Behavior Of Ions In The Bioleaching Of Low-grade Copper-nickel Sulfide Ore

The ions behavior of copper, nickel, iron(â…¢), potassium, sodium and calcium with the leaching of low-grade nickel-bearing sulfide ore and copper-bearing sulfide ore was investigated.The presence of potassium, sodium and iron(â…¢) ions in the leaching system of the bioleaching of low-grade nickel-bearing and copper-bearing sulfide led to the formation of jarosite within the ore bed which could incorporate nickel and copper ions into the jarosite precipitate, thereby diminishing the overall recovery of metals value.The chemical analysis of the Cu, Ni and Fe co-precipitation further more indicated that some copper ions was incorporated into the jarosite precipitates, but the content of Ni in the jarosite was very low. Therefore, copper ion was believed to be easier to be incorporated into the jarosite precipitates. When the Fe concentration increased from 5 g/L to 15 g/L the content of K in the jarosite decreased from 2.14% to 1.88%, similarly, the content of Cu in the jarosite decreased from 0.16% to 0.10%, so, copper ions was believed to be easier to be incorporated into the jarosite than ammoniojarosite, because when total iron concentrations were 5 g/L the precipitates were mainly jarosite, while total iron concentrations were 15 g/L, the precipitates were mainly ammoniojarosite.Whether column leached low-grade nickel-bearing sulfide ore or copper-bearing sulfide ore, gypsums were observed within the ore bed although calcium concentrations in the leaching solution were about 500 mg/L. The experiment results showed that the solubility of gypsum decreased in the presence of metal sulfate (such as nickel, copper, ferrous and ferric), and even more decreased with increasing metal sulfate concentration or decreasing pH value.A layer of jarosite or gypsum "scale" on particle surface could encapsulate sulfide grains and was of sufficient depth and integrity to have hindered the transfer mass of reaction between the bulk solution and mineral surface. In addition to the jarosite or gypsum precipitation would, even if not coating mineral particles, occur in pore structures so as to reduce the porosity of the heap and change the leaching pathway.The bioleaching of the artificial mixture of copper-bearing sulfide ore with thermophile of Sulfobacillus thermosulfidooxidans and Ferroplasma sp. shown that when the iron ion in the leaching system was the ferrous form that could reduce the formation of jarosite, and did not impact on the leacing of metals value.