Calculation Of Thermodynamic Parameters Research Articles

ION-EXCHANGE SORPTION OF SOME METAL IONS ON CLINOPOTHYLOLITE FROM WATER SOLUTIONS AND SOILS. THEORETICAL CALCULATIONS AND EXPERIMENTAL STUDIES

The sorption of the lead, cadmium and copper cations in static conditions on the rock of clinoptilolite of the Sokyrnitsa deposit (Transcarpathian region,Ukraine) has been investigated using the conventional complexonometric analytical technique as well as quantum chemical calculations. The samples of сlinoptilolite were previously transferred to sodium form, treated with 1M sodium chloride solution for 8 hours at a temperature of 90 degrees Celsius. The grain size of clinoptilolite was 2-3 mm. For the study of sorption, a series of solutions of nitrates of the corresponding metals have been used; the initial concentration of solutions was 0.02 mol / liter. The mass ratio between clinoptilolite and solution was 1:20.Sorption was investigated in the presence of salicylic acid, which has been employed in order to model the behavior of various fulvic acids in the soils. In parallel, the quantum-chemical calculations, in order to check the possibility of sorption of lead, cadmium and copper ions in the presence of salicylic acid, have been carried out. For the above calculations, a fragment of clinoptilolite with an aluminum atom in the T1 position was used, whereas sodium cation has been used as an anti-cation. Optimization of geometry and calculation of thermodynamic parameters were carried out using the PBE/3ζ level method using the software PRIRODA.The results of the calculations of the exchange reaction (1) show the possibility of its spontaneous flow (the negative value of the change of Gibbs energy) for all the considered metals (lead, cadmium and copper).Clin-Na(H2O)3 + (Sal)2Ме(H2O)n + (12-n)H2O→ Clin-Me(H2O)3 + 2(Sal–)(H2O)3 + Na(H2O)6 (1)The presence of salicylic acid leads to a decrease of the sorption ability, but even the 1 : 2 ratio of Me2+ : salicylic acid can reduce the concentration of metal by 70% for cadmium, 48% for copper and 42% for lead.Thermodynamic calculations have been confirmed experimentally, and can readily be used in further investigations on the decontamination, by using clinoptilolite and other inorganic and mineral sorbents, of the soils contaminated and/or polluted with the heavy metal ions.

Adsorption of Fe(II) Ions from Aqueous Solution Using Silica-Supported Organic–Inorganic Hybrid Sorbents

A silica-supported organic–inorganic hybrid sorbents were prepared by sol–gel method and characterized by Fourier transmission infrared spectroscopy, scanning electron microscopy with energy dispersive spectrometry and thermal analysis. The adsorption behaviors of Fe(II) ions onto the hybrid sorbents from aqueous media had been investigated. The adsorption capacity of hybrid sorbents for Fe(II) ions was 90.7 mg g−1. Adsorption equilibrium of Fe(II) ions was achieved within 30 min of contact time. Solution pH had a minor effect on Fe(II) ions adsorption in the range of pH 3–6. The highly selective binding of the hybrid sorbents for Fe(II) ions with respective to other competitor ions (such as Cd(II), Zn(II), Co(II), Ni(II), and Pb(II) ions) was due to the high complexation affinity between Fe(II) ions and cyano groups. The adsorption/desorption cycle of hybrid sorbent could be up to three times. Experimental data revealed that Langmuir isotherm and pseudo–second–order models give best fit for Fe(II) ions adsorption with high correlation coefficients (>0.99). The calculation of thermodynamic parameters showed that the adsorption of Fe(II) ions on the hybrid sorbents was an exothermic and spontaneous process. These results confirmed that the hybrid sorbent could be a potential sorbent for the removal of Fe(II) ions from aqueous solutions.

Phonon stability, electronic structure results, mechanical and thermodynamic properties of RbSbO3 and CsSbO3 perovskite oxides: Ab initio investigation

Cubic perovskite oxides RbSbO3 and CsSbO3 have been investigated for structural stability, electronic results, elastic, mechanical stability and thermodynamic results by most accurate density functional theory (DFT). The optimization has been completed using Local density approximation (LDA) and Generalized gradient approximation (GGA) within the scheme of Perdew, Burke and Ernzrhof (PBE). The ground state optimized results present minimum energy within GGA for both compounds. Band structure and density of state results both present the metallic nature for these compounds. The mechanical properties like Young's modulus, Bulk modulus etc. have been deduced from elastic values. RbSbO3 was found to have more resistance to compression as compared to strength CsSbO3. Both the materials were found to have brittle nature from Poisson's ratio (υ), Cauchy's pressure (C12–C44) and Pugh ratio (B/G) criteria. The melting temperature was calculated to be 2148 ± 300 K, 1746 ± 300 K, respectively for RbSbO3 and CsSbO3. Pressure and temperature variation has been used for calculation of thermodynamic parameters within quasi-harmonic Debye approximation. The nature of Bulk modulus, cell volume, specific heat capacity and thermal expansion has been computed in the temperature range of 0 K–900 K and pressure varied from 0 GPa to 15 GPa.

Calculations of Thermodynamic Parameters of Charged Microparticle Structures in Electrodynamic Traps

Calculations of Thermodynamic Parameters of Charged Microparticle Structures in Electrodynamic Traps

Comparative effect of ionic liquids pretreatment on thermogravimetric kinetics of crude oil palm biomass for possible sustainable exploitation

Crude oil palm biomass (OPB) residue is an important source of lignocellulose and could be transformed into biofuels through thermochemical conversion for heat and power in CHP plants or act as sustainable reinforcement in the biocomposite industry. Effective pretreatment is an essential task for the utilization of waste biomass for bioenergy and biomaterials. The comparative effect of two ionic liquids (ILs), 1-butyl-3-methylimidazolium chloride ([bmim][Cl]) and 1-ethyl-3-methylimidazolium diethylphosphate ([emim[dep]), on OPB pyrolysis kinetic and thermodynamic parameters was studied using thermogravimetric analysis (TGA) coupled with Coats-Redfern integral method. The OPB residue was pretreated with ILs [bmim][Cl] and [emim][dep] under mild processing conditions of 90 °C for 3 h and was also subjected to three other conventional pretreatment methods called dilute acid, alkaline, and hot compressed water to better understand and compare the performance of ILs for pretreatment of lignocellulosic OPB. Results reveal that ILs pretreatment was superior in terms of delignification of OPB and produced the cellulose-rich fiber with 48.2% and 41.2% cellulose compared to cellulose fraction of 26.4% for the untreated sample. The values of apparent activation energies were found to be 81.8, 90.9, 92.0, 84.9, 83.8, and 93.5 kJ/mol for untreated, [bmim][Cl], [emim][dep], dilute acid, base, and hot compressed water pretreatments respectively. Further calculation of thermodynamic parameters led to the change in Gibb's free energy (ΔG°) values of 188.9, 208.0, 210.9, 219.1, 217.4 and 217.1, kJ/mol for untreated, [bmim][Cl], [emim][dep], dilute acid, base, and hot compressed water pretreatments respectively. The higher change in entropy (ΔS°) values of ILs-pretreated fibers compared to the untreated one showed that dissolution and regeneration from ILs solution had unlocked the complex 3D structure of lignocellulose, resulting in increased disorder. The results plainly revealed that ILs-based pretreatment could be a promising and environmentally benign technology for efficient utilization of agricultural residues in the fields of biofuels and biocomposite materials.

Response to “Some remarks on a critical review of the estimation of the thermodynamic parameters on adsorption equilibria. Wrong use of equilibrium constant in the van't Hoff equation for calculation of thermodynamic parameters of adsorption - Journal of Molecular Liquids 273 (2019) 425–434.”

• The response to the letter to the editor • Determination of thermodynamic parameters by using the van't Hoff equation. • Use of nonlinear equilibrium isotherms at several temperatures to obtain the K.

Diverse Effects of Different "Protein-Based" Vehicles on the Stability and Bioavailability of Curcumin: Spectroscopic Evaluation of the Antioxidant Activity and Cytotoxicity In Vitro.

Background:Curcumin is a natural polyphenolic compound with anti-cancer, anti-inflammatory, and anti-oxidation properties. Low water solubility and rapid hydrolyt-ic degradation are two challenges limiting use of curcumin.Objective:In this study, the roles of the native/modified forms of Bovine Serum Albumin (BSA), β-lactoglobulin (β-lg) and casein, as food-grade biopolymers and also protein chemical modification, in stabilizing and on biological activity of curcumin were sur-veyed.Methods:In this article, we used various spectroscopic as well as cell culture-based tech-niques along with calculation of thermodynamic parameters.Results:Investigation of curcumin stability indicated that curcumin binding to the native BSA and modified β-lg were stronger than those of the modified BSA and native β-lg, respectively and hence, the native BSA and modified β-lg could suppress water-mediated and light-mediated curcumin degradation, significantly. Moreover, in the presence of the native proteins (BSA and casein), curcumin revealed elevated in vitro anti-cancer activity against MCF-7 (human breast carcinoma cell line) and SKNMC (human neuroblastoma cell line). As well, curcumin, in the presence of the unmodified “BSA and β-lg”, was more potent to decrease ROS generation by hydrogen peroxide (H2O2) whereas it led to an inverse outcome in the presence of native casein. Overall, in the presence of the pro-tein-bound curcumin, increased anti-cancer activity and decreased ROS generation by H2O2 in vitro were documented.Conclusion:It appears that “water exclusion” is major determinant factor for increased stability/efficacy of the bound curcumin so that some protein-curcumin systems may pro-vide novel tools to increase both food quality and the bioavailability of curcumin as health promoting agent.

The phase selection via machine learning in high entropy alloys

The phase formation of high entropy alloys (HEAs) is diversity due to the breadth of the composition space. Most of the studies about phase formation are based on features of solid solution. However, the establishment of the link between compositions and phase formation plays an important role in accelerating novel HEAs development. To achieve this aim, we employed the support vector machine (SVM) to build phase selection models with both the composition dataset and the thermodynamic parameters dataset. The accuracies of both models are above 85%. A dataset with more than a thousand data has been established, which covers 18 elements and most of the HEAs families. The feature dataset was transferred by calculation of thermodynamic parameters. The similar accuracies of the models with compositions dataset and with thermodynamic parameters proved that the prediction of phase formation in HEAs can be carried out directly from compositions. Our models provide a universal approach of phase formation prediction in HEAs.

On one Method of Calculating Moving Boundaries in Euler Coordinates

The paper presents a method for calculating a moving boundary in Euler coordinates as an application to studies of gas flows in areas with an impermeable wall. The method is based on a combination of the Eulerian grid and one Lagrangian border cell formed by the combination of two cells adjacent directly to the moving border. Reconstruction of the entire computational domain is not required. This fact has a significant impact on the computational performance. We describe the algorithm for combination of cells, present the calculation of thermodynamic parameters, and justify the expression for the internal energy of the combined interval. The method was verified using an analytical solution to the problem of a converging shock wave in a vessel with an impermeable wall. Finally, we compare the entropy functions of the analytical and numerical solutions.

Equation of state for aluminum in warm dense matter regime**Project supported by the National Natural Science Foundation of China (Grant No. 51807050), the National Basic Research Program of China (Grant No. 2015CB251002) and the Program for the Top Young and Middle-aged Innovative Talents of Higher Learning Institutions of Hebei, China (Grant No. BJ2017038).

A semi-empirical equation of state model for aluminum in a warm dense matter regime is constructed. The equation of state, which is subdivided into a cold term, thermal contributions of ions and electrons, covers a broad range of phase diagram from solid state to plasma state. The cold term and thermal contribution of ions are from the Bushman–Lomonosov model, in which several undetermined parameters are fitted based on equation of state theories and specific experimental data. The Thomas–Fermi–Kirzhnits model is employed to estimate the thermal contribution of electrons. Some practical modifications are introduced to the Thomas–Fermi–Kirzhnits model to improve the prediction of the equation of state model. Theoretical calculation of thermodynamic parameters, including phase diagram, curves of isothermal compression at ambient temperature, melting, and Hugoniot, are analyzed and compared with relevant experimental data and other theoretical evaluations.

Some remarks on “A critical review of the estimation of the thermodynamic parameters on adsorption equilibria. Wrong use of equilibrium constant in the Van't Hoof equation for calculation of thermodynamic parameters of adsorption” - Journal of Molecular Liquids 273 (2019) 425–434

Some remarks on “A critical review of the estimation of the thermodynamic parameters on adsorption equilibria. Wrong use of equilibrium constant in the Van't Hoof equation for calculation of thermodynamic parameters of adsorption” - Journal of Molecular Liquids 273 (2019) 425–434

Mixed micellization and surface properties of non-ionic/cationic surfactants

We investigate the surface properties of aqueous binary mixtures of our cationic surfactant O-dodecyl-N,N′-diisopropylisourea hydrochloride (ISO-DIC C12) with commercially available nonionic surfactant polyoxyethylene p-(1,1,3,3-tetramethylbutyl)phenyl ether (TritonX-100) at different temperatures (288 to 303 K). The micellization behavior of the binary systems is studied by determining the surface tension and other important physicochemical parameters, such as the critical micelle concentration (CMC), surface tension at the CMC(γcmc), Krafft Temperature (TK), maximum excess concentration (Γmax), minimum surface area per molecule (Amin), surface pressure at the CMC (Пcmc), and the adsorption efficiency (pC20) at the air/water interface. The study has additionally covered the calculation of thermodynamic parameters of micellization, including the standard Gibbs free energy, the standard enthalpy, the standard entropy, the free energy, and the Gibbs free energy of adsorption at air/water interface. The CMC values of the binary systems determined by experimental data are used to evaluate the micellar composition in the mixed micelle, the interaction parameter β and the activity coefficients f1(ISO-DIC C12) and f2 (polyoxyethylene p-(1,1,3,3-tetramethylbutyl)phenyl ether) using the theoretical treatment proposed by Clint and Rubingh. Our results reveal that the proposed binary systems possess enhanced surface activity compared to those of the individual surfactants.

Removal of U (VI) from acidic and alkaline aqueous solutions by zero-valent iron nanoparticles

Removal of uranium (VI) from aqueous solutions by zero-valent iron nanoparticles (nZVI) was investigated in both acidic and alkaline solutions in absence and presence of counter-ions (0.1 M NaNO3). Langmuir and Freundlich equations were applied to model the sorption isotherms whereas the data obtained at 15, 25, 35 and 45 °C from the kinetic experiments were successfully reproduced by a pseudo-second order equation and used for calculation of thermodynamic parameters. Electron microscopy (SEM/EDS), X-ray photoelectron spectroscopy and UV-Fluorescence were applied to explore possible mechanisms. The U-removal seems to be due mainly to sorption followed by U(VI) reduction.

A critical review of the estimation of the thermodynamic parameters on adsorption equilibria. Wrong use of equilibrium constant in the Van't Hoof equation for calculation of thermodynamic parameters of adsorption

In the adsorption literature, the Van't Hoff equation is used in different manners without any criteria about the concepts of physical-chemistry of equilibrium for calculation of thermodynamic parameters of adsorption. Indeed, the equilibrium constant (K) should be dimensionless for being used in the Van't Hoff equation. However, this is not a simple adjustment of units, as being spread in the literature, to become K dimensionless. In this paper, it will be calculated the equilibrium constants using numeric examples and show the flaws of the thermodynamics calculations, when the value of K is wrongly calculated, and what are the expected results of the changes in enthalpy (ΔH°) and changes in the entropy (ΔS°) that are spread in the literature.

Enhanced Adsorption of Zn(II) onto Graphene Oxides Investigated Using Batch and Modeling Techniques.

Graphene oxide (GO) was synthesized and employed as an adsorbent for Zn(II) removal from an aqueous solution. The adsorption isotherms showed that Zn(II) adsorption can be better described using the Freundlich model than the Langmuir model. The maximum adsorption capacity of Zn(II) on GO determined using the Langmuir model at pH 7.0 and 293 K was 208.33 mg/g. The calculation of thermodynamic parameters revealed that the process of Zn(II) adsorption on GO was chemisorptions, endothermic, and spontaneous. Kinetic studies indicated that the pseudo-second-order kinetic model showed a better simulation of Zn(II) adsorption than the pseudo-first-order kinetic model. On the basis of surface complexation modeling, the double layer model provided a satisfactory prediction of Zn(II) by inner-sphere surface complexes (for example, SOZn+ and SOZnOH species), indicating that the interaction mechanism between Zn(II) and GO was mainly inner-sphere complexation. In terms of reusability, GO could maintain 92.23% of its initial capability after six cycles. These findings indicated that GO was a promising candidate for the immobilization and preconcentration of Zn(II) from aqueous solutions.

Re-evaluation of the century-old Langmuir isotherm for modeling adsorption phenomena in solution

One of the first reported equations to describe adsorption at equilibrium is the Langmuir model (J. Am. Chem. Soc. 1918, 40, 1361–1403). Initially, the model was used to describe adsorption from the gas phase, along with adsorption from the liquid phase. Herein, the shortcomings of the Langmuir model for adsorption processes from liquid phase are revealed. This study reports a revised form of the Langmuir isotherm model that provides further insight on the nature of adsorption and desorption processes in condensed phases. This approach is anticipated to provide a theoretical background for universal calculation of the adsorption thermodynamic parameters. We also provide an overview of the methods that use the Langmuir equilibrium constant for calculation of thermodynamic parameters of adsorption and source of their limitations are highlighted.

Comparative Study of Toluidine Blue O and Methylene Blue Binding to Lysozyme and Their Inhibitory Effects on Protein Aggregation.

A comparative binding interaction of toluidine blue O (TBO) and methylene blue (MB) with lysozyme was investigated by multifaceted biophysical approaches as well as from the aspects of in silico biophysics. The bindings were static, and it occurred via ground-state complex formation as confirmed from time-resolved fluorescence experiments. From steady-state fluorescence and anisotropy, binding constants were calculated, and it was found that TBO binds more effectively than MB. Synchronous fluorescence spectra revealed that binding of dyes to lysozyme causes polarity changes around the tryptophan (Trp) moiety, most likely at Trp 62 and 63. Calorimetric titration also depicts the higher binding affinity of TBO over MB, and the interactions were exothermic and entropy-driven. In silico studies revealed the potential binding pockets in lysozyme and the participation of residues Trp 62 and 63 in ligand binding. Furthermore, calculations of thermodynamic parameters from the theoretical docking studies were in compliance with experimental observations. Moreover, an inhibitory effect of these dyes to lysozyme fibrillogenesis was examined, and the morphology of the formed fibril was scanned by atomic force microscopy imaging. TBO was observed to exhibit higher potential in inhibiting the fibrillogenesis than MB, and this phenomenon stands out as a promising antiamyloid therapeutic strategy.

Sorption of Heavy Metal Ions from Water by Natural Apatite Ore

The article shows the efficient use of natural apatite ore in purification of mining industrial wastewaters from heavy metal ions. The determination of adsorption constants, calculation of thermodynamic parameters at various pH of the medium were carried out. It was established that the sorbent based on apatite ore may be used in ecological and technological aims in water conditioning and water treatment.

Synergistic effect of Cu(II) in the one-pot synthesis of reduced graphene oxide (rGO/CuxO) nanohybrids as adsorbents for cationic and anionic dyes

The present work considered the effects of Cu(II) loadings on the shape and size of CuxO nanoparticles, (where, x = 1, 2), blended with reduced graphene oxide through the one-pot hydrothermal procedure to get rGO/CuxO nanohybrids. These nanohybrids are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infra-red (FT-IR), and thermogravimetric analysis (TGA) techniques. The formation of spherical and monoclinic Cu2O are well detected at lower Cu(II) loadings and higher NaOH concentrations, while at the highest Cu(II) loading and lower NaOH concentrations the CuO nanorods clearly observed. The nanohybrids have been utilized as adsorbents for the removal of Methyl blue (MB) and Crystal violet (CV) as models of anionic and cationic dyes, respectively. The maximum removal of MB within 20 min occurs at optimized pH = 6, while for CV the alkaline medium is desired. The adsorption data well fitted using the pseudo-second-order kinetics, whilst the adsorption isotherms best represented by the Langmuir isotherm model. The adsorption capacity with qmax = 1200 mg g−1 of MB for the nanohybrid with lowest Cu(II) loadings, rGO/Cu2O, was higher than that of CV (qmax = 238.6 mg g−1), signifying the higher perspective for anionic dye removal. Therefore, this sturdy affinity of MB comparing with CV on rGO/Cu2O is mainly due to the high degree of the aromaticity of MB and the π-π interactions with rGO nanosheets. Furthermore, the calculation of thermodynamic parameters verified the feasibility of adsorption process. Moreover, the adsorbents recovered effectively by promising recovery method and reused.

Synthesis of dipolar grafted hydroxyethyl cellulose and its application for the removal of phosphate ion from aqueous medium by adsorption

A novel amphoteric graft copolymer was prepared by first grafting of a cationic monomer, (3-Acrylamidopropyl) trimethyl-ammonium chloride (APTAC) using potassium peroxydisulfate (K2S2O8) as radical initiator, followed by sulfation with chlorosulfonic acid as sulfating agent onto hydroxyethyl cellulosic (HEC) backbone. Several techniques like FTIR, 1H NMR, FESEM, XRD and TGA/DTGA studies were used to characterize the graft copolymer. The dipolar graft copolymer, sulfated hydroxyethyl cellulose-g-polyAPTAC (SHEC-g-PAPTAC) so obtained was used for phosphate ion adsorption from water medium. Various operating variables affecting the phosphate adsorption were studied which showed that the maximum phosphate adsorption was obtained at pH 5, time 45 min, temperature 50 °C, adsorbent dose 0.02 g and initial phosphate ion concentration 120 mg/L. Adsorption mechanism was theoretically interpreted by Density Functional Theory (DFT), using Gaussian 09 software which supports the experimentally obtained data. The adsorption follows pseudo-second-order kinetic and Langmuir isotherm model with Qmax value 46.94 mg/g. Calculation of thermodynamic parameters (negative value of Gibbs free energy change (ΔG°)) indicates the spontaneous nature of the adsorption. Adsorption capacities of both hydroxyethyl cellulose-g-polyAPTAC (HEC-g-PAPTAC) and SHEC-g-PAPTAC copolymer were also compared under optimum conditions. Desorption study showed that the sulfated polymer was retained almost 86% regeneration efficiency after four adsorption-desorption cycles.