The bioleaching of low-grade copper sulfide ore and the selective extraction of copper were investigated. Lix984 dissolved in kerosene was used as extractant. The results show that it is possible to selectively leach copper from the ores by heap leaching. The copper concentration of leaching liquor after 250 d is 2.17 g/L, and the copper concentration is 0.27 g/L after solvent extraction. The leach liquor was subjected to solvent extraction, scrubbing and selective stripping for the enrichment of copper and the removal of impurities. The pregnant copper sulfate solution produced from the stripping cycle is suitable for copper electro-winning.

A native mesophilic iron-oxidizing bacterium, Acidithiobacillus ferrooxidans, has been isolated (30 ℃) from a typical, lead-zinc concentrate of Dachang Mine in the region of Liuzhou located in the southwest of China. Two typical copper sulfide minerals, chalcopyrite and bornite, were from Meizhou Copper Mine in the region of Guangdong Province, China. Variation of pH and cell growth on time and effects of some factors such as temperature, inoculation cell number, and pulp density on the bioleaching of chalcopyrite and bornite were investigated. The results obtained from the bioleaching experiments indicate that the efficiency of copper extraction depends on all of the mentioned variables, especially the pulp density has more effect than the other factors on the microorganism. In addition, the results show that the maximum copper recovery was achieved using a mesophilic culture. The copper dissolution reached 51.34% for the chalcopyrite while it was 72.35% for the bornite at pH 2.0, initial Fe(Ⅱ) concentration 9 g/L and pulp density 5%, after 30 d.

Based on a process design idea, investigations at Technical University of Berlin confirm that the biocoagulation of microorganisms and solid particles would be a new method to generate coarser particles suitable for sorting. The procedure of selective biocoagulation of microorganisms, e.g. yeasts like Saccharomyces cerevisiae and Yarrowia lipolytica respectively, and micro-dispersed solids, e.g. minerals like galena and sphalerite, has been analyzed as a basis for a novel sorting process. Therefore, especially the characteristics of the cell surface of the microorganisms, e.g. the electrostatic charge and the composition of extracellular polymeric substances, as well as their influence on the selective biocoagulation were studied. Experimental investigations show that the microorganisms and the sulphide particles below 10 µm coagulate effectively. Furthermore, the flotation is suitable for the separation of the selectively formed biocoagulates. With the designed column flotation, satisfying recovery rates are reached.

Jinchuan low grade nickel (0.4%−0.6% Ni, mass fraction) sulfide mineral ore contains a remarkably high content of magnesia (30%−35% MgO, mass fraction) present in the main gangue minerals. Bioleaching was performed to investigate the feasibility to process the mineral due to its relative simplicity, eco-friendly operation and low capital cost requirements. The mixed mesophiles were enriched from acid mine drainage samples collected from several acid mines in China. Considering that the magnesia is easily extracted by acid solution and the excessive Mg²⁺ will exceed the tolerance of the mixed mesophiles, three effective means were used to reduce the disadvantage of magnesia during the bioleaching operation. They were adaptation of the mixed mesophiles to improve the tolerance; pre-leaching to remove most leachable magnesia and periodic bleeds of a portion of the pregnant leaching solution to control the level of Mg²⁺ based on the tolerance of the mixed mesophiles. An extraction of nickel (90.3%) and cobalt (88.6%) was successfully achieved within a 300 d leaching process from the Jinchuan low grade nickel sulfide mineral ore using a column reactor at ambient temperature.

Bioshale project, co-funded by the European Commission (FP6 programme), started in October 2004 and finished in October 2007. The main objective of this project was to define innovative biotechnological processes for ”eco-efficient” exploitation of black shale ores. The black shale ores contain base, precious and high-tech metals but also high contents of organic matter that handicap metal recovery by conventional techniques. Three world class black shale deposits were chosen as targets of the R&D actions. These include one deposit that existed under natural conditions (Talvivaara, Finland), one currently in process (Lubin, Poland) and one after mining (Mansfeld, Germany). The main technical aspects of the work plan can be summarized as follows: evaluation of the geological resources and selection of metal-bearing components; selection of biological consortia to be tested for metal recovery; assessment of bioprocessing routes, including hydrometallurgical processing for metals recovery; techno-economic evaluation of new processes including social and environmental impacts. An overview of the main results obtained by the 13 European partners (from 8 countries) involved in this completed research programme is given in this work.

The bioleaching of chalcopyrite in shake flasks was investigated by using pure Acidithiobacillus ferrooxidans and mixed culture isolated from the acid mine drainage in Yushui and Dabaoshan Copper Mine in China, marked as YS and DB, respectively. The mixed culture consisted mainly of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptospirillum spp. (Leptospirillum ferriphilum and Leptospirillum ferrooxians). The results show that the mixed culture is more efficient than the pure Acidithiobacillus ferrooxidans because of the presence of the sulfur-oxidizing cultures that positively increase the dissolution rate and the recovery of copper from chalcopyrite. The pH value decreases with the decrease of chalcopyrite leaching rate, because of the formation of jarosite as a passivation layer on the mineral surface during bioleaching. In the bioleaching using the mixed culture, low pH is got from the sulfur oxidizing inhibiting, the formation of jarosite. The copper extraction reaches 46.27% in mixed culture and 30.37% in pure Acidithiobacillus ferrooxidans after leaching for 75 d.

Extractive operations usually co-produce large quantities of unmarketable materials (mineral wastes), most of which are conventionally discarded to dumps (coarse material) and tailings ponds (fines). Escalating cost and regulation worldwide highlight an increasing need for reduction and re-use of such wastes. The present paper introduces a new integrated waste management scheme for solids and water. The scheme was exemplified by novel treatment of synthetic waste and process water linked to the biohydrometallurgical processing of metal sulphide flotation concentrates. Bioleaching of sulphide concentrate leads to two types of solid waste: a ferrihydrite/gypsum precipitate from neutralisation of the bioleach liquor and un-leached gangue. The paper indicates that, depending upon the minor components involved, the solid phases in admixture might be usefully distributed among three types of product: conventional underground backfill, cemented civil engineering backfill (particularly controlled low strength material or CLSM) and manufactured soil. It emphasizes CLSM containing simulated mineral waste, showing that such material can exhibit the required characteristics of strength, porosity and permeability. When toxic components, e.g., arsenic from refractory gold ore, are present, encapsulation will be required. Process water is typically recycled as far as possible, although any excess should be treated before re-use or discharge. The paper also highlights treatment by reverse osmosis (one of the few methods able to generally remove dissolved components), particularly showing that arsenic in oxidation state +6 can be readily removed for discharge (＜50×10⁻¹² As), although additional ion exchange is needed for potable water (＜10×10⁻¹² As).

The microbial community structure in the ore surface of Zijinshan commercial low-grade copper bioleaching heap was investigated by 16S rRNA gene clone library. For both bacteria and Archaea, 105 clones were sequenced. The dominant bacteria species present in the ore surface were Acidithiobacillus and Leptospirillum, accounting for 51.42% and 48.57%, respectively. However, for the Archaea, only one operational taxonomic unit (OUT) belonged to Ferroplasma acidiphilum. These results indicate that function of genus Acidithiobacillus in the commercial low-grade copper bioleaching heap may be underestimated. More detailed and quantitative information on microbial community structure over time are now under investigation.

A leaching process for base metals recovery often generates considerable amounts of impurities such as iron and arsenic into the solution. It is a challenge to separate the non-valuable metals into manageable and stable waste products for final disposal, without loosing the valuable constituents. Boliden Mineral AB has patented a two-stage precipitation process that gives a very clean iron-arsenic precipitate by a minimum of coprecipitation of base metals. The obtained product shows to have good sedimentation and filtration properties, which makes it easy to recover the iron-arsenic depleted solution by filtration and washing of the precipitate. Continuos bench scale tests have been done, showing the excellent results achieved by the two-stage precipitation process.

The effect of Cu²⁺ ions on bioleaching of marmatite was investigated through shake leaching experiments. The bacteria inoculated are a mixed culture of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Lepthospirillum ferrooxidans. The results show that zinc is selectively leached, and the addition of appropriate content of Cu²⁺ ions has positive effect on the bioleaching of marmatite. SEM and EDX analyses of the leaching residue reveal that a product layer composed of iron sulfide, elemental sulfur and jarosite forms on the mineral surface. The biooxidation of elemental sulfur is catalyzed by the Cu²⁺ ions, which eliminate the barrier to bioleaching of marmatite and keep low pH value. With the addition of 0.5 g/L Cu²⁺ ions, the maximum zinc extraction rate reaches 73% after 23 d at the temperature of 30 ℃ with the pulp density of 10%, while that of iron is only about 10%.

The cross-sectional images of nine groups of ore samples were obtained by X-ray computed tomography(CT) scanner. Based on CT image analysis, the fractal dimensions of solid matrix, pore space and matrix/pore interface of each sample were measured by using box counting method. The correlation of the three fractal dimensions with particle size, porosity, and seepage coefficient was investigated. The results show that for all images of these samples, the matrix phase has the highest dimension, followed by the pore phase, and the dimension of matrix-pore interface has the smallest value; the dimensions of matrix phase and matrix-pore interface are negatively and linearly correlated with porosity while the dimension of pore phase relates positively and linearly with porosity; the fractal dimension of matrix-pore interface relates negatively and linearly with seepage coefficient. Larger fractal dimension of matrix/pore interface indicates more irregular complicated channels for solution flow, resulting in low permeability.

In the case of in-situ leaching of uranium, the primitive geochemical environment for groundwater is changed since leachant is injected into the water bearing uranium deposit. This increases the concentration of SO₄²⁻, uranium and other heavy metal ions and results in the groundwater contamination. The effects of pH values of the simulated solution on the reduction of SO₄²⁻ and the removal of uranium and other heavy metal ions by sulfate reducing bacteria(SRB) were studied. The results show that, when the pH value of the simulated solution is about 8, the reduction rate of SO₄²⁻ by SRB and the removal rate of uranium, Mn²⁺, Zn²⁺, Pb²⁺ and Fe²⁺ will reach their highest values. A bioremediation technique for remediation of groundwater in in-situ leaching uranium mine can be developed.