Thermodynamic equilibrium models

Nenes A, Pandis SN, Pilinis C (1998) ISORROPIA a new thermodynamic equilibrium model for multiphase multicomponent inorganic aerosols. Aquat Geochem 4 123-152... 

The thermodynamic equilibrium models, including surface complexation models, require the solution of a complex mathematical equation system. For this reason, many computer programs (e.g., CHEAQC, CHEMEQL, CHESS, EQ3/6, F1TEQL, Geochemist s Workbench, H ARPHRQ, JESS, MINTEQ and its versions, NETPATH, PHREEQC, PHRQPITZ, WHAM, etc.) have been developed to calculate the concentration and activity of chemical species, estimate the type and amount of minerals formed or dissolved, and the type and amount of sorbed complexes. 

Deficiencies of Surface Complexation Models Surface complexation models, similar to the other thermodynamic equilibrium models, have some deficiencies. As all models, the equilibrium models simplify the real system. Thus, in the case of geological systems that are very complicated... 

Physico-chemical speciation refers to the various physical and chemical forms in which an element may exist in the system. In oceanic waters, it is difficult to determine chemical species directly. Whereas some individual species can be analysed, others can only be inferred from thermodynamic equilibrium models as exemplified by the speciation of carbonic acid in Figure 9. Often an element is fractionated into various forms that behave similarly under a given physical (e.g., filtration) or chemical (e.g., ion exchange) operation. The resulting partition of the element is highly dependent upon the procedure utilised, and so known as operationally defined. In the following discussion, speciation will be exemplified with respect to size distribution, complexation characteristics, redox behaviour and methylation reactions. 

Modelling calculations were performed for Crooks Gap and Bonanza to determine how much calcite could dissolve given sufficient time to reach equilibrium between calcite and the added CO2. The purpose of the calculations was to determine how far from equilibrium the natural systems were, and to assess the potential for using a thermodynamic equilibrium modelling program to predict well bore scale (discussed in the next section). 

The Larimer-Grossman condensation model has received its share of criticism in the intervening decade. Much of the debate was raised by the assumption that all solid and gaseous species fully equilibrated, which seems unlikely, particularly at lower temperatures. Despite these concerns, the equilibrium picture fits many of the broad scale chemical features of our solar system remarkably well. It certainly demonstrates the power of thermodynamic equilibrium models, considering the size and complexity of the chemical system that is our niche in the universe. 

Denn (20) discusses a similar case for coal gasifiers, where the kinetic-free model (thermodynamic equilibrium model) fails in certain regions of parameters, necessitating the use of a kinetic model. 

In order to improve our understanding of the speciation of mercuiy in FGD gypsum, the authors have used thermodynamic equilibrium models in order to predict the composition of the chemical species in gas phase using the HSC-Chemistry 5.0 software. The theoretical study was carried out in the same conditions that the experimental study, at atmospheric pressure and temperatures ranging between 25 and 800 C. HSC-Chemistiy program uses data base with enthalpy, entropy and calorific capacity values for more than 15000 species. This software allows modify the quantity of different species implicated in the reaction and the program determines tlie products formed, theoretically, in the equilibrium. 

Juang, R.-S., Kao, H.-C. Wu, W.-H. (2004). Analysis of liquid membrane extraction of binary Zn(It) and Cd(ll) from chloride media with Aliquat 336 based on thermodynamic equilibrium models. Journal of Membrane Science, 228, 2, 169-177, ISSN 0376-7388... 

Jarungthammachote, S., Dutta, A. 2007. Thermodynamic equilibrium model and second law analysis of a downdraft waste gasifier. Energy 32 1660-1669. 

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