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The low-grade copper ore in a high-latitude cold region consists of primary copper sulfide ore, secondary copper sulfide ore, and copper oxide ore. The ore properties gradually change with the depth of the ore body. Under natural temperature, medium temperature, or acidic conditions, tennantite and tetrahedrite in the primary copper sulfide ore, secondary copper sulfide ore, and combined copper oxide ore are easily leached. For shallow low-grade copper ore, sulfuric acid column leaching in atmospheric temperature was conducted at temperatures of 13 °C 23 °C for 34 d, followed by medium-temperature bio-oxidation column leaching with leaching bacteria added at temperatures of -23 °C-30 °C, achieving a copper leaching rate of 65.01%. For medium-deep low-grade copper ore, a pilot test was conducted under conditions of ore particle size 50 mm and a column leaching time of 288 d, achieving a copper leaching rate of 41.66%. [ABSTRACT FROM AUTHOR]

Ore particle segregation commonly occurs during dump leaching because of the differences of particle size, surface roughness, and relative density. The presence of a fine interlayer is key factor of the uneven erosion of the ore surface during leaching, which seriously limits the bioleaching efficiency of copper extraction. To explore the interaction effects of fine interlayers on leaching behavior, the surface morphology and passivation occurrence during the leaching process was studied, where coarse ore particles (4 mm < d < 6 mm) and fine ore particles (2 mm < d < 4 mm) were selected, and a bioleaching experiment of secondary copper sulfide with fine interlayers located at different positions was carried out. Analysis were carried out using computed tomography (CT) scanning technology and field-emission scanning electron microscopy-energy dispersive spectrometry (FE SEM-EDS) technology in the macro, meso, and micro scales. As a result, the macro leaching dynamics, meso-scale ore particle agglomeration, and micro surface morphology characteristics as well as passivation were studied. The results show that fine interlayer leads to a lower copper extraction rate, which is lower than when the fine interlayers are mixed with homogeneous coarse granular medium. The effects of fine interlayers on ore extraction depend on their location. In the experiment, the fine interlayers located at the top results in the highest copper extraction rate (71.3%) after leaching for 60 days; the degrees of evolution of the ore surface pore structure are different at different heights inside the same fine interlayers. The copper extraction rate reaches its peak after leaching for 60 days. The ore particle agglomerations and passivation phenomenon are significant. Passivation layers, such as of jarosite, polysulfide, extracellular polymeric substances, sulfur film, are formed on the ore surface.

Bioleaching is one of the most effective methods of extracting valuable elements from low-grade, refractory secondary copper sulfide. In this research, Acidithiobacillus ferrooxidans was used to leach refractory secondary copper sulfide from Fujian Province. The bioleaching microorganisms were added to the culture, domesticated, and column leaching experiments. These were based on different particle size ratios and carried out sequentially. Based on this experiments, the evolution disciplinarians of bacterial concentration, pH values and copper extraction rates were obtained at different stages. Using computed tomography (CT) technology, ore heap slumping inside the columns, cross section porosity evolution and leaching mechanisms were studied. The results indicate that bacterial concentration and pH values present trends that increase first and then stabilize. The proliferation of bacteria in the leaching columns is slower and the bacterial concentration is only 5×107 per mL after 480 h. During the leaching process, fine particles tend to move to the bottom of columns and the ore heap slump phenomenon appears. On the top surface of the column the porosity tends to be greater with increase rate of 6.65%, conversely, this tends to be smaller at the column bottom, and its decreases rate is 8.29%. The slump degree is proportional to the fines content; the minimum slump is 1.7 mm and the maximum 6.15 mm. Ore particle size is the key factor in the leaching process; column B (with particle size r < 1 mm accounted for 28.41% of whole ores quality) shows the best copper extraction rate of 47.23% after 480 h.

Abstract: This paper discusses a case study on a bioheapleaching system operated commercially at Zijinshan copper plant in China, which applied bioheapleaching–SX (solvent extraction)–EW (electrowinning) to treat a distinct secondary copper sulfide ores. The operating parameters and microbial community structure succession were summarized in this paper, and their correlation with the system characters is studied. Over the four years of industrial operation, fully taking advantages of high acidity, high iron concentration, high salinity and elevated temperature caused by the high content of pyrite (5.8%) within the ore, the growth of iron oxidizers was inhibited and that of sulfur oxidizers were promoted to dominate the heap. Copper was leached efficiently with a recovery of 80%, according to the residue analysis and iron was balanced at low cost by jarosite formation in the heap, using appropriate engineering technologies such as multi-lift permanent stacking in coarse particle size (P80 =40mm), without agglomeration and aeration. The total operation cost was low at 1.10USD/lb at a low copper grade of 0.38%. The case study presented in this paper provides operational data and analysis that would benefit the optimization of similar bioleach plants of secondary copper sulfide. [Copyright &y& Elsevier]

Abstract: Bioleaching, also referred to as minerals biooxidation, and bioremediation have been widely employed commercially for heap and dump bioleaching of secondary copper sulfide ores, sulfidic-refractory gold concentrates and treatment of acid rock drainage. Technical and commercial challenges, identified in this paper, remain for bioleaching of primary sulfides and complex ores. New frontiers for the technology exist in processing massive sulfides, silicate-locked minerals and in the more distant future in-situ leaching. Decommissioning of cyanide heap leach operations and stabilizing mine wastes using biotechnology are opportunities requiring intensive and focused research, development and engineering efforts. [ABSTRACT FROM AUTHOR]