Synchrotron Radiation XRD Investigation of the Fine Phase Transformation during Synthetic Chalcocite Acidic Ferric Sulfate Leaching

Abstract

The fine phase transformation process of chalcocite (Cu2S) leaching in acidic ferric sulfate solution was studied by leaching experiments and synchrotron radiation X-ray diffraction (SRXRD) tests. The results showed that the dissolution process of chalcocite was divided into two stages. In the first stage, Cu2S was firstly transformed to Cu5FeS4 and Cu2−xS, then the galvanic effect between Cu5FeS4 and Cu2−xS accelerated the dissolution process of Cu1.8S → Cu1.6S → CuS, and finally Cu5FeS4 was also transformed to CuS. While in the second stage, CuS was transformed to elemental sulfur, which formed the passivation layer and inhibited the leaching of chalcocite. Specifically, Cu5FeS4 was detected during the chalcocite leaching process by SRXRD for the first time. This research is helpful for revealing the detailed leaching process of chalcocite.

Effect of particle size on chalcocite dissolution kinetics in column leaching under controlled Eh and its implications

“…The first stage is the conversion of chalcocite into blue-remaining covellite (CuS) via the formation of a series of intermediate products and is very rapid and controlled by diffusion of ferric ion through liquid film around the particle that was supported by low activation energies (4-25 kJ/mol) (Cheng et al, 1991b;Naderi et al, 2015;. In the second stage, covellite is oxidized to produce cupric ion and more than 90% of the sulfide moiety are transformed to elemental sulphur and the rate is very slow and sensitive to temperature (Schippers et al, 1999;Miki et al, 2011;Fang et al, 2018). The rate-controlling step for the second stage is not fully understood and some previous studies on chalcocite dissolution kinetics adopted the stirred leaching whereas the column leaching can help to simulate the operating parameters for heap leaching.…”