Stability Diagrams for Copper-Sulfide and Copper-Recycle Systems Applied to Extractive Metallurgical Processes

Abstract

Copper porphyry the world and very of copper, silver and gold. These deposits initially consist of disseminated sulfide minerals in a rock matrix, but near-surface weathering oxidizes the sul fi des and dissolves metals from the residual mass. These leached metals in solution percolate downward and are often reprecipitated in an enrichment zone overlying unreacted sulfide protore. The near-surface weathered, oxidized portion of the deposit corresponds to the oxidized region (high oxidation potential), while the non-oxidizing reduced enrichment zone corresponds to the reduced Copper sul fi de from ore deposits and recycled copper from collected wastes are the two main resources for the production of copper metal. Thermodynamic calculations can be used to serve as a guide for characterization of ore deposits and their mineralogy as well as for process development by mineral processing and by waste separation. The concentrated ore and separated waste can then be processed by pyro- and/or by hydro-metallurgical operations. Such operations may be controlled by oxidation-reduction potential, temperature, complexing reagents (gas, solid or dissolved species), oxidant- reductant, and mass of components. Commonly used stab ility diagrams for aqueous system include speciation (counting alpha) and E H -pH (Pourbaix) diagrams and, for non-aqueous systems, are partial pressure (Kellogg), binary and ternary phase, and Ellingham diagrams. For multicomponent systems, the appropriate approach for the construction of the stability diagram is to use a complete mass balance approach rather than draw the equilibrium line between two adjacent species. Not limited to two variables, a three- dimensional diagram can also be constructed. This paper illustrates the use of stability diagrams for investigating and interpreting how operation variables are important with a focus on extractive metallurgical operations to produce copper. Industria l operation conditions are marked on the diagrams.