Microbial succession during a heap bioleaching cycle of low grade copper sulfides: Does this knowledge mean a real input for industrial process design and control?

The paper Bacterial succession in bioheap leaching ( Brierley, 2001) showed the search for methods to analyze the microbial dynamics in bioleaching industrial processes as a key challenge for advancing commercial bioheap applications. “Chemical and physical conditions within bioheaps change radically from the time the bioheap is stacked and inoculated until bioleaching is completed.” The results from a comprehensive monitoring program by culturing and molecular techniques in an industrial bioleaching process for run-of-mine (ROM) low grade copper sulfide ore in Chile is summarized. The analysis of the compiled information permits an understanding of changes in microbial substrates availability, chemical and physical conditions. A data mining technique, called decision trees was used to analyze the information and to establish rules that represent patterns in the data. The bacterial succession in bioheap leaching solutions allowed the leaching cycle stages to be described as: i) Acid conditioning and soluble copper releasing, ii) Chalcocite Bacterial leaching (ferrous oxidation); iii) Chalcocite Bacterial leaching (ferrous and reduced sulfur compounds — RISC oxidation); iv) Bacterial leaching of sulfide minerals with higher rest potentials (pyrite and covellite), and v) Bacterial oxidation of remnant sulfide minerals and RISC. The impact of other factors on microbiology, such as the solvent-extraction process, aspects of the industrial design and operation are also discussed.

The Research Highlights
► Industrial compiled data of several heaps reveal factors impacting on microbiology.
► The predominance of At.f. vs L.ferriphilum shifts due to heap substrate availability.
► The inventory of solution and mineral substrates in the system seems also relevant.
► Solvent extraction process impact the inoculum potential of raffinate solution.