Bioleaching of a low grade sphalerite concentrate produced from flotation tailings

In this research work, the zinc extraction was investigated, using bioleaching process from a low grade zinc concentrate which was produced from the accumulated flotation tailings. Zinc content was initially upgraded to 11.97% by flotation process. Bioleaching experiments were designed and carried out by a mixed culture of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Leptospirilium ferrooxidans, as well as a mixed moderate thermophile bacteria in the shake flasks. Effect of two types bacteria, indigenous bacteria accompany by concentrate sample, and added mixture of bacteria were evaluated. The term of indigenous bacteria refers to the bacteria which initially exist in the natural concentrate sample. The results showed that more than 87% and 94% of Zn was dissolved in the bioleaching condition of mesophile and moderate thermophile bacteria, respectively. Comparing bioleaching and leaching tests indicated that mesophile bacteria improved Zn extraction 36%, in which contribution of concentrate indigenous bacteria (test condition of non-inoculation) and added mesophile mixed bacteria were equal to 34% and 66% of that improvement, respectively. In addition, moderate thermophile bacteria improved sphalerite leaching up to 38% in which contribution of concentrate indigenous bacteria and added moderate bacteria were about 50% separately.