(198n) Comprehensive Thermodynamic Modeling of Mixed-Solvent Electrolyte Systems: An Investigation on the Quaternary System of FeCl2-FeCl3-HCl-H2o

To treat and remove phosphorus from wastewater, the primary method has been through iron salts, such as ferrous and ferric chloride [1, 2] which are also present in leaching of chalcopyrite and etching of nickel-lead frame [3, 4]. Moreover, iron species exist in the electronic waste (e-waste) associated with computer and cell phones which requires treatment before disposal [5]. In this context, a rigorous, accurate, and widely applicable thermodynamic model is developed to describe the vapor-liquid equilibria (VLE) and solid-liquid equilibria (SLE) behaviors of FeCl₂ and FeCl₃ in water, as well as in the binary mixed-solvents of HCl-H₂O. The model is based on eNRTL equation, with a set of chemical reactions depicting complete dissociation of iron (II) and (III) chloride before saturation, and salt precipitation equilibria with hydrated salt crystals. Furthermore, the mixed-solvent electrolyte systems of FeCl₂-HCl-H₂O, and FeCl₃-HCl-H₂O were thoroughly investigated by directly inheriting molecule-molecule, and molecule-ion interaction parameters of the binary system of HCl-H₂O from previously established model by present authors. By correlating experimental data including mean ionic activity coefficient, osmotic coefficient, enthalpy of formation, heat capacity, and solubility, the model predicts VLE and SLE behaviors, calorimetric properties, and speciation of ternary systems of FeCl₂-HCl-H₂O, FeCl₃-HCl-H₂O, and FeCl₂-FeCl₃-H₂O over the entire concentration range and temperatures up to 400 K successfully. Hence, the model should present the most reliable predictions for the quaternary system of FeCl₂-FeCl_­3-HCl-H₂O.

Keywords:Electrolyte NRTL model, Ferrous Chloride, Ferric Chloride

 

References:

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