. Characterization results show the effect of the nanocasting technique on the development of heterogeneous surface, high basicity, and high surface area of 686.37 m2g-1, beneficial for CO2 adsorption. Pure component adsorption isotherms were correlated with Langmuir, Sips, and dual-site Langmuir (DSL) models and found that Sips and DSL isotherm models fitted well, indicating thre heterogeneous nature of the adsorbent surface. Dynamic breakthrough data for the binary system CO2-N2 were obtained using a fixed-bed column at different adsorption temperatures (30-100 °C) and CO2 feed concentrations (5-12.5% by volume). The developed adsorbent shows high adsorption capacity with complete regenerability over four adsorption/desorption cycles. Prediction of binary components (CO2-N2) was made by using extended Sips, extended DSL and IAST (ideal adsorbed solution theory) by utilizing pure component adsorption isotherm data. Experimental and predicted equilibrium data were compared with breakthrough curve data and it was found that the extended forms (Sips and DSL) indicated under-predicted CO2 adsorption equilibria because of differences in adsorptive strengths of CO2 and N2 molecules. Also, adsorption equilibria were closely predicted using IAST theory. Asymmetric x-y diagrams from Raoult’s law indicated positive deviation, implying that as the CO2 gas phase molar fraction increases, total adsorbed amounts increase. Negative values of molar Gibbs free energy change suggested feasibility of the adsorption process. Formation of a more ordered configuration of CO2 molecules on the adsorbent surface was seen as a higher heat of adsorption was exhibited for CO2 as compared to N2.

Critical Assessment of Activities of Structural Units in Fe–Al Binary Melts Based on the Atom and Molecule Coexistence Theory

AbstractA thermodynamic model for calculating the mass action concentrations{N_i}of structural units in Fe–Al binary melts based on the atom–molecule coexistence theory,i. e., AMCT–{N_i}model, has been developed and verified to be valid by comparing with reported activities{a_{{\rm{R, }}i}}of both Al and Fe relative to pure liquid as standard state in Fe–Al binary melts over a temperature range from 1823 to 1973 K (1550 to 1700 °C). Furthermore, Raoultian activity coefficients\gamma _i^0of both Al and Fe in the Fe-rich corner or Al-rich corner of Fe–Al binary melts as well as the standard molar Gibbs-free energy changes{\Delta _{{\rm{sol}}}}G_{{\rm{m, }}i{\rm{(l)}} \to {{{\rm{[}}i{\rm{]}}}_{{\rm{ [ \% }}i]{\rm{ = 1}}{\rm{. 0}}}}}^{\Theta {\rm{, \% }}}of dissolved Al or Fe for forming [% Al] or [% Fe] as 1.0 in Fe–Al binary melts have also been determined by the developed AMCT–{N_i}model and verified to be accurate.The reported activities{a_{{\rm{R, }}i}}of both Al and Fe from the literature can be well reproduced by calculated mass action concentrations{N_i}of free Al and free Fe in Fe–Al binary melts. A small effect of changing temperature from 1823 to 1973 K (1550 to 1700 °C) on reaction abilities of both Al and Fe from the available literature is also confirmed by calculated mass action concentrations{N_i}of free Al and free Fe in Fe–Al binary melts. The obtained activity coefficients{\gamma _i}of both Al and Fe in Fe–Al binary melts can be described by a quadratic polynomial function and a cubic polynomial function, respectively. Furthermore, accurate expressions of Raoultian activity coefficients\gamma _i^0of both Al and Fe in Fe-rich corner or Al-rich corner of Fe–Al binary melts are also obtained as\ln \gamma _{{\rm{Al}}}^0 = - {\rm{9, 646}}{\rm{. 5}}/T{\rm{ + 2}}{\rm{. 196}}and\ln \gamma _{{\rm{Fe}}}^0 = - {\rm{6, 799}}{\rm{. 1}}/T - {\rm{0}}{\rm{. 01367}}, respectively. In addition, expressions of the first-order activity interaction coefficients\varepsilon _i^iore_i^iorh_i^iof both Al and Fe coupled with three activity coefficients\gamma _i^{}orf_{ \% {\rm{, }}i}^{}orf_{{\rm{H, }}i}^{}relative to three standard states are also obtained from the developed AMCT–{N_i}model for Fe–Al binary melts.

Measurement and modelling of solubility data for bosentan in 1-propanol + water mixtures at various temperatures

ABSTRACTThe experimental solubility determination of bosentan (BST) in 1-propanol + water mixtures within temperature range, T = (293.15–313.15) K were performed by applying the shake-flask method. The solubility data were correlated by four cosolvency models, which are the Jouyban-Acree, Jouyban-Acree-van’t Hoff, modified Wilson, and Yalkowsky equations. The back-calculated solubility using the Jouyban-Acree-van’t Hoff equation presents better compatibility with the experimental data than those by the other models. Thermodynamic properties such as apparent molar enthalpy, entropy, and Gibbs free energy change of BST dissolution process in the binary (1-propanol + water) mixtures were also calculated which indicative of the inspontaneous process of dissolution.

Esterase activity and conformational changes of bovine serum albumin toward interaction with mephedrone: Spectroscopic and computational studies.

The present work is a brief overview of the effect of psychostimulant drug mephedrone hydrochloride (4MMC) on a transport protein, bovine serum albumin (BSA). The binding effect of 4MMC on BSA has been investigated by using UV-visible, steady-state fluorescence, time-resolved fluorescence, fluorescence resonance energy transfer, Fourier transform infrared, circular dichroism, and molecular docking method. 4-Methylmephedrone quenched the intrinsic fluorescence of BSA by static quenching mechanism, which was further confirmed by time-resolved fluorescence. The absorption spectrum of BSA in the presence of various concentrations of 4MMC reveals the change in the absorption bands of BSA-4MMC complex. The binding constant between 4MMC and BSA was calculated to be of the order of 104 Lmol-1 . The thermodynamic parameters such as molar enthalpy change (∆H), molar Gibbs free energy change (∆G), and molar entropy contribution (∆S) were obtained by the van't Hoff equation. The values obtained suggested that the binding mechanism was entropic driven and the major forces involved are hydrophobic in nature. The fluorescence resonance energy transfer result indicates the high probability of energy transfer from Trp residue of BSA to the 4MMC (r=2.01nm). Fourier transform infrared and CD results showed that 4MMC induced secondary structural changes in BSA. The esterase-like activity of BSA in presence of 4MMC further validated our CD results, confirming the distortion and change in functionality of protein upon binding with 4MMC. Molecular docking analysis showed that 4MMC principally bind at the II site (subdomain IIIA) of BSA.

Adsorption and thermodynamic studies of pure and binary CO2 and N2 gas components on nitrogen enriched nanostructured carbon adsorbents

Abstract Adsorption isotherms of pure components (CO2 and N2) on nitrogen enriched nanostructured carbon (UFZ-700) were evaluated at four different adsorption temperatures ranging from 303 to 373 K using a static volumetric analyzer. They were then correlated with the three pure component adsorption isotherm models namely Langmuir, Sips, and dual-site Langmuir (DSL) models. Binary components (CO2-N2) adsorption equilibria were then predicted by extending Sips and DSL equations empirically along with usage of ideal adsorbed solution theory. Further, it was compared with experimental data obtained from the breakthrough curves by various phase diagrams. Binary system breakthrough data were obtained at four different CO2 feed concentration and four adsorption temperatures (303–373 K) using a fixed-bed column. Sips and DSL adsorption isotherm models fitted well among three pure component adsorption isotherm models indicating energetically heterogeneous adsorbent surface. Because of the difference in adsorptive strengths of CO2 and N2 molecules, the models extended forms highly under-predicted the amount of CO2 adsorbed over the whole temperature and feed concentration range. Also, ideal adsorbed solution theory failed to describe the mixed-gas adsorption equilibria. With the increase in CO2 gas phase molar fraction, total adsorbed amounts were found to increase, deviation indicating positive from Raoult’s law with asymmetric x-y diagrams. Thermodynamic functions such as molar Gibbs free energy change, entropy change, and enthalpy change for the pure component system were numerically evaluated. They indicated the formation of more ordered configuration of CO2 molecules on the adsorbent surface and confirmed the feasibility of adsorption process.

Determination and correlation of solubility of linezolid form II in different pure and binary solvents

The solubility data of linezolid form II in five pure solvents (water, methanol, ethanol, 1-propanol, 2-propanol) and a binary (water + methanol) solvent were determined among the temperature range from 283.15 K to 318.15 K under atmospheric pressure. The results indicated that the solubility increased with the temperature increasing. Seven thermodynamic models were used here to correlate the experimental solubility data. Through the comparison of the experimental data in pure solvents with the calculated results, we found that the modified Apelblat equation fit the experimental data best. Furthermore, the density functional theory (DFT) calculations showed that the solubility in different solvents related to the interaction strength between the linezolid and the solvent molecules. Finally, the molar enthalpy change, molar entropy change and molar Gibbs free energy change of dissolution of linezolid in the different solvents were also calculated by van't Hoff equation in this paper.

Correlation and prediction of the solubility of the racemic tartaric acid–ethanol–water system with the NRTL model

The solubility data on solid–liquid equilibria (SLE) of racemic tartaric acid in ethanol+water mixtures were measured in the temperature range of (293.15 to 318.15) K at 0.1MPa by acid–base titration method. In the binary solvent mixtures the solubility of racemic tartaric acid increases with rising temperature and decreases with increasing ethanol content. The modified Apelblat equation, λh equation and CNIBS/R–K equations were applied to describe and predict the change tendency of solubility. Computational results show that the modified Apelblat equation is superior to the others. Furthermore, a predictive version of the NRTL model was proposed for the description of the non-ideality of the racemic tartaric acid–ethanol–water system. The predicted values were compared with the experimental data. The agreements are good. By using the van't Hoff equation the molar enthalpy, entropy and Gibbs free energy changes of solution were calculated. A linear ∆solH versus ∆solS compensation plot with a positive slope was obtained by means of enthalpy–entropy compensation effect.

Prediction model of sulphur distribution ratio between CaO–FeO–Fe2O3–Al2O3–P2O5 slags and liquid iron over large variation range of oxygen potential during secondary refining process of molten steel based on ion and molecule coexistence theory

A thermodynamic model for predicting sulphur distribution ratio LS between CaO–FeO–Fe2O3–Al2O3–P2O5 slags and liquid iron, i.e. the ion and molecule coexistence theory (IMCT)–LS model, has been developed for slags in a large variation range of slag oxidisation ability based on the IMCT. The developed IMCT–LS model has been verified with measured data of oxygen, phosphorus and sulphur distribution equilibria between the slags and liquid iron from the literature. The results indicate that the desulphurisation reaction is mainly controlled by reaction (CaO)+[S] = (CaS)+[O] in the reducing zone with the optimised standard molar Gibbs free energy change of ; the desulphurisation reaction is dominated by reaction (FeO)+[S] = (FeS)+[O] in the oxidising zone with the reported standard molar Gibbs free energy change of . The influence of CaO on the desulphurisation ability of the slags can be counteracted by that of FetO because higher CaO content corresponds to lower FetO content in the slags. An asymmetric V type relationship between sulphur distribution ratio LS and the mass action concentration ratio or or or , or the mass percentage ratio (%FeO)/(%CaO) or (%Fe2O3)/(%CaO) or (%FetO)/(%CaO) or the simplified complex basicity or optical basicity can be established for the slags equilibrated with liquid iron in a temperature range from 1811 to 1927 K (1538 to 1654°C). The abovementioned mass action concentration ratios or mass percentage ratios of various iron oxides to basic oxide CaO can be recommended to represent the comprehensive effect of iron oxides FetO and basic oxide CaO on desulphurisation ability of the slags.

Thermodynamic models for determination of the solubility of omeprazole sulfide in (ethanol + ethyl acetate) binary solvent mixtures

The solubility of omeprazole sulfide in (ethanol+ethyl acetate) binary solvent mixtures was measured within the temperature range from 277.65 to 333.15K. The experimental data were fitted using CNIBS/R–K equation and the Jouyban–Acree equation, respectively. All the two equations were proven to give good representations of the experimental values. Computational results showed that the CNIBS/R–K equation was superior to the other equation. The thermodynamic properties of the solution process, including the Gibbs free energy, enthalpy and entropy, were calculated by the van’t Hoff analysis. The values of both the enthalpy change and the standard molar Gibbs free energy change of solution were positive, which indicated that the process was endothermic.

Thermodynamic characterization of proflavine–DNA binding through microcalorimetric studies

The interaction of an important acridine dye, proflavine hydrochloride, with double stranded DNA was investigated using isothermal titration calorimetry and differential scanning calorimetry. The equilibrium constant for the binding reaction was calculated to be (1.60±0.04)·105·M−1 at T=298.15K. The binding of proflavine hydrochloride to DNA was favored by both negative enthalpy and positive entropy contributions to the Gibbs energy. The equilibrium constant for the binding reaction decreased with increasing temperature. The standard molar enthalpy change became increasingly negative while the standard molar entropy change became less positive with rise in temperature. However, the standard molar Gibbs free energy change varied marginally suggesting the occurrence of enthalpy–entropy compensation phenomenon. The binding reaction was dominated by non-polyelectrolytic forces which remained virtually unchanged at all the salt concentrations studied. The binding also significantly increased the thermal stability of DNA against thermal denaturation.

The stable polyiodides: Experimental and theoretical studies of formation mechanism

The structures of polyiodides have been extensively studied for long time, but it was rarely involved of the mechanism of polyiodide species formation in preparation. The tetraethylammonium polyiodides were chosen as model chemicals and prepared with different molar ratios of reactants in ethanol solvent, the products were analyzed by titration, Raman spectra and TGA/DTG/DSC analysis, with the increase of the molar ratios of reactants, the iodine contents of the products reached a constant value. Finally, only two stable structures, Et4NI3 (1, space group Cmca) and Et4NI7 (2, space group Cmca), were isolated by recrystallization of slow evaporating solvent(s). The thermal analysis of tetraethylammonium polyiodides showed that all tetraethylammonium polyiodides lost I2 together to become Et4NI3 firstly and then continue to decompose. The decomposition of Et4NI3 was not a simple process which Et4NI3 lost one iodine molecule and then became Et4NI. In addition, the thermodynamical properties of species (I2 and Et4NIx, x=1, 3, 5, 7) and the molar standard Gibbs free energy changes of reactions (ΔrGmθ), as well as the mechanism of tetraethylammonium polyiodides formation were interpreted by density functional theory (DFT) calculations. The calculations show that the solvent effects have impact on the reactions. Accordingly, a comparative study was carried out on the solid phase synthesis of Et4NI5 at 80°C and at molten state. Furthermore, the solid synthesis of Et4NI5 was characterized by variable temperature (−25°C∼150°C) Raman Spectrometer. The polyiodide components interconversion showed the discrete I5- could be formed in molten state. In short, what species of polyiodides crystallized from reactions in solutions are decided by the synergy between ΔrGm of reactions and Coulombic interactions etc. of polyiodide crystals.

Elucidating the energetics of the interaction of non-toxic dietary pigment curcumin with human serum albumin: A calorimetric study

Thermodynamic quantities for the interaction of the anticancer dietary pigment curcumin with human serum albumin were measured by using isothermal titration calorimetry. The equilibrium constant of the complex formation at T=293.15K was found to be (5.25±0.05)105M−1. The binding was exothermic with TΔS0=(24.82±0.01)kJ·mol−1, where ΔS0 is the standard molar entropy change and ΔHo=−(7.28±0.04)kJ·mol−1, where ΔHo is the standard molar enthalpy change. The stoichiometry of binding was established to be 1:1. The equilibrium constant decreased with increasing Na+ concentration. The equilibrium constant decreased from (5.25±0.05)·105M−1 to (2.88±0.03)·105M−1 by increasing the salt concentration from (10 to 50)mM. Both polyelectrolytic and non-polyelectrolytic forces contributed to the standard molar Gibbs free energy change. However the contribution from the latter was dominant and almost invariant at all Na+ concentrations. The negative standard molar heat capacity change along with significant enthalpy–entropy compensation suggests the involvement of multiple weak non-covalent forces in the binding process.