The kinetics of dissolution of covellite in acidified ferric sulphate solutions

Abstract

Pure synthetic CuS disks and high-grade natural covellite were dissolved in acidified ferric sulphate solutions in the temperature range 25 to 95°C. For both materials, the rates were relatively slow and increased during the initial stages of the dissolution, eventually becoming nearly linear. The activation energy, as determined from the initial dissolution rates of the synthetic covellite, was 17.8 ± 2.0 kcal/mole. Microscopic examination of both the natural and the synthetic sulphide revealed that the attack occurred preferentially in certain areas. It was felt that the progressive development of such pits was responsible for the gradual rate increase observed during the initial leaching stage. From 0 to 6% of the leached sulphur reported in the sulphate form. The rate of copper dissolution decreased sharply with increasing ferrous sulphate concentrations in the leaching medium. The rate varied directly with the ferric concentration for initial concentrations below 0.005 M Fe3+ but was insensitive to higher ferric strengths. Natural covellite dissolved at approximately the same rate and with essentially the same temperature dependence as the synthetic material. The rate controlling step for the dissolution of CuS was felt to be a chemical reaction occurring on the surface of the sulphide.

The oxidation of Fe(II) with Cu(II) in acidic sulfate solutions with air at elevated pressures

“…CuS can be leached with ferric sulfate (Fe 2 (SO 4 ) 3 ), an operation encountered in copper ore processing (a/o CuS) (Peacey et al, 2004;Dutrizac and MacDonald, 1974). Copper sulfate, elemental sulfur (S o ), and ferrous sulfate (FeSO 4 ) are produced in this process:…”

Dissolution of CuS Particles with Fe(III) in Acidic Sulfate Solutions

“…The activation energy of E A = 22.0 kJ/mol derived in this study is lower than activation energies reported in previous studies. 6,11,12 It seems plausible that the dissolution reaction in this study was controlled by diffusion.…”

“…This observation is in agreement with Thomas and Ingraham 11 and Dutrizac and MacDonald. 6 Thomas and Ingraham 11 reported that Fe 2+ to Cu 2+ molar ratios did not exceed 2.1:1. Dutrizac and MacDonald 6 reported that Fe 2+ to Cu 2+ molar ratios ranged from 2.07 to 2.53.…”

“…Dutrizac and MacDonald studied the dissolution of synthetic covellite disks and natural covellite in acidic ferric sulfate solutions. Synthetic covellite was prepared from copper foil with elemental sulfur in a vacuum sealed tube at an elevated temperature.…”

“…CuS can be leached with ferric sulfate (Fe 2 (SO 4 ) 3 ), an operation encountered in copper ore processing (CuS). , Copper sulfate, elemental sulfur (S o ), and ferrous sulfate (FeSO 4 ) are produced in the process: …”