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Thermodynamics of CuH2SO4Cl−H2O and CuNH4ClH2O based on predominance-existence diagrams and Pourbaix-type diagrams

1996; Elsevier BV; Volume: 42; Issue: 1 Linguagem: Inglês

10.1016/0304-386x(95)00073-p

1879-1158

Carmen Nila, Ignacio González,

Thermal and Kinetic Analysis

A study of the thermodynamics of the systems copper(II)-sulfuric acid-chloride-water and copper(II)-ammonium chloride-water is presented based on the construction of the corresponding predominance-existence diagrams and Pourbaix-type diagrams. These diagrams, besides elucidating the chemistry of the complexes involved in these systems, predict the optimum experimental conditions and the factors that affect the leaching processes. The existence of a relationship between the predominant species in solution and the species observed at the interface during the electrochemical reduction of copper(II) is established. The predominance of a given species in solution depends on the following conditions: Cl− concentration, in the case of the system Cu(II)H2SO4Cl−H2O, and pH, in the Cu(II)NH4ClH2O system. The predominance of chemical species in solution and the existence of insoluble phases for Cu(II) predicted by the diagrams are corroborated by UV-VIS and X-ray spectra. The Cu(I) species predicted by the diagrams are only corroborated by voltammetric experiments.