Enthalpy Research Papers - Academia.edu (original) (raw)

This work shows the experimental data of excess properties at several temperatures and the vapor–liquid equilibria (VLE) obtained for four binary systems of alkyl methanoates (methyl to butyl) with decane, all measured at constant pressure of 101.32kPa. The isobaric VLE data were thermodynamically consistent according to the Fredenslund test and did not present an azeotrope. The experimental data of HmE

- by
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- Chemical Engineering, Thermodynamics, VLE, Classical Physics

Talc samples in both sheet and powder form are studied by adsorption calorimetry and adsorption isotherm techniques. A model is used to determine the solid surface energy, the solid surface tension and the dispersive, acidic, and basic components of these terms. These results are introduced in an approximate equation relating adsorption to contact angle data. Experimental contact angles are in correct agreement with this approach. The Neumann equation of state is used to fit the data and discussed. It appears as a numerical form of the general equation taking into account gas adsorption and film pressure. Behaviors of talc in contact with liquids do not appear very different whether the solid is in sheet or powder form. C 2002 Elsevier Science (USA)

- by Harold Malandrini
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- Engineering, Modeling, Immersion, Enthalpy

The moisture accumulation within clothing is a serious problem for sportswear and clothing in cold climate. There are several experimental methods available to measure moisture build up in insulate materials. However, information on parameters such as temperature, relative humidity and vapor pressure can be obtained through simulation using a predictive mathematical model. The focus of this study is the development of a mathematical model to simulate heat and moisture transfer in a sample of fabric, coated to provide insulation, which is in contact with human skin on one side and with the external environment on the other. To numerically simulate the mathematical model the finite volume method is used and a computational procedure for the solution of the model is designed. The simulation results are analyzed to verify whether they are consistent with the physical reality.

- by Selene Guelli Souza
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- Engineering, Applied Mathematics, Dentistry, Biomedical Engineering

Aims: The present investigation deals with the development of thermotolerant mutant strain of yeast for studying enhanced productivity of ethanol from molasses in a fully controlled bioreactor. Methods and Results: The parental culture of Saccharomyces cerevisiae ATCC 26602 was mutated using UV treatment. A single thermotolerant mutant was isolated after extensive screening and optimization, and grown on molasses medium in liquid cultures. The mutant was 1AE45-fold improved than its wild parent with respect to ethanol productivity (7AE2 g l )1 h )1 ), product yield (0AE44 g ethanol g )1 substrate utilized) and specific ethanol yield (19AE0 g ethanol g )1 cells). The improved ethanol productivity was directly correlated with titres of intracellular and extracellular invertase activities. The mutant supported higher volumetric and product yield of ethanol, significantly (P £ 0AE05) higher than the parental and other strains. The mutated cultures produced 1AE8-and 2AE6-fold more extracellular and intracellular invertase productivity, respectively, than that produced by its wild parent at 40°C. Thermodynamic studies revealed that the cell system exerted protection against thermal inactivation during formation of products. Conclusions: A mutant derivative of Sacchromyces cerevisiae with improved productivity of ethanol and invertases has been obtained, which showed concomitant improvement in thermostability of endogenous metabolism for formation of both ethanol and invertases. Significance and Impact of the Study: The results of the present study are of commercial value as the mutant can be used for ethanol production in parts of Pakistan where the temperature may go up to 40°C in April. Ethanol product yield coefficient and volumetric productivity, revealed the hyper-productivity of ethanol from molasses at 40°C, which is not appropriate for wild organism.

- by Muhammad Ferhan
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- Thermodynamics, Kinetics, Multidisciplinary, Entropy

In recent years our group has performed a thorough study of the dense region of the phase diagram of water. In this paper we report the numerical results for the triple points and for the change in volume, Dv, and enthalpy, DH, along the coexistence lines involving liquid water and/or ices ih (hexagonal), II, III, V and VI for several simple water models. The predictions for Dv using the TIP4P/2005 model are in excellent agreement with the experimental values. As to DH for the same model, the computer simulation results are also satisfactory although there are small but significant differences between simulation and experiment.

- by carlos vega
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- Water, Prediction, Models, Enthalpy

The solubility of CO 2 in six pyridinium based ionic liquids 1-butylpyridinium bis(trifluoromethylsulfonyl)imide [C 4 py][Tf 2 N], 1-octylpyridinium bis(trifluoromethylsulfonyl)imide [C 8 py][Tf 2 N], 1-decylpyridinium bis(trifluoromethylsulfonyl)imide [C 10 py][Tf 2 N], 1-dodecylpyridinium bis(trifluoromethylsulfonyl)imide [C 12 py][Tf 2 N], 1-butylpyridinium trifluoroacetate [C 4 py][TfAc] and 1-butylpyridinium dicyanamide [C 4 py][Dca] was measured at temperatures of 298.15 K, 313.15 K and 333.15 K and in the pressure range from 0.25 bar to 10 bar. The results showed that the solubility of CO 2 increase with increasing pressure and decrease with increasing temperature. The solubility of CO 2 in this six ionic liquids at 298.15 K was in the sequence of [C 12 py][Tf 2 N] > [C 10 py][Tf 2 N] > [C 8 py][Tf 2 N] > [C 4 py][Tf 2 N] > [C 4 py][TfAc] > [C 4 py][Dca]. The Henry's law constants, partial molar enthalpy and partial molar entropy of dissolution of CO 2 gas in these ionic liquids, were also estimated. The regeneration and recyclability studies of [C 4 py][Tf 2 N] proved their thermal and physical stability for commercial applications.

- by Mohamad A Z M I Bustam
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- Chemical Engineering, Entropy, Enthalpy, Solubility

The present paper is aimed to investigate and develop cheap adsorption methods for colour removal from wastewater using waste material de-oiled mustard as adsorbent. De-oiled mustard, a biosorbent, was successfully utilized for removing a water-soluble xanthene dye, Erythrosine from wastewater. Kinetic studies of adsorption of Erythrosine at de-oiled mustard were carried out at 30 • C, using aqueous solutions with 5 × 10 −5 M concentration of Erythrosine. The adsorption process followed a pseudo-first order model. The equilibrium process can be well described by both Freundlich and Langmuir models, at 30, 40 and 50 • C. Free energy of adsorption (G •), enthalpy (H •), and entropy (S •) changes were calculated to predict the nature of adsorption. The estimated values for G • were −12.81 × 10 3 and −12.57 × 10 3 over activated carbon and activated de-oiled mustard at 203 K (30 • C), indicate toward a spontaneous process. The positive value for H • indicates that the adsorption of Erythrosine dye to de-oiled mustard is an endothermic process.

- by Rajeev Jain
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- Engineering, Thermodynamics, Kinetics, Modeling

Haloperidol (Hal), a highly hydrophobic drug, was complexed with two i-cyclodextrin (i-CD) derivatives. Hal solubility was increased 20-fold in the presence of a 10-fold excess of methyl i-CD (Mei-CD) and 12-fold in the presence of a 10-fold excess of 2-hydroxypropyl i-CD (HPi-CD). The stoichiometries and stability constants of Hal-Mei-CD (1:1 and 2345 M − 1 at 27°C) and Hal -HPi-CD (1:1 and 2112 M − 1 at 27°C) complexes were calculated by the continuous variation and phase solubility methods respectively. Differential scanning calorimetry and 1 H-NMR were used to confirm the formation of inclusion complexes. Moreover, the enthalpy and entropy of the complexation process were calculated for both complexes in order to obtain such information as the main 'driving force' and whether or not complex formation is thermodynamically favoured. This was achieved by monitoring the isothermic solubility lines at various temperatures. © 1997 Elsevier Science B.V.

The adsorption of lead onto date palm fibers (palm fibers) and leaf base of palm (petiole) has been examined in aqueous solution by considering the influence of various parameters such as contact time, solution pH, adsorbent dosage, particle sizes, ionic strength, and temperature. The adsorption of Pb(II) increased with an increase of contact time. The optimal range of pH for Pb(II) adsorption is 3.0–4.5. The linear Langmuir and Freundlich models were applied to describe the equilibrium isotherms, and both models fitted well. The monolayer adsorption capacity of Pb(II) on palm fibers and petiole was found as 18.622 and 20.040 mg/g, respectively, at pH 4.5 and 25°C. Dubinin-Radushkevich (D-R) isotherm model was also applied to equilibrium data. The mean free energy of adsorption (2.397 and 4.082 kJ/mol) onto palm fibers and petiole, respectively, may be carried out via physisorption mechanism. Pseudo-first-order rate equation and pseudo-second-order rate equation were applied to study the adsorption kinetics. In comparison to first-order kinetic model, pseudo-second-order model described well the adsorption kinetics of Pb(II) onto palm fibers and petiole from aqueous solution. From the results of the thermodynamic analysis, Gibbs free energy ΔG, enthalpy change ΔH, and entropy ΔS were determined. The positive value of ΔH suggests that interaction of Pb(II) adsorbed by palm fibers is endothermic. In contrast, the negative value of ΔH indicates that interaction of Pb(II) ions by petiole is exothermic. The negative value of ΔG indicates that the adsorption of Pb(II) ions on both palm fibers and petiole is a spontaneous process.

- by Halim Khalili
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- Thermodynamics, Kinetics, Modeling, Water Pollution
- by Miguel Mussati
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- Engineering, Thermodynamics, Modeling, Heat Transfer

Expanded graphite is a promising heat transfer promoter due to its high conductivity, which improves the thermal conductivity of organic phase change materials. Moreover, it can also serve as supporting materials to keep the shape of the blends stable during the phase transition. After various investigation, the results showed that the maximum weight percentage of polyethylene glycol was as high as 90% in this paper without any leakage during the melting period, with the latent heat of 161.2 J g À1 and the melting point of 61.46°C. It was found that the value of the latent heat was related to the polyethylene glycol portion, increased with the increase in polyethylene glycol content. Moreover, the measured enthalpy of the composite phase change materials was proportional to the mass ratio of the polyethylene glycol component. The melting temperatures were almost the same with different ratios of composites. The conductivity of blends was improved significantly with the high value of 1.324 W m À1 K À1 compared to the pure polyethylene glycol conductivity of 0.2985 W m À1 K À1 .

- by Memet Kahraman
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- Engineering, Materials Engineering, Economics, Heat Transfer

Solidi®cation (supercooled nematic-to-solid or supercooled smectic-A-to-solid), melting (solid-to-nematic or solid-tosmectic-A), smectic-A-to-nematic, and clearing (nematic-to-isotropic or smectic-A-to-isotropic) transition temperatures W s , W m , W AN , and W c , respectively, and enthalpies DH s , DH m , DH AN , and DH c , respectively, have been determined by differential scanning calorimetry (DSC) for members of the p-(n-alkyl)-p H -cyanobiphenyl (RCB) and the p-(n-alkoxy)-p H -cyanobiphenyl (ROCB) homologous series of liquid crystals, where`R' is the number of carbon atoms in the n-alkyl or n-alkyloxy tails. The study shows that the transition of the less ordered nematic phase to the more ordered smectic-A phase, in liquid crystals that exhibit both phases (those with R8 or 9), involves a transient phase of intermediate order. Broad or overlapping solidi®cation exotherms indicate that two mesogenic aggregations supercool simultaneously. Finally, there is evidence for a transition between two solid forms that occurs at temperatures preceding W m or concurrent with it depending on`R' and the heating rate. This refutes an earlier view that during melting the solid form with the higher melting point solidi®es. #

At high temperature, coarse-grained (bulk) rutile is well established as the stable phase of TiO 2 , and nanophase anatase, thermodynamically stable relative to nanophase rutile, transforms irreversibly to rutile as it coarsens. The lack of experimental heat-capacity data for bulk anatase below 52 K lends uncertainty to its standard entropy and leaves open a slight possibility that anatase may have a thermodynamic stability field at low temperature, as suggested by some theoretical calculations. In the present study, the molar heat capacities of rutile and anatase were measured from 0.5 K to about 380 K. These data were combined with previously measured high-temperature heat capacities, and fits of the resulting data set were used to generate C P°,m , ∆ 0 T S m°, ∆ 0 T H m°, and ∆ 0 T G m° values at smoothed temperatures between 0.5 and 1300 K for anatase and 0.5 and 1800 K for rutile. Using these new data and the enthalpy of transformation between anatase and rutile at 298 K, the change in Gibbs free energy for the transition between anatase and rutile from 0 to 1300 K was calculated. These calculations reveal that the transformation from bulk anatase to bulk rutile is thermodynamically favorable at all temperatures between 0 and 1300 K, confirming that bulk anatase does not have a thermodynamic stability field. Implications for the natural occurrence of these two minerals in terrestrial, lunar, and planetary settings are discussed. In particular, anatase requires low-temperature aqueous conditions for its formation and may be a reliable indicator of such conditions in both terrestrial and extraterrestrial settings.

- by olgA DOROFEEVA
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- Engineering, Chemical Engineering, Geology, Geochemistry
- by Uday Ghosh
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- Chemical Engineering, Thermodynamics, Kinetics, Image Analysis

Here we report for the first time heat of ionization of invertase (E.C.3.2.1.26) active site residues from hyperproducer strain of Aspergillus niger (34.1 U ml -1 ), along with its physiochemical properties, kinetics and thermodynamics of stability-function. The Invertase showed great potential for industry as being highly efficient (k cat = 24167 s -1 at 65 °C, pH 5.0) and stable (half life= 12 h at 56°C).

- by Habib Nadeem
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- Engineering, Microbiology, Biotechnology, Entropy

This work considers the seven-coefficient polynomials proposed by the National Aeronautics and Space Administration (NASA) to facilitate obtaining a normalized value for three thermodynamic standard-state specific properties of ideal gases or condenser matters over an interval of temperature. These properties are the heat capacity at constant pressure, the absolute enthalpy (sensible enthalpy plus heat contents due to chemical or physical changes), and the entropy. In the open literature, one can find several databases for the polynomial coefficients with variation in the number of species included or the range of temperature covered, and this raises a question of whether the choice of a database to use has an important impact on these evaluated thermodynamic properties. Addressing this point, we compare and assess three databases for the NASA 7-coefficient polynomials, over a selected range of temperature from 300 K to 3500 K, and for selected six common gaseous species encountered in combustion or industrial processes, which are molecular oxygen (O 2), molecular nitrogen (N 2), molecular hydrogen (H 2), methane (CH 4), carbon dioxide (CO 2), and water vapor (H 2 O). Our comparisons suggest that despite the difference in the values of coefficients, there is no significant difference in their predictions. However, the latest (7 th edition) database of Prof. Alexander Burcat hosted at Eötvös Loránd University (ELTE) in Budapest, Hungary showed superior features when contrasted to other two databases (one accompanying the simulation package OpenFOAM 6, and another provided by the natural-gas reaction mechanism GRI-MECH 3.0).

- by Osama A Marzouk
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- Entropy, Nasa, Enthalpy, Specific Heat

An enthalpy formulation based fixed grid methodology is developed for the numerical solution of convection-diffusion controlled mushy region phase-change problems. The basic feature of the proposed method lies in the representation of the latent heat of evolution, and of the flow in the solid-liquid mushy zone, by suitably chosen sources. There is complete freedom within the me~odoIo~ for the definition of such sources so that a variety of phase-change situations can be modelled. A test problem of freezing in a thermal cavity under natural convection is used to demonstrate an application of the method.

- by Chandra Prakash
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- Engineering, Convection, Numerical Modelling, Heat and Mass Transfer

The variations of thermal conductivity with temperature for Al-[x] wt.% Cu, x = 3, 6, 15 and 24 alloys were measured by using a radial heat flow apparatus. The variations of electrical conductivity of solid phases versus temperature for the same alloys were determined from the Wiedemann-Franz and Smith-Palmer equations by using the measured values of thermal conductivity. From the graphs of thermal and electrical conductivity versus temperature, the thermal conductivity of the solid phases at their melting temperatures, and the thermal temperature and the electrical coefficients for the same alloys were obtained. Dependency of the thermal and electrical conductivity on the composition of Cu in the Al based AlÀCu alloys were also investigated. According to present experimental results, the thermal and electrical conductivity of Al-[x] wt.% Cu, x = 3, 6, 15 and 24 alloys linearly decrease with increasing the temperature and composition of Cu. The enthalpy of fusion and the specific heat change during the transformation for the same alloys were determined from cooling trace during the transformation from eutectic liquid to eutectic solid by means of differential scanning calorimeter (DSC).

This paper reports the results of measurements of the densities of binary mixtures of cyclohexane with hexane using a high pressure stainless steel pycnometer system at various temperatures between 298.15 K and 473.15 K. The results were compared with those predicted by the Hankinson-Brobst-Thomson correlation (HBT) and the Spencer and Danner modified Rackett equation (SDR). The HBT equation showed an average deviation of about 0.36% from the experimental results while the SDR equation showed a 0.15% average absolute deviation. The excess molar volumes, V E, calculated from the density values have been found to change from positive to negative values with the increase of temperature.

- by Nasiru Tukur
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- Chemical Engineering, High Pressure, Density, Classical Physics

Preservation of liquid foods by high intensity pulsed electric fields (PEF) is an interesting alternative to traditional techniques like thermal pasteurization. Based on the underlying mechanism of action, in this paper the crucial process parameters electrical field strength, total pulse energy input and treatment temperature were investigated experimentally. Inactivation studies were performed with three bacteria (E. coli, Bacillus megaterium, Listeria innocua) and one yeast (Saccharomyces cerevisiae). Stainless steel and carbon electrodes have been tested to investigate their applicability as electrode material. Simulating the influence of cell size and orientation as well as the presence of agglomerations or insulating particles indicated that the applied field strength has to be increased above the critical one to achieve product safety. It was found that temperatures higher than 40 • C can strongly increase the lethality of the PEF process. In this way also small cells like Listeria are easily affected by pulsed fields even at a field strength as low as 16 kV cm −1 . In addition, heating of the product prior to PEF has the advantage that most of the required process energy can be recovered using heat exchangers. Exemplary, such a process is analyzed by an enthalpy balance.

- by V. Heinz
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- Chemical Engineering, Heat Exchanger, Pulsed Electric Field, Saccharomyces cerevisiae

Chemistry HL IB IA: higher level internal assessment

- by Angel Versetti
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- Physics, Thermodynamics, Chemistry, Analytical Chemistry

The effect of high-pressure (HP) treatment (100–400 MPa for 15 or 30 min at 20 °C) on the rheological characteristics and colour of fresh and canned mango pulps was evaluated. Differences were observed in the rheological behaviour of fresh and canned mango pulps treated with HP. Shear stress–shear rate data of pulps were well described by the Herschel–Bulkley model. The consistency index (K) of fresh pulp increased with pressure level from 100 to 200 MPa while a steady decrease was noticed for canned pulp. For fresh pulp the flow behaviour index decreased with pressure treatment whereas an increasing trend was observed with canned pulp. Storage and loss moduli of treated fresh pulp with HP increased linearly with angular frequency up to 200 MPa for a treatment time of 30 min while a steady decreasing trend was found for processed pulp. No significant variation in colour was observed during pressure treatment.

- by Hosahalli Ramaswamy
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- Engineering, High Pressure, Rheology, FTIR spectroscopy

Changes in melting points, enthalpy, and specific heat capacity of catfish visceral oil at each step of the purification process were studied. Melting points of -46.2 to 21.2°C for crude oil, -45.9 to 11.5°C for degummed oil, -44.3 to 11.4°C for neutralized oil, -47.1 to 9.9°C for bleached oil and -52.3 to 8.0°C for deodorized oil were observed. Enthalpy (kJ/kg) was 74.1 for crude oil, 74.7 for degummed oil, 75.1 for neutralized oil, 79.3 for bleached oil, and 84.3 for deodorized oil. The specific heat capacities at 20°C for crude, degummed, neutralized, bleached, and deodorized oils were 1.69, 1.96, 1.97, 1.91, and 1.83 kJ/kg°C, respectively.

- by Ioan I Negulescu
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- Chemical Engineering, Enthalpy, Fish Oil, Heat Capacity

A comprehensive treatment of the thermodynamics of cyclic magnetic refrigeration processes is presented. It starts with a review of the work, heat and internal energy of a magnetized specimen in a magnetic field, and a list of the thermodynamic potentials is given. These are based on the very recent discovery of an alternative Kelvin force. It is shown that this force is compatible with the internal energy proposed by Landau and Lifshitz. New formulas for the specific enthalpies are presented. Cyclic processes are discussed in detail, e.g. the Brayton, Ericsson and Carnot cycles. Magnetic refrigeration and magnetic heat pump cycles are preferably designed by applying the cascade or/and regeneration principle. Cascade systems allow wider temperature ranges to be obtained. The main objective of this article is to yield a theoretical basis for an optimal design of new magnetic refrigeration and heat pump devices. q

- by Peter Egolf
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- Engineering, Thermodynamics, Design, Refrigeration
- by Badr Habeebullah
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- Engineering, Production, Modeling, Prediction

The Awibengkok geothermal field, also known as Salak, is the largest developed geothermal resource in Indonesia, currently sustaining 377 MW of electrical generation. It is a water-dominated, naturally fractured reservoir with benign fluid chemistry. A very large amount of produced brine is injected along the margins of the proven reservoir. After 13 years of continuous operation, production levels have been maintained at or above nominal turbine capacity through periodic make-up drilling and field management. The two main challenges have been taking advantage of the changing reservoir thermodynamic conditions and managing injection. Some innovations in well design and drilling procedures include sizing up the production casing from 9 5 8 in. to 13 3 8 in. with 13 3 8 in. and 16 in. tie-backs, and drilling shallow, relatively high-angle (55-60 • inclination) wells to maximize production from the steam cap. Well deliverability predictions have been improved by combining well production history and downhole measurements to construct wellbore hydraulic models.

- by Jorge Acuña and +2
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- Management, Geology, Geophysics, Thermodynamics

— This experiment aimed determining the enthalpy of neutralization for the strong acid-strong base and weak acid-strong base reactions. Coffee-cup calorimetry was applied to equimolar concentrations of both hydrochloric acid and acetic acid with sodium hydroxide. From the calculated heat capacity of solution, it was found out that the reaction of strong acid-strong base reaction had a mean enthalpy of neutralization of-74844.25 kJ/mol, yielding a percentage error of 28.18%. W eak acid neutralization yielded a value of –73.60 kJ/mol-a percentage error of 12.43%. In the analysis it is assumed that a linear relationship exists in the extrapolation of the final temperature, necessitating stabilities in temperature determinations.

- by Jonniel Vince Cruz
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- Thermodynamics, Enthalpy, Heat Capacity, Calorimetry

The various state functions that are measurable thermodynamic parameters have been defined and fully explained. The exact differentials of each of the state functions have been derived and their applications clearly examined. The Maxwell Reciprocity Relations have been explained and assessed as to how it provides the conditions for the exactness of each of the state functions. Hence, the application of Maxwell's Relation leads to the provision of new additional thermodynamic formula which is very useful and simple.

- by Nsikak-Jeuel J Ituh
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- Thermodynamics, Classical Thermodynamics, Energy, Chemical thermodynamics

Literature data for the solubility of lithium chloride salts (anhydrous LiCl, LiCl‚H 2 O, LiCl‚2H 2 O, LiCl‚ 3H 2 O, and LiCl‚5H 2 O) in pure water have been compiled and critically evaluated. These data have been represented by empirical temperature-molality expressions from which the coordinates of the eutectics and of the peritectics have been calculated. The thermodynamic properties of the LiCl salts have been calculated from their solubilities in pure water using two different models of aqueous LiCl solutions (Pitzer's ion interaction model and the mean spherical approximation model) which allow the calculation of the activity of water and of the LiCl(aq) activity coefficient to very low temperatures (199 K) and/or very high concentrations (up to 30 M), characteristic of the LiCl + H 2 O system. The water-ice equilibrium constant has been determined to 199 K. Results of the Pitzer-Holmes-Mesmer ion interaction model are reliable only for LiCl molalities below 11 M. At higher molalities (corresponding to the solubilities of LiCl‚2H 2 O(s), of LiCl‚H 2 O(s), and of anhydrous LiCl for temperatures between 273 and 433 K), the mean spherical approximation model has been used. Entropies and standard enthalpies of formation of the various solids have been retrieved from fits of their solubility products with respect to temperature. Our values are in good agreement with the NBS values. There is a linear correlation between the entropies and standard enthalpies of formation and the number of water molecules in the LiCl hydrates, as already reported for MgCl 2 ‚nH 2 O, MgSO 4 ‚nH 2 O, and Na 2 CO 3 ‚nH 2 O.

- by Nicolas Papaiconomou
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- Chemical Engineering, Thermodynamics, Water, Chemical

The aim of the methods described is to calculate the properties of turbulent reactive flow fields. At each point in the flow field, a complete statistical description of the state of the fluid is provided by the velocity-composition joint pdf. This is the joint probability density function (pdf) of the three components of velocity and of the composition variables (species mass fractions and enthalpy). The principal method described is to solve a modelled transport equation for the velocity-composition joint pdf. For a variable-density flow with arbitrarily complex and nonlinear reactions, it is remarkable that in this equation the effects of convection, reaction, body forces and the mean pressure gradient appear exactly and so do not have to be modelled. Even though the joint pdf is a function of many independent variables, its transport equation can be solved by a Monte Carlo method for the inhomogeneous flows of practical interest. A second method that is described briefly is to solve a modelled transport equation for the composition joint pdf.The objective of the paper is to provide a comprehensive and understandable of the theoretical foundations of the pdf approach.

The kinetics and mechanism of methylene blue adsorption onto raw pine cone biomass (Pinus radiata) was investigated under various physicochemical parameters. The extent of the methylene blue dye adsorption increased with increases in initial dye concentration, contact time and solution pH but decreases with the amount of adsorbent, salt concentration and temperature of the system. Overall the kinetic studies showed that the methylene blue adsorption process followed pseudo-second-order kinetics among various kinetic models tested. The different kinetic parameters including rate constant, half-adsorption time and diffusion coefficient are determined at different physicochemical conditions. Equilibrium data were best represented by Langmuir isotherm among Langmuir and Freundlich adsorption isotherm. The maximum monolayer adsorption capacity of pine cone biomass was 109.89 mg/g at 30°C. The value of separation factor, R L, from Langmuir equation and Freundlich constant, n, both give an indication of favourable adsorption. Thermodynamic parameters such as standard Gibbs free energy (∆G 0), standard enthalpy (∆H 0), standard entropy (∆S 0) and the activation energy (A) were calculated. A single-stage batch absorber design for the methylene blue adsorption onto pine cone biomass has been presented based on the Langmuir isotherm model equation.

- by Sharmeen Afroze
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- Kinetics, Biomass, Modeling, Multidisciplinary

Activated (AC-PW) and non-activated (C-PW) carbonaceous materials were prepared from the Brazilian pine-fruit-shell (Araucaria angustifolia) and tested as adsorbents for the removal of Procion Red MX 3B dye (PR-3B) from aqueous effluents. The activation process lead to increase in the specific surface area, average porous volume, and average porous diameter of the adsorbent AC-PW when compared to C-PW. The effects of shaking time, adsorbent dosage and pH on adsorption capacity were studied. PR-3B uptake was favorable at pHs ranging from 2.0 to 3.0 for C-PW and 2.0 to 7.0 for AC-PW. The contact time required to obtain the equilibrium using C-PW and AC-PW as adsorbents was 6 and 4 h at 298 K, respectively. The values of the function error (F error ) of fractionary-order kinetic model was at least 15 times lower than the values obtained with pseudo-first-order, pseudo-second order and Elovich kinetic models, indicating that this kinetic model was better fitted to the experimental results. For equilibrium data the F error values of the Sips isotherm model were at least 4.0 lower than the values of Langmuir, Freundlich, and Redlich-Peterson isotherm models using C-PW and AC-PW as adsorbents. The enthalpy and entropy of adsorption of PR-3B were obtained from adsorption experiments ranging from 298 to 323 K. Simulated dyehouse effluents were used to check the applicability of the proposed carbons for effluent treatment.

- by Eder Lima and +1
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- Chemical Engineering, Thermodynamics, Kinetics, Modeling
- by Jason R V Sellers
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- Surface Science, Catalysis, Entropy, Adsorption

- by Chandra Prakash
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- Engineering, Convection, Numerical Modelling, Heat and Mass Transfer

The sublimation enthalpy and entropy of urea and its derivatives monomethylurea (mmu), monoethylurea (meu), monopropylurea (mpu), dimethyl-1,1-urea (1,1-dmu), dimethyl-1,3-urea (1,3-dmu), and diethyl-1,3-urea (1,3-deu) were determined from the dependence of their vapour pressures on temperature. The vapour pressures were measured by the torsion-effusion method. The corresponding pressure against temperature equations are: urea, ; mmu, ; meu, mpu, ; 1,1-dmu, ; 1,3-dmu, ; 1,3-deu, ; where the errors associated with the slopes (±100) and intercepts (±0.18), (±0.30 for urea), were estimated.

- by daniela ferro
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- Chemical Engineering, Bioinformatics, Thermodynamics, Life Sciences

Adsorption of methylene blue from aqueous solutionsonto unexpanded and expanded perlite samples activatedby H2SO4 and NaCl solutions has beeninvestigated, to assess the possibility of usingperlite for removing cationic dyes from aqueoussolutions. The effects of pH and temperature of dyesolution on the adsorption capacities have beenevaluated. The experimental data were correlatedreasonably well by the Langmuir adsorption isothermand the isotherm parameters (Q m and K) have beencalculated. The removal efficiency (P) anddimensionless separation factor (R) have shown thatperlite can be used for removal of methylene blue fromaqueous solutions, but unexpanded perlite is more effective.

- by Yavuz Alkan
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- Environmental Engineering, Chemical Engineering, Civil Engineering, Thermodynamics

The adsorption of Cr(VI) was studied in batch system using fruits of Ficus glomerata as adsorbent. The effect of temperature, pH, initial Cr(VI) concentration and time was investigated. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) was used to investigate surface morphology and active functional groups present on the adsorbent surface. Thermodynamic parameters like free energy change ( G 0 ), enthalpy ( H 0 ) and entropy ( S 0 ) indicate the spontaneous, endothermic and increased randomness nature of Cr(VI) adsorption. Equilibrium data were fitted well with Langmuir isotherm at 50 • C. The magnitude of mean free energy indicates chemical nature of adsorption. The breakthrough and exhaustive capacities were found to be 5 and 23.1 mg g −1 respectively. The applicability of the adsorbent has been demonstrated by removing Cr(VI) from electroplating wastewater.

- by Rifaqat Rao
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- Engineering, Thermodynamics, Metallurgy, Water Purification
- by Tamez Uddin
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- Environmental Engineering, Chemical Engineering, Civil Engineering, Thermodynamics

Elpresente práctico tiene como objetivo principal determinar el calor de combustión a dilución infinita de una sal de magnesio en ácido clorhídrico. Para ello se verá el cambio de temperatura en el tiempo; primero se verá como es la variación de temperatura al añadir agua destilada y posteriormente el cambio que ocurre al agregar 3 tipos diferentes de sal (cloruro de amonio, oxido de magnesio y magnesio). Calculando los moles de sal que se debe agregar para 200 moles de agua y el posterior cálculo de ΔT de las sales, finalmente mediante una ley de Hess se podrá calcular el calor de combustión del magnesio, con los ΔformH calculados de las sales de Mg y MgO.

- by Mathius Sanhueza Silva
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- Thermodynamics, Enthalpy, Fisicoquímica, Standard Enthalpy

The heat capacity of crystalline S-D-glucose has been measured at temperatures from 7 K to 347 K with an adiabatic calorimeter. Heat capacity, entropy, enthalpy increments, and values of (TA~S~--AT98.IsKH~)/RT are reported at smoother... more

Adsorptionldesorption on a smooth surface is studied at the molecular level by new, simple two-dimensional Monte Carlo simulation procedures using site-specific adsorptiorddesorption probabilities. The classical BET conditions are simulated and the resulting adsorption isotherms show a very good fit with the calculated theoretical parameters of the equation. The BET islands are visualized and analyzed. Following this test simulation, lateral interactions are added, resulting in type I1 and type 111 isotherms. The ensuing deviations from BET behavior are identified and analyzed. It is shown that accurate surface area values can only be obtained from an unequivocal B-point. The effects of changes in adsorption1 desorption probabilities on the isotherm shapes are identified and discussed. The changes in the heat of adsorption with coverage are analyzed. It is found that this type of plot is a very sensitive analytical tool for locating the monolayer value.

- by David Avnir
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- Multidisciplinary, Adsorption, Heterogeneity, Simulation

This paper describes the adsorption of heavy metal ions from aqueous solutions by oak (Quercus coccifera) sawdust modified by means of HCl treatment. Our study tested the removal of three heavy metals: Cu, Ni, and Cr. The optimum shaking speed, adsorbent mass, contact time, and pH were determined, and adsorption isotherms were obtained using concentrations of the metal ions ranging from 0.1 to 100 mg L −1 . The adsorption process follows pseudo-second-order reaction kinetics, as well as Langmuir and D-R adsorption isotherms. The paper discusses the thermodynamic parameters of the adsorption (the Gibbs free energy, entropy, and enthalpy). Our results demonstrate that the adsorption process was spontaneous and endothermic under natural conditions. The maximum removal efficiencies were 93% for Cu(II) at pH 4, 82% for Ni(II) at pH 8, and 84% for Cr(VI) at pH 3.

- by Sukru Dursun
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- Engineering, Thermodynamics, Kinetics, Entropy

Experiments were carried out to evaluate the batch adsorption of phenol from petroleum refinery wastewater on a locally prepared date-pit activated carbon (DP-AC). Adsorption equilibrium and kinetics data were determined for the uptake of phenol from real refinery wastewater and from synthetically prepared aqueous phenol solution. The data were fitted to several adsorption isotherm and kinetics models. Sips as well as Langmuir models gave the best fit for equilibrium isotherms, whereas the kinetics data were best fitted by the pseudo-second order model. The enthalpy of adsorption showed an exothermic nature of the adsorption process. Several chemical and thermal techniques were tested for the regeneration of saturated activated carbon; using ethanol was found to be the most effective with more than 86% regeneration efficiency after four regeneration cycles.

- by Sulaiman Al-Zuhair
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- Chemical Engineering, Regeneration, Kinetics, Modeling

This work considers the seven-coefficient polynomials proposed by the National Aeronautics and Space Administration (NASA) to facilitate obtaining a normalized value for three thermodynamic standard-state specific properties of ideal gases or condenser matters over an interval of temperature. These properties are the heat capacity at constant pressure, the absolute enthalpy (sensible enthalpy plus heat contents due to chemical or physical changes), and the entropy. In the open
literature, one can find several databases for the polynomial coefficients with variation in the number of species included or the range of temperature covered, and this raises a question of whether the choice of a database to use has an important impact on these evaluated thermodynamic properties. Addressing this point, we compare and assess three databases for the NASA 7-coefficient polynomials, over a selected range of temperature from 300 K to 3500 K, and for selected six common gaseous species encountered in combustion or industrial processes, which are molecular oxygen (O2 ), molecular nitrogen (N2
), molecular hydrogen (H2), methane (CH4), carbon dioxide (CO2), and water vapor (H2O). Our comparisons suggest that despite the difference in the values of coefficients, there is no significant difference in their predictions. However, the latest (7th edition) database of Prof. Alexander Burcat hosted at Eötvös Loránd University (ELTE) in Budapest, Hungary
showed superior features when contrasted to other two databases (one accompanying the simulation package OpenFOAM 6, and another provided by the natural-gas reaction mechanism GRI-MECH 3.0).

- by Kanwal Sandhu
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- Environmental Engineering, Chemical Engineering, Civil Engineering, Thermodynamics

Tartrazine, a yellow menace, is widely being used in cosmetics, foodstuffs, medicines and textile. It is carcinogenic and also catalyzes allergic problems. In the present work the ability to remove Tartrazine from aqueous solutions has been studied using waste material-hen feathers, as adsorbent. Effects of pH, concentration of the dye, temperature and adsorbent dosage have been studied. Equilibrium isotherms for the adsorption of the dye were measured experimentally. Results were analyzed by the Freundlich and Langmuir equation at different temperatures and determined the characteristic parameters for each adsorption isotherm. The adsorption process has been found endothermic in nature and thermodynamic parameters, Gibb's free energy (G •), change in enthalpy (H •) and change in entropy (S •) have been calculated. The paper also includes results on the kinetic measurements of adsorption of the dye on hen feathers at different temperatures. By rate expression and treatment of data it has been established that the adsorption of Tartrazine over hen feathers follows a first-order kinetics and a film diffusion mechanism operates at all the temperatures.

- by Lisha Kurup
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- Engineering, Kinetics, Entropy, Adsorption

Molar heat capacities at constant pressure, C p,m , of 11 primary alkylamides (butanamide, 2-methylpropanamide, pentanamide, 2,2-dimethylpropanamide, hexanamide, octanamide, decanamide, dodecanamide, hexadecanamide, octadecanamide, docosanamide) determined by differential scanning calorimetry (DSC) increased as a function of temperature and were fitted into linear equations. Values at 298.15 K obtained by interpolating/extrapolating the smoothed equations displayed a linear increase with the number of carbon atoms. The C p,m contribution of the CH 2 group was (22.5 ( 0.7) J · K -1 · mol -1 , in agreement with our previous results for linear alkane-R,ω-diamides and alkane-R,ω-diols as well as with the literature data for various series of linear alkyl compounds. Temperatures, enthalpies, and entropies of the solid-solid transitions and fusion of alkylamides were also determined. They are discussed with reference to the packing patterns described in the literature.

- by elena badea and +2
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- Chemical Engineering, Differential scanning calorimetry, Enthalpy, Heat Capacity

The barrier to rotation about the C2-C3 bond in n-butane has been calculated using several basis sets, complete geometry optimization, and correction for electron correlation. Neither the basis set size nor inclusion of electron correlation has a large effect on the magnitude of the rotational barrier or the trans/gauche energy difference. After correction for zero-point energy differences, the former is found to be 6.34 kcal/mol, while the latter is 0.86, in very good agreement with the experimental value. The trans/gauche energy difference in n-pentane is the same as that for butane, and similar values are found for the two gauche forms of n-hexane and the symmetrical gauche form of octane. The structures and energies of several conformers of pentane and hexane with two and three gauche fragments also have been obtained. It is found that the pentane rotamer with two consecutive gauche kinks has roughly twice the gauche energy, but the hexane conformer with three consecutive gauche kinks has considerably less than 3 times that value. The energy differences for the rotamers of 2-methylbutane and 2,3-dimethylbutane are well reproduced by the calculations. Vibrational frequencies are estimated at the 3-21G level for all species, and the zero-point energies and enthalpy changes (H298 -Ho) are calculated. The difference in enthalpy between an axial and equatorial methyl substituent on cyclohexane is calculated to be 2.17 kcal/mol after correcting for vibrational energy differences. The relationship between the energy of a methylene group in cyclohexane and in trans-n-alkanes is examined.

- by Mark Murcko
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- Information, Data, Enthalpy, Zero Point Energy