Mechanism of chalcopyrite formation from iron monosulphides in aqueous solutions (< 100°C, pH 2–4.5)

Chalcopyrite formation through the metathesis of pyrrhotite with aqueous copper

“…3B based on the ideal surface area of tablet. The aims of this experiment were to evaluate the heterogeneity of copper-pyrrhotite reactions across the surface, as reported by Chang et al (1954), and to develop further the mechanism of chalcopyrite formation by the metathesis of pyrrhotite with copper ions, as proposed by Cowper and Rickard (1989).…”

“…Previously Cowper and Rickard (1989) proposed that the mechanism of pyrrhotite metathesis with aqueous copper to form chalcopyrite involved three key intermediate composition regions described as phases A and B and a cubanite-like phase and that each of the intermediates occupied a region several microns in depth. In the present study, the finely ground pyrrhotite underwent extensive alteration when treated with copper ions (see electronic annex).…”

“…A temperature of 80°C was chosen for study for the convenience of significant recovery with short experimental duration. The selected temperature is at the upper end of the 20-80°C range employed by Cowper and Rickard (1989) to measure the kinetics of the reaction between pyrrhotite and cupric sulfate solution. After 24 h of treatment, bottles were taken out of the oven and prepared in one of two ways; (i) slurry was syringed through 0.2 lm Supor-Acrodisc Ò membrane filter and liquid collected for ICP-OES analysis, or (ii) slurry was vacuum-filtered through a 0.2 lm Supor Ò 200 membrane and washed with 200 mL of deionised water in 25 mL batches; the solid was then dried in a vacuum desiccator prior to analysis (X-ray diffraction and QEMSCAN Ò ).…”

“…Chang et al (1954) observed that surface products formed on a polished pyrrhotite surface following treatment with cupric chloride solution varied across the exposed pyrrhotite grains and suggested a preferential reaction between copper along certain crystallographic directions. Cowper and Rickard (1989) demonstrated that chalcopyrite did not nucleate directly from solution and, having failed to produce chalcopyrite from copper sulfides and iron solutions, they concluded that "the reaction between solid iron sulfides and dissolved Cu species is the predominant, if not exclusive, route for chalcopyrite formation" below 100°C at pH > 2.9. When polished pyrrhotite sections were reacted with cupric sulfate solution and the composition of the pyrrhotite and surface products examined, it was found that the alteration of pyrrhotite to chalcopyrite was diffusion controlled and passed through a sequence of intermediate-composition transitions which were observed as a copper concentration profile with depth (Cowper and Rickard, 1989).…”

“…Cowper and Rickard (1989) demonstrated that chalcopyrite did not nucleate directly from solution and, having failed to produce chalcopyrite from copper sulfides and iron solutions, they concluded that "the reaction between solid iron sulfides and dissolved Cu species is the predominant, if not exclusive, route for chalcopyrite formation" below 100°C at pH > 2.9. When polished pyrrhotite sections were reacted with cupric sulfate solution and the composition of the pyrrhotite and surface products examined, it was found that the alteration of pyrrhotite to chalcopyrite was diffusion controlled and passed through a sequence of intermediate-composition transitions which were observed as a copper concentration profile with depth (Cowper and Rickard, 1989). This profile was split into three transition phases, the first corresponding to the filling of vacancy sites with copper and the successive phases associated with the exchange of iron(II) with copper(II).…”