On interfacial tension calculation from the test-area methodology in the grand canonical ensemble

We propose the extension of the test-area methodology, originally proposed to evaluate the surface tension of planar fluid-fluid interfaces along a computer simulation in the canonical ensemble, to deal with the solid-fluid interfacial tension of systems adsorbed on slitlike pores using the grand canonical ensemble. In order to check the adequacy of the proposed extension, we apply the method for determining the density profiles and interfacial tension of spherical molecules adsorbed in slitlike pore with different pore sizes and solid-fluid dispersive energy parameters along the same simulation. We also calculate the solid-fluid interfacial tension using the original test-area method in the canonical ensemble. Agreement between the results obtained from both methods indicate that both methods are fully equivalent. The advantage of the new methodology is that allows to calculate simultaneously the density profiles and the amount of molecules adsorbed onto a slitlike pore, as well as the solid- fluid interfacial tension. This ensures that the chemical potential at which all properties are evaluated during the simulation is exactly the same since simulations can be performed in the grand canonical ensemble, mimicking the conditions at which the adsorption experiments are most usually carried out in the laboratory.The authors would like to acknowledge helpful discussions with B. Mendiboure. This work was supported by Ministerio de Ciencia e Innovación (MICINN, Spain) through Grant Nos. FIS2010-14866, FIS2009-07923, and FPU Ref. AP2007-02172 (J.M.M.). Further financial support from Proyecto de Excelencia from Junta de Andalucía (Grant No. P07-FQM02884) and Universidad de Huelva are also acknowledged

Effect of dispersive long-range corrections to the pressure tensor: The vapour-liquid interfacial properties of the Lennard-Jones system revisited

We propose an extension of the improved version of the inhomogeneous long-range corrections of Janecek [J. Phys. Chem. B 110, 6264–6269 (2006)], presented recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2009)] to account for the intermolecular potential energy of spherical, rigid, and flexible molecular systems, to deal with the contributions to the microscopic components of the pressure tensor due to the dispersive long-range corrections. We have performed Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of spherical Lennard-Jones molecules with different cutoff distances, rc = 2.5, 3, 4, and 5σ . In addition, we have also considered cutoff distances rc = 2.5 and 3σ in combination with the inhomogeneous long-range corrections proposed in this work. The normal and tangential microscopic components of the pressure tensor are obtained using the mechanical or virial route in combination with the recipe of Irving and Kirkwood, while the macroscopic components are calculated using the Volume Perturbation thermodynamic route proposed by de Miguel and Jackson [J. Chem. Phys. 125, 164109 (2006)]. The vapour-liquid interfacial tension is evaluated using three different procedures, the Irving-Kirkwood method, the difference between the macroscopic components of the pressure tensor, and the Test-Area methodology. In addition to the pressure tensor and the surface tension, we also obtain density profiles, coexistence densities, vapour pressure, critical temperature and density, and interfacial thickness as functions of temperature, paying particular attention to the effect of the cutoff distance and the long- range corrections on these properties. According to our results, the main effect of increasing the cutoff distance (at fixed temperature) is to sharpen the vapour-liquid interface, to decrease the vapour pressure, and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness decreases, the width of the tangential microscopic component of the pressure tensor profile increases, and the surface tension increases as the cutoff distance is larger. We have also checked the effect of the impulsive contribution to the pressure due to the discontinuity of the intermolecular interaction potential when it is cut. If this contribution is not accounted for in the calculation of the microscopic components of the pressure tensor, incorrect values of both components as well as a wrong structure along the vapour-liquid interface are obtained.The authors would like to acknowledge helpful discus- sions with J. M. Míguez, L. G. MacDowell, and M. M. Piñeiro. This work was supported by Ministerio de Ciencia e Innovación (MICINN, Spain) (Grant No. FIS2010-14866) and by Ministerio de Economía y Competitividad (MINECO) (Grant No. FIS2013-46920-C2-1-P). Further financial sup- port from Junta de Andalucía and Universidad de Huelva is also acknowledged

Universal scaling behaviour of surface tension of molecular chains

We use and extend the universal relationship recently proposed by Galliero [G. Galliero, J. Chem. Phys. 133, 074705 (2010)], based on a combination of the corresponding-states principle of Guggenheim [E. A. Guggenheim, J. Chem. Phys. 13, 253 (1945)] and the parachor approach of Macleod [J. Macleod, Trans. Faraday Soc. 19, 38 (1923)], to predict the vapour-liquid surface tension of fully flexible chainlike Lennard-Jones molecules. In the original study of Galliero, the reduced surface tension of short-chain molecules formed by up to five monomers is expressed as a unique function of the difference between the liquid and vapour coexistence densities. In this work, we extend the applicability of the recipe and demonstrate that it is also valid for predicting the surface tension of two different chainlike molecular models, namely, linear tangent chains that interact through the Lennard-Jones intermolecular potential and fully flexible chains formed by spherical segments inter- acting through the square-well potential. Computer simulation data for vapour-liquid surface tension of fully flexible and rigid linear Lennard-Jones, and fluid flexible square-well chains is taken from our previous works. Our results indicate that the universal scaling relationship is able to correlate short- and long-chain molecules with different degrees of flexibility and interacting through different inter- molecular potentials.The authors would like to acknowledge helpful discus- sions with B. Mendiboure, D. Bessières, F. Plantier, M. M. Piñeiro, and J. M. Míguez. This work was supported by Ministerio de Ciencia e Innovación (MICINN, Spain) through Grants Nos. FIS2010-14866 and FIS2010-22047-C05-05. Further financial support from Proyecto de Excelencia from Junta de Andalucía (Grant No. P07-FQM02884), Comunidad Autónoma de Madrid (Grant No. MODELICO-P2009EPS-1691), and Universidad de Huelva are also acknowledged

Kinetic of Pyrite thermal degradation 1 under oxidative environment

Pyrite is the most common mineral in polymetallic sulphides ores. In order to apply the combustion group theory to the pyrometallurgical processes that occur in the reaction shaft, it is necessary to know the kinetic processes that happen in pyrite. In this study, thermogravimetric analysis was carried out under oxidative atmospheric conditions with 100% O2 and a heating ramp of 5, 10, 15 and 20 °C min−1. The material used was pyrite with a grain size of 63–125 μm. From the thermogravimetric data, we got the kinetic parameters of the oxidative reactions of pyrite. The different kinetic methods used in this study have been E1641-16 ASTM, Ozawa–Flynn–Wall, Kissinger–Akahira–Sunose and Friedman. These methods were used for obtaining the kinetic parameters through regression analysis, sum of squares, mean residuals between experimental and calculated values and Student coefficient (95%) and to determine which kinetic method is the most suitable to describe the kinetics of pyrite oxidation

Vapor-liquid interfacial properties of rigid-linear Lennard-Jones chains

We have obtained the interfacial properties of short rigid-linear chains formed from tangentially bonded Lennard-Jones monomeric units from direct simulation of the vapour-liquid interface. The full long-range tails of the potential are accounted for by means of an improved version of the inhomogeneous long-range corrections of Janecek [J. Phys. Chem. B 110, 6264–6269 (2006)] proposed recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2009)] valid for spherical as well as for rigid and flexible molecular systems. Three different model systems comprising of 3, 4, and 5 monomers per molecule are considered. The simulations are performed in the canonical ensemble, and the vapor-liquid interfacial tension is evaluated using the test-area method. In addition to the sur- face tension, we also obtain density profiles, coexistence densities, critical temperature and density, and interfacial thickness as functions of temperature, paying particular attention to the effect of the chain length and rigidity on these properties. According to our results, the main effect of increasing the chain length (at fixed temperature) is to sharpen the vapor-liquid interface and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness decreases and the sur- face tension increases as the molecular chains get longer. The surface tension has been scaled by critical properties and represented as a function of the difference between coexistence densities relative to the critical density.The authors would like to acknowledge helpful discus- sions with F. J. Martínez-Ruiz, E. de Miguel, C. Vega, and A. Galindo. This work was supported by Ministerio de Ciencia e Innovación (MICINN, Spain) through Grant Nos. FIS2010- 14866 (F.J.B.), FIS2009-07923 (J.M.M. and M.M.P.) and FIS2010-22047-C05-05 (L.G.M.D.). J.M.M. also acknowledges Ministerio de Ciencia e Innovación for the FPU Grant with reference AP2007-02172. Further financial support from Proyecto de Excelencia from Junta de Andalucía (Grant No. P07-FQM02884), Consellería de Educacion e Ordenacion Universitaria (Xunta de Galicia), Comunidad Autónoma de Madrid (Grant No. MODELICO-P2009/EPS-1691), and Universidad de Huelva are also acknowledged

Vapour–liquid interfacial properties of square-well chains from density functional theory and Monte Carlo simulation

The statistical associating fluid theory for attractive potentials of variable range (SAFT-VR) density functional theory (DFT) developed by [Gloor et al., J. Chem. Phys., 2004, 121, 12740–12759] is used to predict the interfacial behaviour of molecules modelled as fully-flexible square-well chains formed from tangentially-bonded monomers of diameter s and potential range l = 1.5s. Four different model systems, comprising 4, 8, 12, and 16 monomers per molecule, are considered. In addition to that, we also compute a number of interfacial properties of molecular chains from direct simulation of the vapour–liquid interface. The simulations are performed in the canonical ensemble, and the vapour– liquid interfacial tension is evaluated using the wandering interface (WIM) method, a technique based on the thermodynamic definition of surface tension. Apart from surface tension, we also obtain density profiles, coexistence densities, vapour pressures, and critical temperature and density, paying particular attention to the effect of the chain length on these properties. According to our results, the main effect of increasing the chain length (at fixed temperature) is to sharpen the vapour–liquid interface and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness decreases and the surface tension increases as the molecular chains get longer. The interfacial thickness and surface tension appear to exhibit an asymptotic limiting behaviour for long chains. A similar behaviour is also observed for the coexistence densities and critical properties. Agreement between theory and simulation results indicates that SAFT-VR DFT is only able to predict qualitatively the interfacial properties of the model. Our results are also compared with simulation data taken from the literature, including the vapour–liquid coexistence densities, vapour pressures, and surface tension.Francisco José Martínez-Ruiz, Felipe J. Blas and A.Ignacio Moreno-Ventas Bravo acknowledge Ministerio de Economía y Competitividad of Spain for financial support from project FIS2013-49620-C2-1-P, co financed with EU Feder funds. We also acknowledge financial support from project number FIS2015-71749-REDT ‘‘Red de Simulación Molecular’’, Acciones de Dinamización Redes de Excelencia del Ministerio de Economía y Competitividad. Additional support from Universidad de Huelva and Junta de Andalucía is also acknowledged

Fotobiorreactor para el cultivo de organismos fotótrofos.

Un fotobiorreactor para el cultivo de organismos fotótrofos, que comprende un depósito que a su vez comprende un medio de cultivo y biomasa en el interior de dicho depósito y en contacto con dicho medio de cultivo. El fotobiorreactor comprende además al menos una estructura cónica o troncocónica transparente o translúcida situada total o parcialmente en el interior de dicho depósito a través de la cual o las cuales una radiación luminosa penetra en dicho depósito.Solicitud: 201001463 (11.11.2010)Nº Pub. de Solicitud: ES2356653A1 (12.04.2011)Nº de Patente: ES2356653B2 (20.02.2012)Corrección: ES2356653B8 (22.03.2012

Copper Flash Smelting Process Balance Modeling

Process control in flash smelting is based on mass and energy balance from which the operational parameters (oxygen coefficient, oxygen enrichment, and flux demand) are obtained to achieve matte and slag with defined compositions and at defined temperatures. Mineral compositions of copper concentrates, and their blends, have been used in order to optimize the heat process balance. The classical balance methodology has been improved by using equations for molecular ratios and distribution coefficients that have been calculated using FactSage™. This paper describes the development of balance equations and compares their theoretical (equilibrium) results with industrial data logs of the smelting process

Composition of biotites from the cortlandites of the Sierra de Gredos, Spanish Central System

Biotites from cortlanditic rocks of the Sierra de Gredos (Central System) were analyzed with the microprobe. The first results of this study are presented here. These include a brief discussion about the dominant coupled substitutions as a method to calculate the ferric iron in the molecula- The studied micas are phlogopites in which the cation substitutions are dominated by Ti and A

Calcic amphiboles from the cortlandites of Sierra de Gredos, Spanish Central System

Calcic amphibo[es from cortlanditic rocks of the Sierra de Gredos were analized with the aim of knowing chemical controls and crystallization conditions. These amphiboles constitute part of the intercumular skeleton. They are rich in alumiina implying mínimum crystal/ization pressures of about 10 for near solidus temperatures. These conditions are diferent from that deduced from the composition of amphiboles in the associated gabbros, suggesting a complex history of crystallization and differentiation at diferent crustal level