Thermodynamic Correlation Research Articles

Solubility Determination and Thermodynamic Correlation of 2-Ethoxybenzamide in 12 Pure Solvents from 288.15 to 328.15 K

The solubility of 2-ethoxybenzamide was measured in 12 pure solvents, namely, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, ethyl formate, methyl acetate, propyl acetate, n-butyl acetate, N, N-dime...

Evaluation of kinetic salt-enrichment behavior and separation performance of HFC-152a hydrate-based desalination using an experimental measurement and a thermodynamic correlation

Hydrate-based desalination (HBD), a type of freezing-based desalination, can concentrate salts of saline water and produce fresh water via hydrate crystal formation. In this study, the thermodynamic stability, crystallographic information, and kinetic growth behavior of HFC-152a hydrate were investigated to estimate the desalination efficiency of HBD. The phase equilibria revealed that the HFC-152a hydrate could be formed at a higher temperature in the presence of NaCl (0 wt%, 3.5 wt%, and 8.0 wt%) than the HFC-134a hydrate at 0.3 MPa. The hydration number of the HFC-152a hydrate (sI) was found to be 7.74 through the Rietveld refinement of the powder X-ray diffraction patterns, and it was also used to determine the dissociation enthalpy of the HFC-152a hydrate. The Hu-Lee-Sum correlation was employed to predict the equilibrium shift and hydrate depression temperature of both HFC-152a and HFC-134a hydrates in the presence of NaCl. Faster hydrate growth kinetics and higher hydrate conversion were observed for the HFC-152a hydrate in saline solutions despite the smaller initial driving force at 0.3 MPa and the subcooling temperature of 3 K. Additionally, to quantify the desalination efficiency of the HFC-152a HBD, the maximum achievable salinity and maximum water yield were examined using the HLS correlation. The salt-enrichment efficiency decreased with an increase in the initial salinity and increased with increasing the subcooling. The overall results indicate that HFC-152a is, potentially, a superior candidate for HBD. The novel approach examined in this study will be useful for assessing the desalination efficiency of the HBD process.

Determination and correlation of solubility and solution thermodynamics of 1, 2-diphenylethane in different pure solvents

The correlation of solubility and solution thermodynamics of 1,2- diphenylethane in different pure solvents has been studied. The mole fraction solubilities of 1, 2-diphenylethane in acetone, chloroform, dichloromethane, and ethanol increase with temperature. The mole fraction solubility in acetone, chloroform and dichloromethaneare much higher than that in ethanol and the mole fraction solubilities in chloroform and dichloromethane are higher than that in acetone. The solubility data were well correlated by the modified Apelblat,the semi-empirical Buchowski-Ksiazczak λh equation, and the ideal solution equation.The enthalpy, entropy and apparent free Gibbs energy of solution in different solvents were calculated. The dissolving process of 1,2-diphenylethane was endothermic, entropy-driving and not spontaneous.

Thermodynamic analysis and optimisation of double effect absorption type combined power and cooling cycle using LiBr-water as working fluid

In this work, the mathematical model and simulation of the series and parallel flow double effect absorption type combined power and cooling cycle (DACPC) has been done in Scilab (open source software) using highly accurate thermodynamic correlations available in the literature. Sensitivity analysis of the operating parameters of a cycle has been studied and it has been optimised using Scilab's inbuilt function 'optim' to get maximum exergy efficiency for given evaporator and absorber temperature. The DACPC has been compared with other combined power and cooling cycle from the literature and found that its exergy efficiency is significantly more by 7-41%. The data of optimised operating conditions is generated and it will be useful for designing the cycle for practical applications. The maximum exergy efficiency of DACPC is in a range of 60% to 65%.

Using digital twins and data analytics to make informed operational decisions – a centrifugal compressor case study

An Australian operator with an expansive portfolio of liquefied natural gas, pipeline gas and oil assets wanted to gain greater visibility of how their compressor fleet was operating. To help the operator gain a greater understanding of the performance of their assets, Worley Digital built digital twins of 17 of their compressors. This involved detailed first principle calculations supported by hundreds of thousands of offline simulations. This created the thermodynamic correlations necessary to accurately model the most important operating statistics surrounding each stage of those assets. We then used dimensional analysis and data analytics to benchmark the operation of these machines. This represents a hybrid approach; first principles engineering and simulation coupled with data science and analytics. A suite of tools was then delivered to the operator in their preferred real-time data analytics and visualisation platform, providing them with information about the efficiency of their compressors. They were then able to perform net present value calculations based on different operating and maintenance strategies. This gave them the detailed information they needed in order to be able to make more informed decisions. An example of this might be a decision to bring a scheduled maintenance activity forward based on the knowledge that there are net operational and financial incentives to do so. The resulting tool has proved extremely valuable, quantifying some business-critical metrics that have led to several financially impactful operational decisions.

Solubility of sulfadiazine in (acetonitrile + methanol) mixtures: Determination, correlation, dissolution thermodynamics and preferential solvation

The equilibrium solubility of sulfadiazine (SD, 3) in {acetonitrile (MeCN, 1) + methanol (MeOH, 2)} mixtures at nine temperatures from 278.15 K to 318.15 K has been determined and correlated by means of some well-known thermodynamic correlation models. Five models including van't Hoff, the mixture response surface (MRS), Jouyban-Acree, Jouyban-Acree-van't Hoff and the modified Wilson models were applied to mathematical solubility data modelling. The accuracy of each model is investigated by the mean relative deviations (MRD%) of the back-calculated solubility. All used models show a low MRD% values (< 8.0%) for the calculated data indicating a good correlation of sulfadiazine solubility data with the given mathematical models. By using the van't Hoff and Gibbs equations the respective apparent thermodynamic quantities of the dissolution and mixing processes, namely Gibbs energy, enthalpy, and entropy, were calculated. Non-linear enthalpy–entropy relationship was observed for SD in the plot of enthalpy vs. Gibbs energy exhibiting negative slope in the composition region 0.00 < w1 < 0.05 indicating entropy-driving mechanism for this transfer process, and variant but mainly positive slopes in the composition interval 0.05 < w1 < 0.30, indicating enthalpy-driving mechanism for these transfer processes. From w1 = 0.30 to neat MeCN a slope near zero is observed. Furthermore, the preferential solvation of SD by MeCN or MeOH was analysed by using the inverse Kirkwood-Buff integrals. Thus, SD is preferentially solvated by MeOH molecules in MeOH-rich mixtures.

Exact solution of the Gaudin model with Dzyaloshinsky–Moriya and Kaplan–Shekhtman–Entin–Wohlman–Aharony interactions* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11847245 and 11874393).

We study the exact solution of the Gaudin model with Dzyaloshinsky–Moriya and Kaplan–Shekhtman–Entin–Wohlman–Aharony interactions. The energy and Bethe ansatz equations of the Gaudin model can be obtained via the off-diagonal Bethe ansatz method. Based on the off-diagonal Bethe ansatz solutions, we construct the Bethe states of the inhomogeneous XXX Heisenberg spin chain with the generic open boundaries. By taking a quasi-classical limit, we give explicit closed-form expression of the Bethe states of the Gaudin model. From the numerical simulations for the small-size system, it is shown that some Bethe roots go to infinity when the Gaudin model recovers the U(1) symmetry. Furthermore, it is found that the contribution of those Bethe roots to the Bethe states is a nonzero constant. This fact enables us to recover the Bethe states of the Gaudin model with the U(1) symmetry. These results provide a basis for the further study of the thermodynamic limit, correlation functions, and quantum dynamics of the Gaudin model.

Solubility Determination and Thermodynamic Correlation of Chlorphenesin in 12 Pure Solvents from 288.15 to 328.15 K

The solubility of chlorphenesin (CHP) in 12 solvents was determined by the gravimetric method from 288.15 to 328.15 K under atmospheric pressure. The experimental results were correlated by three t...

Solubility of meloxicam in (Carbitol® + water) mixtures: Determination, correlation, dissolution thermodynamics and preferential solvation

The equilibrium solubility of meloxicam (3) in {Carbitol® (1) + water (2)} mixtures at several temperatures from 293.15 K to 313.15 K has been determined and correlated by means of some well-known thermodynamic correlation models. Solubility increases 1144 times, from x3 = 1.137 × 10−6 in neat water to x3 = 1.300 × 10−3 in neat Carbitol® at 298.15 K. By using the van't Hoff and Gibbs equations the respective apparent thermodynamic quantities of the dissolution and mixing processes, namely Gibbs energy, enthalpy, and entropy, were calculated. Apparent dissolution enthalpies vary from a minimum of 7.7 kJ mol−1 in neat water to a maximum of 32.3 kJ mol−1 in the mixture x1 = 0.10. Moreover, apparent dissolution entropies vary from a minimum of −88.0 J mol−1 K−1 in neat water to a maximum of 9.9 J mol−1 K−1 in the mixture x1 = 0.10. Non-linear enthalpy–entropy relationship was observed for meloxicam in the plot of enthalpy vs. Gibbs energy exhibiting negative slope in the composition region 0.00 < x1 < 0.10 and variant but mainly positive slopes in the other mixtures. Hence, the driving mechanism for meloxicam transfer process from more polar to less polar solvent systems is the entropy in water-rich mixtures and the enthalpy in the other solvent compositions. Furthermore, the preferential solvation of meloxicam by Carbitol® and water was analysed by using the inverse Kirkwood-Buff integrals. Meloxicam is preferentially solvated by water molecules in water-rich mixtures exhibiting a maximum in the mixture x1 = 0.10 with δx1,3 = −3.19 × 10−2 but preferentially solvated by Carbitol® molecules in mixtures 0.12 < x1 < 1.00 exhibiting a maximum in the mixture x1 = 0.20 with δx1,3 = 6.87 × 10−2.

Solubility measurement, thermodynamic correlation and molecular dynamic simulation of naphazoline hydrochloride in four binary solvents

Laser monitoring technique was used for the determination of solid-liquid equilibrium solubility of naphazoline hydrochloride (NPZ) in four binary solvents (methanol + ethanol, methanol + isopropanol, 2-methoxyethanol + isopropanol and methanol + ethyl acetate) at T = (278.15–323.15) K and pressure p = 0.1 MPa. In all cases, solubility of NPZ raised with the increment of temperature. The results also indicated that the addition of positive solvents (methanol or 2-methoxyethanol) on the solution of binary solvent mixtures led to increasing solubility of NPZ in all studied binary solvents. The solute-solvent interaction and solvent-solvent interaction were investigated using radial distribution function (RDF). The RDF results revealed that the change of solvent composition varied as the solute-solvent interplay and solvent-solvent interaction, thereby causing the difference of NPZ solubility. Additionally, the measured data was successfully correlated with the Margules, NRTL and UNIQUAC model to investigate theoretically the solubility of NPZ. Computational results proved that the lower mean values of average relative deviation (100ARD) and root-mean square deviation (104RMSD) were obtained to be (1.675) and (2.338) for calculating the solubility of NPZ in investigated systems, further implying that the UNIQUAC model reflected the most accurate descriptions. Using the experimental solubility data, the changes of thermodynamic properties as enthalpy (ΔmixH and ΔdisH), entropy (ΔmixS and ΔdisS) and Gibbs free energy (ΔmixG and ΔdisG) of mixing and dissolution processes were calculated to investigate the solvation behavior of NPZ in studied systems. It was concluded from positive values of entropy and negative values of Gibbs energy change that the mixing and dissolution processes of NPZ in all studied mixed solvents were entropy-driven and spontaneous.

Chloroquine (antimalaria medication with anti SARS-CoV activity) solubility in supercritical carbon dioxide

Unfortunately, malaria still remains a major problem in tropical areas, and it takes thousands of lives each year and causes millions of infected cases. Besides, on December 2019, a new virus known as coronavirus appeared, that its rapid prevalence caused the World Health Organization (WHO) to consider it a pandemic. As a potential drug for controlling or treating these two undesired diseases at the cellular level, chloroquine and its derivatives are being investigated, although they possess side effects, which must be reduced for effective and safe treatments. With respect to the importance of this medicine, the current research aimed to calculate the solubility of chloroquine in supercritical carbon dioxide, and evaluated effect of pressure and temperature on the solubility. The pressure varied between 120 and 400 bar, and temperatures between 308 and 338 K were set for the measurements. The experimental results revealed that the solubility of chloroquine lies between 1.64 × 10−5 to 8.92 × 10−4 (mole fraction) with different functionality to temperature and pressure. Although the solubility was indicated to be strong function of pressure and temperature, the effect of temperature was more profound and complicated. A crossover pressure point was found in the solubility measurements, which indicated similar behaviour to an inflection point. For the pressures higher than the crossover point, the temperature indicated direct effect on the solubility of chloroquine. On the other hand, for pressures less than the crossover point, temperature enhancement led to a reduction in the solubility of chloroquine. Moreover, the obtained solubility results were correlated via semi-empirical density-based thermodynamic correlations. Five correlations were studied including: Kumar & Johnston, Mendez-Santiago-Teja, Chrastil, Bartle et al., and Garlapati & Madras. The best performance was obtained for Mendez-Santiago-Teja's correlation in terms of average absolute relative deviation percent (12.0%), while the other examined models showed almost the same performance for prediction of chloroquine solubility.

Spectroscopic Study on Aqueous Uranyl(VI) Complexes with Methoxy- and Methylbenzoates: Electronic and Steric Effects of the Substituents

Aqueous complexation of uranyl(VI) ions with methoxy- and methylbenzoates in 0.1 M NaClO4 solutions was studied by means of UV-vis absorption and Raman spectroscopy. The predominance of 1:1 complexation (uranyl to ligand) was verified for all uranyl carboxylates under acidic conditions (-log [H+] < 3.2), and absorption spectra, stability constants, and symmetric stretching frequencies of the uranyl group of the complexes were determined for the first time. For meta- and para-substituted benzoates, a linear free energy relationship (LFER) was observed between the equilibrium constants for the protonation (log βP) and uranyl complexation (log βU) reactions, and the electronic effects of the substituents were successfully described by the Hammett equation. In the case of ortho-substituted benzoates, the stability constant of uranyl 2-methoxybenzoate is slightly lower than the LFER trend, which is generally explained by the destabilization of cross-conjugation in the uranyl complex due to the steric hindrance between the reaction center and adjacent methoxy group. On the contrary, the stability constant of uranyl 2-methylbenzoate is comparable to the LFER trend, implying that the steric effect is relatively insignificant for the smaller methyl group. The utility of such thermodynamic correlations between the uranyl-substituted benzoates is useful for the molecular understanding and predictive modeling of chemical interactions between actinyl(VI) ions and various organic carboxyl groups.

Harnessing Dispersion in Soliton Microcombs to Mitigate Thermal Noise.

We explore intrinsic thermal noise in soliton microcombs, revealing thermodynamic correlations induced by nonlinearity and group-velocity dispersion. A suitable dispersion design gives rise to control over thermal-noise transduction from the environment to a soliton microcomb. We present simulations with the Lugiato-Lefever equation (LLE), including temperature as a stochastic variable. By systematically tuning the dispersion, we suppress repetition-rate frequency fluctuations by up to 50 decibels for different LLE soliton solutions. In an experiment, we observe a measurement-system-limited 15-decibel reduction in the repetition-rate phase noise for various settings of the pump-laser frequency, and our measurements agree with a thermal-noise model. Finally, we compare two octave-spanning soliton microcombs with similar optical spectra and offset frequencies, but with designed differences in dispersion. Remarkably, their thermal-noise-limited carrier-envelope-offset frequency linewidths are 1MHz and 100Hz, which demonstrates an unprecedented potential to mitigate thermal noise. Our results guide future soliton-microcomb design for low-noise applications, and, more generally, they illuminate emergent properties of nonlinear, multimode optical systems subject to intrinsic fluctuations.

Adsorption of ciprofloxacin to functionalized nano-sized polystyrene plastic: Kinetics, thermochemistry and toxicity

Plastic debris is ubiquitous in aquatic systems and has been proven vehicles for the transport of various pollutants including trace organic compounds. Nanoplastics have large specific surface area and hydrophobic characteristics and therefore are capable of adsorbing other organic or inorganic chemicals from the environment. Antibiotics, as another class of emerging contaminants, have raised significant research concern in recent years as they pose threats to the ecosytems and human health. Nevertheless, little information is available on the adsorption behaviors of antibiotics onto nano-sized plastics. The toxicity of combined nanoplastics and antibiotics is also largely unknown. In this study, the physicochemical and thermodynamic interactions between representative nanoplastics, which containing a carboxyl functional group of polystyrene nanoplastics (PS-COOH), and typical antibiotic, i.e., ciprofloxacin (CIP) were investigated in a batch adsorption experiment. The specific thermodynamic correlation function of PS-COOH combined with CIP was obtained through isothermal titration microcalorimetry (ITC) analysis. The adsorption kinetics and isotherm of CIP on PS-COOH closely fit the pseudo-second-order kinetic model (r2 = 0.99) and Freundlich isotherm (r2 = 0.99). The ITC results showed that the adsorption reaction of PS-COOH with CIP was a spontaneous exothermic reaction. The adsorption of antibiotics on nanoplastics may aggravate the negative impacts of these two pollutants on aqueous ecosystems, and we hypothesized that would be reflected in the survival rate of model organism of Caenorhabditis elegans when exposed to this combination. This work used a mechanistic approach to unravel the adsorption behavior of antibiotics on nanoplastics and shed light on their potential impact on aquatic ecosystems.

Thermodynamic modeling and correlations of CH4, C2H6, CO2, H2S, and N2 hydrates with cage occupancies

The present work focuses on developing a framework for accurate prediction of thermodynamic conditions for single-component hydrates, namely CH4, CO2, N2, H2S, and C2H6 (coded in MATLAB). For this purpose, an exhaustive approach is adopted by incorporating eight different equations of states, namely Peng–Robinson, van der Waals, Soave–Redlich–Kwong, Virial, Redlich–Kwong, Tsai-Teja, Patel, and Esmaeilzadeh–Roshanfekr, with the well-known van der Waals–Platteeuw model. Overall, for I–H–V phase region, the Virial and van der Waals equation of state gives the most accurate predictions with minimum AAD%. For Lw–H–V phase region, Peng–Robinson equation of state is found to yield the most accurate predictions with overall AAD of 3.36%. Also, genetic programming algorithm is adopted to develop a generalized correlation. Overall, the correlation yields quick estimation with an average deviation of less than 1%. The accurate estimation yields a minimal AAD of 0.32% for CH4, 1.93% for C2H6, 0.77% for CO2, 0.64% for H2S, and 0.72% for N2. The same correlation can be employed for fitting phase equilibrium data for other hydrates too. The tuning parameter, n, is to be used for fine adjustment to the phase equilibrium data. The findings of this study can help for a better understanding of phase equilibrium and cage occupancy behavior of different gas hydrates. The accuracy in phase equilibria is intimately related to industrial applications such as crude oil transportation, solid separation, and gas storage. To date, no single correlation is available in the literature that can accurately predict phase equilibria for multiple hydrate species. The novelty of the present work lies in both the accuracy and generalizability of the proposed correlation in predicting the phase equilibrium data. The genetic programming generalized correlation is convenient for performing quick equilibrium prediction for industrial applications.

Solubility measurement, thermodynamic correlation and molecular simulations of uracil in (alcohol + water) binary solvents at (283.15–318.15) K

The solubility of uracil in binary solvent mixtures, including (methanol + water), (ethanol + water) and (isopropanol + water), was determined from 283.15 K to 318.15 K by the ultraviolet spectroscopic method. It was shown by experiments that when the composition of solvent is constant, the solubility of uracil increases with the temperature. And the solubility of uracil in the binary solvent mixtures ranges as: (isopropanol + water) > (ethanol + water) > (methanol + water). Under isothermal conditions, as the mole fraction of organic solvent increases, the solubility of uracil increases first and then decreases gradually. To further verify the observed phenomena, the molecular simulations, including molecular electrostatic potential surface, Hirshfeld surface analysis and solvation free energy were provided. Besides, the modified Apelblat equation, λh model, CNIBS/R-K model, Jouyban-Acree model and NRTL model, were selected to correlate the experimental data, respectively. The results indicated that all selected thermodynamic models have good accuracy. Furthermore, the standard thermodynamic properties of the mixtures, including Gibbs energy, entropy and enthalpy were calculated and discussed, which indicated that the dissolution of the uracil in these three binary solvent mixtures is spontaneous and endothermic. All the results presented in this paper have some reference value to the further study of uracil.

Thermal Conductivities of Choline Chloride-Based Deep Eutectic Solvents and Their Mixtures with Water: Measurement and Estimation.

The thermal conductivities of selected deep eutectic solvents (DESs) were determined using the modified transient plane source (MTPS) method over the temperature range from 295 K to 363 K at atmospheric pressure. The results were found to range from 0.198 W·m−1·K−1 to 0.250 W·m−1·K−1. Various empirical and thermodynamic correlations present in literature, including the group contribution method and mixing correlations, were used to model the thermal conductivities of these DES at different temperatures. The predictions of these correlations were compared and consolidated with the reported experimental values. In addition, the thermal conductivities of DES mixtures with water over a wide range of compositions at 298 K and atmospheric pressure were measured. The standard uncertainty in thermal conductivity was estimated to be less than ± 0.001 W·m−1·K−1 and ± 0.05 K in temperature. The results indicated that DES have significant potential for use as heat transfer fluids.

Unraveling thermodynamic and conformational correlations in action of osmolytes on hen egg white lysozyme

The effect of glycine, L-alanine, DL-α-aminobutyric acid, in combination with each other and with a sugar alcohol sorbitol has been examined on the globular protein hen egg-white lysozyme.The objective of the work is to examine if synergy operates in these systems and to understand if sorbitol which has several hydroxyl groups can alter the effect of osmolytes on protein. A combination of uv-visible, fluorescence, circular dichroism spectroscopies, and high sensitivity isothermal titration calorimetry have been employed to address the changes in thermal stability and conformation of the protein in the presence of mixture of these osmolytes. The values of heats of interaction of the protein with mixture of osmolytes and those of interaction of one osmolyte with the other have been determined in arriving at the proposed mode of action. Thermodynamic signatures of interaction between the osmolytes have been correlated with transition temperature and conformation of the protein to unravel the mode of action in defining extent or occurrence of synergy in these systems. Further, the results have been interpreted to obtain experimental evidence for the proposed mode of action which suggests absence of appreciable interaction among these osmolytes in mixture and occurrence of individual action in preferential hydration of the protein.

Solubility measurement and thermodynamic model correlation of propyl gallate in pure and binary solvents from T = (293.15 to 333.15) K

The solid−liquid equilibrium data of propyl gallate in nine pure solvents and binary solvent mixtures of ethanol + n-propanol were measured over the temperature range from (293.15 to 333.15) K by using a gravimetric method under atmospheric pressure. The experimental result proved that the rising temperature led to increased solubility of the propyl gallate in all selected solvents. For pure solvents, the solubility of propyl gallate increased according to the following order: ethanol < isobutanol < ethyl acetate < methanol < n-butanol < methyl acetate < isopropanol < n-propanol < acetone. For ethanol + n-propanol mixture solvents, the solubility of propyl gallate decreased with the increase of ethanol mass fraction. The experimental solubility in each selected solvent were correlated with a series of equations, including the modified Apelblat equation, Van't Hoff equation, λh equation, NRTL equation and Wilson equation. Computational results showed that all five selected models well fitted the experimental data. Hansen solubility parameters (HSP) were also applied to explain the solubility behavior of propyl gallate. In addition, the Van't Hoff equation was used to estimate the dissolution enthalpy (∆H°sol), dissolution entropy (∆S°sol) and Gibbs energy (ΔG°sol) of propyl gallate in selected solvents.

Vapor–Liquid Equilibrium Measurement and Thermodynamic Correlations of 4-Nonyl Phenol Diethoxylate with sec-Butanol at Elevated Pressures

The isothermal vapor–liquid equilibrium (VLE) data for a binary system of 4-nonyl phenol diethoxylate with sec-butanol at (333.0 to 425.0) K have been measured by using a static-type apparatus. The system pressures at a given feed composition were measured to generate the P–T–x data and are further compared to the pressure values calculated using the Antoine equation. Two thermodynamic models, the UNIQUAC and the NRTL models, were selected to correlate the VLE data at various temperatures. The analysis showed that the experimental data agree well with these activity coefficient models. Finally, the solvent activities were estimated, and the values are consistent with the values calculated from the phase equilibrium data.