Thermodynamic analysis of the copper (I) homogeneous and heterogeneous speciation in ammonium thiosulfate leaching systems
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POVAR, Igor; UBALDINI, Stefano; SPINU, Oxana; LUPASCU, Tudor. Thermodynamic analysis of the copper (I) homogeneous and heterogeneous speciation in ammonium thiosulfate leaching systems. In: Canadian Journal of Chemistry. 2019, nr. 9(97), pp. 651-658. ISSN -.
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Canadian Journal of Chemistry
Numărul 9(97) / 2019 / ISSN - /ISSNe 1480-3291

Thermodynamic analysis of the copper (I) homogeneous and heterogeneous speciation in ammonium thiosulfate leaching systems


DOI: 10.1139/cjc-2018-0446
Pag. 651-658

Povar Igor1, Ubaldini Stefano2, Spinu Oxana1, Lupascu Tudor1
 
1 Institute of Chemistry,
2 Institute of Environmental Geology and Geoengineering (IGAG), CNR
 
Disponibil în IBN: 3 octombrie 2019


Rezumat

The paper presents a new thermodynamic approach to studying mixed ligand complex formation reactions in the multi-component two-phase system "cuprous oxide-ammoniacal copper (I) thiosulfate aqueous solution" under real conditions. The quintessence of the developed approach consists in the thermodynamic analysis of concurrent reactions in the heterogeneous system Cu(I)-NH3-S2O32--H2O on the basis of the introduced notion of generalized reaction equations. A detailed thermodynamic analysis in ammonium thiosulfate leaching systems has considered the formation of mixed ligand complex species Cu(OH)i(NH3)j(S2O3)k. The new feature is to focus on the chemical description of the overall process of complex formation consisting of a series of concurrent reactions, where the nature and ratio of the concentrations of chemical species, formed in such reactions, depend on the ratio of the concentrations of the metal Cu+ and ligands, temperature, and other thermodynamic parameters. On the basis of the selected thermodynamic data for involved species, the thermodynamic stability areas of solid phase and the repartition of soluble and insoluble chemical species towards the solution pH and a number of total reagent concentrations in heterogeneous mixtures have been investigated. The diagrams of heterogeneous and homogeneous chemical equilibria are used for the graphical representation of complex equilibria and distribution of soluble and insoluble species in examined systems. The used approach utilizes thermodynamic relationships coupled with original mass balance constraints, where the solid phases are explicitly expressed. The obtained results are useful for optimization of the overall scheme of thiosulfate leaching in gold hydrometallurgy to minimize reagent consumption and maximize gold extraction.

Cuvinte-cheie
Ammonia, Copper(I), Gold leaching, thermodynamics, thiosulfate