On the characterization of fluxes in nonlinear irreversible thermodynamics

The linear Onsager theory of irreversible thermodynamics is extended to include nonlinear phenomenological relations by means of Onsager fluxes. Such fluxes satisfy a full system of reciprocity relations, vanish in thermodynamic equilibrium, and give a non-negative production of entropy. A complete characterization of Onsager fluxes is obtained in terms of non-negative scalar valued functions which vanish in thermodynamic equilibrium. These same functions are also shown to characterize all C² fluxes which satisfy the second law of thermodynamics. Each system of Onsager fluxes is shown to derive from a dissipation function which attains its absolute minimum in thermodynamic equilibrium. The reaction rates given by reaction kinetics are shown to be Onsager fluxes and their dissipation functions are explicitly calculated.     

Statistical characterization of polycrystalline ferrite media

The classical field theory superposition principle, the central limit theorem, and the gyromagnetic equations of motion are invoked as a basis to formulate a quasi-static statistical model for polycrystalline ferrite media with Gaussian statistics. The use of this model to analyze small signal reversible rotational phenomena is illustrated. It is also demonstrated that this model and a previous microwave model given by the authors are maximum entropy models An analogy between the maximum entropy property of these models and the Gibbs thermodynamic equivalence for equilibrium and a state of maximum entropy is noted.     

Basic Operation of Cryocoolers and Related Thermal Machines

This paper deals with the basics of cryocoolers and related thermodynamic systems. The treatment is based on the first and second law of thermodynamics for inhomogeneous, open systems using enthalpy flow, entropy flow, and entropy production. Various types of machines, which use an oscillating gas flow, are discussed such as: Stirling refrigerators, GM coolers, pulse-tube refrigerators, and thermoacoustic coolers and engines. Furthermore the paper deals with Joule-Thomson and dilution refrigerators which use a constant flow of the working medium.     

Diagrams of entropy for ammonia–water mixtures: Applications to absorption refrigeration systems

The objective of this work is to calculate the entropy of ammonia–water mixture as a function of temperature, pressure, concentration, and other thermodynamic properties associated to absorption process, to support energy and exergy analysis of absorption refrigeration systems. This calculation is possible because a novel mathematical modelling was developed for this attempt. This determination will allow simulation and optimisation of absorption refrigeration systems, giving major importance in determining the values of thermodynamic properties of ammonia–water mixtures, such as enthalpy and entropy. A mathematical modelling for thermodynamics properties calculation at liquid and vapour phases of ammonia–water system is developed. The studies were based on the enthalpy vs. concentration diagram obtaining the enthalpy in the liquid phase corresponding at a temperature range from 80 °C to −40 °C. The mixtures enthalpy values were calculated for ammonia (h_1c) and water (h_2c) by using a non-linear regression program. The evaluation of thermodynamic properties in this work was discretised by formulating appropriate equations for each type of substance. However, thermodynamic properties of mixtures can be determined based on data from simple substances and mixing laws, or from an equation of state that considers the mixture concentration. The consistency of experimental data indicates the most suitable method to be used in entropy calculation.     

Removal of cadmium from wastewater using agricultural waste 'rice polish'

A novel biosorbent rice polish has been successfully utilized for the removal of cadmium(II) from wastewater. The maximum removal of cadmium(II) was found to be 9.72 mg g(-1) at pH 8.6, initial Cd(II) concentration of 125 mg l(-1) and temperature of 20 degrees C. The effect of different parameters such as contact time, adsorbate concentration, pH of the medium and temperature were investigated. Dynamics of the sorption process were studied and the values of rate constant of adsorption, rate constant of intraparticle diffusion and mass transfer coefficient were calculated. Different thermodynamic parameters, viz., changes in standard free energy, enthalpy and entropy have also been evaluated and it has been found that the reaction was spontaneous and exothermic in nature. The applicability of Langmuir isotherm showed monolayer coverage of the adsorbate on the surface of adsorbents. A generalised empirical model was proposed for the kinetics at different initial concentrations. The data were subjected to multiple regression analysis and a model was developed to predict the removal of Cd(II) from wastewater.     

Thermodynamische Fundamentalgleichungen und charakteristische Funtionen

According to J.W. Gibbs, all thermodynamic properties of a fluid phase can be calculated from a single fundamental equation of state. Such an equation can be constructed with different pairs of independent properties and their proper characteristic functions. The thermodynamic theory of the characteristic functions and their selection for the use in a fundamental equation is discussed. Only two characteristic functions are suited for the analytical representation of the complete range of all fluid states: the Massieu-function (or the equivalent Helmholtz-function) as a function of temperature and volume, and the enthalpy as a function of pressure and entropy. The methods suited for establishing a fundamental equation with the dimensionless Massieu-function are described. A historical retrospect concerning the origin and the further development of fundamental equations and characteristic functions is presented.     

Adsorption of reactive dye from an aqueous solution by chitosan: isotherm, kinetic and thermodynamic analysis

The adsorption of Remazol black 13 (Reactive) dye onto chitosan in aqueous solutions was investigated. Experiments were carried out as function of contact time, initial dye concentration (100-300mg/L), particle size (0.177, 0.384, 1.651mm), pH (6.7-9.0), and temperature (30-60 degrees C). The equilibrium adsorption data of reactive dye on chitosan were analyzed by Langmuir and Freundlich models. The maximum adsorption capacity (qm) has been found to be 91.47-130.0mg/g. The amino group nature of the chitosan provided reasonable dye removal capability. The kinetics of reactive dye adsorption nicely followed the pseudo-first and second-order rate expression which demonstrates that intraparticle diffusion plays a significant role in the adsorption mechanism. Isotherms have also been used to obtain the thermodynamic parameters such as free energy, enthalpy and entropy of adsorption. The positive value of the enthalpy change (0.212kJ/mol) indicated that the adsorption is endothermic process. The results indicate that chitosan is suitable as adsorbent material for adsorption of reactive dye form aqueous solutions.     

Chromium(VI) adsorption from aqueous solution by Hevea Brasilinesis sawdust activated carbon

Adsorption capacity of Cr(VI) onto Hevea Brasilinesis (Rubber wood) sawdust activated carbon was investigated in a batch system by considering the effects of various parameters like contact time, initial concentration, pH and temperature. Cr(VI) removal is pH dependent and found to be maximum at pH 2.0. Increases in adsorption capacity with increase in temperature indicate that the adsorption reaction is endothermic. Based on this study, the thermodynamic parameters like standard Gibb's free energy (DeltaG degrees ), standard enthalpy (DeltaH degrees ) and standard entropy (DeltaS degrees ) were evaluated. Adsorption kinetics of Cr(VI) ions onto rubber wood sawdust activated carbon were analyzed by pseudo first-order and pseudo second-order models. Pseudo second-order model was found to explain the kinetics of Cr(VI) adsorption most effectively. Intraparticle diffusion studies at different temperatures show that the mechanism of adsorption is mainly dependent on diffusion. The rate of intraparticle diffusion, film diffusion coefficient and pore diffusion coefficient at various temperatures were evaluated. The Langmuir, Freundlich and Temkin isotherm were used to describe the adsorption equilibrium studies of rubber wood sawdust activated carbon at different temperatures. Langmuir isotherm shows better fit than Freundlich and Temkin isotherm in the temperature range studied. The result shows that the rubber wood sawdust activated carbon can be efficiently used for the treatment of wastewaters containing chromium as a low cost alternative compared to commercial activated carbon and other adsorbents reported.     

On compressible Korteweg fluid-like materials

We provide a thermodynamic basis for compressible fluids of a Korteweg type that are characterized by the presence of the dyadic product of the density gradients ∇? ⊗ ∇? in the constitutive equation for the Cauchy stress. Our approach does not need to introduce any new or non-standard concepts such as multipolarity or interstitial working and is based on prescribing the constitutive equations for two scalars: the entropy and the entropy production. In comparison with the Navier-Stokes-Fourier fluids we suppose that the entropy is not only a function of the internal energy and the density but also of the density gradient. The entropy production takes the same form as for a Navier-Stokes-Fourier fluid. For a Navier-Stokes-Fourier fluid one can express the entropy production equivalently in terms of either thermodynamic affinities or thermodynamic fluxes. Following the ideas of K.R. Rajagopal concerning the systematic development of implicit constitutive theory and primary role of thermodynamic fluxes (such as force) that are cause of effects in thermodynamic affinities (such as deformation) in considered processes, we further proceed with a constitutive equation for entropy production expressed in terms of thermodynamic fluxes. The constitutive equation for the Cauchy stress is then obtained by maximizing the form of the rate of entropy production with respect to thermodynamic fluxes keeping as the constraint the equation expressing the fact that the entropy production is the scalar product of thermodynamic fluxes and thermodynamic affinities. We also look at how the form of the constitutive equation changes if the material in question is incompressible or if the processes take place at constant temperature. In addition, we provide several specific examples for the form of the internal energy and make the link to models proposed earlier. Starting with fully implicit constitutive equation for the entropy production, we also outline how the methodology presented here can be extended to non-Newtonian fluid models containing the Korteweg tensor in a straightforward manner.     

The Correlation between the Thermodynamic Functions of Molten Binary Systems of Alkali Metals

Differential thermodynamic equations are used to reveal, in the general form, the correlation between some excess thermodynamic functions of liquid solutions. It is demonstrated that a certain correlation is observed in wide ranges of temperature and concentrations between the calculation and experimental data on excess molar enthalpy and specific volume of molten Na-K and K-Cs systems.     

Determination of kinetic and equilibrium parameters of the batch adsorption of Mn(II), Co(II), Ni(II) and Cu(II) from aqueous solution by black carrot (Daucus carota L.) residues

In this study, the effect of temperature on the adsorption of Mn(II), Ni(II), Co(II) and Cu(II) from aqueous solution by modified carrot residues (MCR) was investigated. The equilibrium contact times of adsorption process for each heavy metals-MCR systems were determined. Kinetic data obtained for each heavy metal by MCR at different temperatures were applied to the Lagergren equation, and adsorption rate constants (kads) at these temperatures were determined. These rate constants related to the adsorption of heavy metal by MCR were applied to the Arrhenius equation, and activation energies (Ea) were determined. In addition, the isotherms for adsorption of each heavy metal by MCR at different temperatures were also determined. These isothermal data were applied to linear forms of isotherm equations that they fit the Langmuir adsorption isotherm, and the Langmuir constants (qm and b) were calculated. b constants determined at different temperatures were applied to thermodynamic equations, and thermodynamic parameters such as enthalpy (Delta H), free energy (Delta G), and entropy (Delta S) were calculated and these values show that adsorption of heavy metal on MCR was an endothermic process and process of adsorption was favoured at high temperatures.     

Kinetics and equilibrium adsorption studies of dimethylamine (DMA) onto ion-exchange resin

The fine grained resin ZGSPC106 was used to adsorb dimethylamine (DMA) from aqueous solution in the present research. Batch experiments were performed to examine the effects of initial pH of solution and agitation time on the adsorption process. The thermodynamics and kinetics of adsorption were also analyzed. The maximum adsorption was found at natural pH of DMA solution and equilibrium could be attained within 12 min. The equilibrium adsorption data were conformed satisfactorily to the Langmuir equation. The evaluation based on Langmuir isotherm gave the maximal static saturated adsorption capacity of 138.89 mg/g at 293K. Various thermodynamic parameters such as free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) showed that the adsorption was spontaneous, endothermic and feasible. DMA adsorption on ZGSPC106 fitted well to the pseudo-second-order kinetic model. Furthermore, the adsorption mechanism was discussed by Fourier transform infrared spectroscopy (FT-IR) analysis.     

Protein redox potential measurements based on kinetic analysis with mediated continuous-flow column electrolytic spectroelectrochemical technique. Application to TTQ-containing methylamine dehydrogenase

Kinetic determination of protein redox potentials with a mediated continuous-flow column electrolytic spectroelectrochemical technique (CFCESET) is described. In this method, the redox state of the mediator is completely regulated by the continuous-flow column electrolysis, and the homogeneous redox reaction between the mediator and a protein sample in the column is monitored spectroscopically at the downstream of the column. The protein/mediator reaction is in the pseudo-first-order kinetics, and then the rate equation is analytically solved. The kinetic analysis provides the protein redox potential as well as the homogeneous rate constant. In the kinetic measurements, equilibration of the system within the column is not required, which allows the use of increased kinds of mediators. This method was successfully applied to quinoprotein methylamine dehydrogenase containing tryptophan tryptophylquinone (TTQ) as a prosthetic group. The kinetic aspect is also valuable for the thermodynamic analysis with the mediated CFCESET. The half-life time of the kinetics can be utilized to optimize the system for the attainment of the equilibrated state within the column and can provide the assurance that the system is in equilibrium.     

常用制冷工质热力性质计算数据库的开发

建立了包括湿空气、R22、R21、R12、Rll、R134a、NH3、H2O的热力性质计算数据库系统，其中热力性质计算包括温度、压力、密度、比焓、比熵、比容、汽化潜热。对R11、R12、R21、NH3、R134a的热力性质计算公式进行了修正，计算结果与文献中的数据进行比较，结果显示：数据库中除R134a和湿空气外，其他丁质的计算误差均小于0．8％，此外R22的热力性质计算程序已在制冷循环仿真模型中得到应用。     

Liquid-phase adsorption of phenols using activated carbons derived from agricultural waste material

Physical and chemical properties of activated carbons prepared from coconut shells (SAC and ATSAC) were studied. The adsorption equilibria and kinetics of phenol and 2,4-dichlorophenol from aqueous solutions on such carbons were then examined at three different temperatures (10, 25 and 40 °C). Adsorption of both phenol and 2,4-dichlorophenol increased with an increase in temperature. The experimental data were analyzed using the Langmuir and Freundlich isotherm models. Both the isotherm models adequately fit the adsorption data for both the phenols. The carbon developed through the acid treatment of coconut shells (ATSAC) exhibited relatively higher monolayer adsorption capacity for phenol (0.53 mmol g⁻¹) and 2,4-dichlorophenol (0.31 mmol g⁻¹) as compared to that developed by thermal activation (SAC) with adsorption capacity of 0.36 and 0.20 mmol g⁻¹, for phenol and 2,4-dichlorophenol, respectively. The equilibrium sorption and kinetics model parameters and thermodynamic functions were estimated and discussed. The thermodynamic parameters (free energy, enthalpy and entropy changes) exhibited the feasibility and spontaneous nature of the adsorption process. The sorption kinetics was studied using the pseudo-first-order and second-order kinetics models. The adsorption kinetics data for both the phenol and 2,4-dichlorophenol fitted better to the second-order model. An attempt was also made to identify the rate-limiting step involved in the adsorption process. Results of mass transfer analysis suggested the endothermic nature of the reaction and change in the mechanism with time and initial concentration of the adsorbate. The results of the study show that the activated carbons derived from coconut shells can be used as potential adsorbent for phenols in water/wastewater.     

Irreversibility in the two-body hard-disk lorentz gas

Time-reversible modifications of Newton's equations of motion have been used to simulate irreversible isothermal shear flows. The modified equations have stable solutions for periodic systems with as few as two or three particles. These small-system solutions exhibit thermodynamic irreversibility, entropy production and realistic nonlinear constitutive behavior.     

Kinetics and thermodynamics of cadmium ion removal by adsorption onto nano zerovalent iron particles

Nano zerovalent iron (nZVI) is an effective adsorbent for removing various organic and inorganic contaminants. In this study, nZVI particles were used to investigate the removal of Cd(2+) in the concentration range of 25-450 mg L(-1). The effect of temperature on kinetics and equilibrium of cadmium sorption on nZVI particles was thoroughly examined. Consistent with an endothermic reaction, an increase in the temperature resulted in increasing cadmium adsorption rate. The adsorption kinetics well fitted using a pseudo second-order kinetic model. The calculated activation energy for adsorption was 54.8 kJ mol(-1), indicating the adsorption process to be chemisorption. The intraparticle diffusion model described that the intraparticle diffusion was not the only rate-limiting step. The adsorption isotherm data could be well described by the Langmuir as well as Temkin equations. The maximum adsorption capacity of nZVI for Cd(2+) was found to be 769.2 mg g(-1) at 297 K. Thermodynamic parameters (i.e., change in the free energy (ΔG(o)), the enthalpy (ΔH(o)), and the entropy (ΔS(o))) were also evaluated. The overall adsorption process was endothermic and spontaneous in nature. EDX analysis indicated the presence of cadmium ions on the nZVI surface. These results suggest that nZVI could be employed as an efficient adsorbent for the removal of cadmium from contaminated water sources.