Jarosite and gypsum impacting on bioleaching of copper and nickel sulfide ores

摘要

The presence of potassium, sodium and iron (III) ions in the leaching system led to the formation of jarosite within the ore bed which incorporated some nickel and copper ions into the jarosite precipitate, thereby diminishing the overall recovery of metal value. The experiment results of Cu, Ni and Fe coprecipitation with jarosite formation indicated that copper ions were easier to be incorporated into the jarosite precipitates, and the contents of K and Cu in the jarosite decreased with Fe concentration increasing from 5 g/L to 15 g/L, so, we thought that copper ions were easier to be incorporated into the jarosite than ammoniojarosite. It was more likely nickel ions were absorbed onto the jarosite surface, but it was not clear whether the copper ions were incorporated into sites of the jarosite structure or encapsulated within jarosite aggregate or absorbed onto the jarosite surface. Gypsums were observed within the ore bed although leaching liquors contain calcium at low concentration ( about 500 mg/L). A layer of jarosite or gypsum "scale" on particle surfaces which encapsulated sulfide grains and was of sufficient depth and integrity to have hindered the transfer mass. In addition to the jarosite or gypsum precipitation could reduce the porosity of the heap and change the leaching pathway.