Gibbs energy approach for aqueous processes with HF, HNO3, and CO2 ? CaCO3
Chemical thermodynamic calculations were used to represent vapor–liquid equilibria and chemical equilibria for aqueous systems with HF, HNO3, and CO2H2OCaCO3 solutions. The entropy production related to the dissolution reaction of calcite was calculated using multiphase thermodynamics and experiments carried out in this work. Modern simulation methods combined with experiments provide a useful tool for the research and design of new processes as well as evaluating changes in the operational conditions of chemical processes. These methods are used to study metallurgical, pulp, and paper industrial processes that involve the presented aqueous solutions. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1942–1947, 2004
Representation of Excess Properties and Liquid Composition of Aqueous Solutions of the HF+Water System
The electrolyte-NRTL model was used to describe the thermodynamic excess properties and the liquid composition of aqueous hydrofluoric acid solutions for overall HF concentrations ranging from dilute to a molality of 20 mol⋅kg−1. Within the framework of this model, three different mechanisms were tested. The first one considers only the dissociation of HF into H+ and F−. The second mechanism takes into account the dissociation of HF and the chemical reaction for formation of HF2−. The third mechanism considers, in addition to these two chemical reactions, the reaction that leads to formation of the dimer H2F3−. The experimental osmotic coefficients of the HF + H2O system were used to estimate the interaction parameters of this model. The resulting parameters yield an accurate description of the Gibbs-Duhem relation for the three mechanisms. The estimated liquid phase speciation for fluoride in the HF+H2O system is comparable to the experimental values of Braddy et al.
Interaction of Formaldehyde and Tetrahydrofolic Acid and Its Relation to the Enzymic Synthesis of Serine
Interaction of Formaldehyde and Tetrahydrofolic Acid and Its Relation to the Enzymic Synthesis of Serine