Abstract: Kupferschiefer-type ore represents an important source for base metals and several studies concerning the bioleaching of black shale ores and Cu concentrates have been carried out with focus on various microbial communities and processing parameters. However, the incomplete dissolution of chalcopyrite remains a key issue for copper ore bioleaching improvement and requires further investigations in order to ensure an optimal control of the process for upscaling. Our study clearly showed that bioleaching tests are characterized by two separate phases with a distinct optimal temperature. A distinct effect of the temperature on the copper recovery and the advantage of temperature ramp in order to enhance copper bioleaching and chalcopyrite dissolution were demonstrated.
Abstract: “Deep in situ biomining”, widely considered to be a potentially environmentally-benign and cost effective biotechnology for extracting and recovering base metals from deep-buried base metal deposits, is being developed within the EU Horizon 2020 project “BioMOre”. Data are presented from non-aerated column experiments in which a saline, calcareous copper-rich ore (kupferschiefer) was subjected to a three-stage eaching protocol: (i) with water, to remove soluble salts; (ii) with sulfuric acid, to remove calcareous minerals and other acid-soluble salts; (iii) indirect bioleaching with a microbiologically-generated ferric iron lixiviant. Sequential leaching with water and acid removed ~85% of the chloride prior to bio-processing, while ~13% of the copper present in the ore was leached using sulfuric acid, and a further 39 - 59% by the lixiviant.
Abstract: The first production shop in Russia of refractory gold ores biooxidation using chemoautotrophic microorganisms association was launched in 2001 at Olimpiada gold recovery plant. The shop was designed for treatment of 3 million tons of Olimpiada deposit “Vostochniy” pit primary sulphide ore per year. In 2007 the BIO-2 shop designed for treatment of 5 million tons of primary sulphide ore was launched. Total capacity of the two bio-processing unit is 8 million tons of sulphide ores per year. A more advanced concept of BIO-3 shop was developed based on industrial operation and performance analysis of BIO-1 and BIO-2. The concept was based on biooxidation process automatisation with displaying control and managing parameters of the process on the monitors in control room. This allows to keep main process parameters within the specified limits and maintain process in a stable high-performance state. Installation of the automatisation systems in BIO-1 and BIO-2 shops allowed increasing the throughput of all flotation concentrate treatment shops from 870 t/day to 1200-1300 t/day. This led to production of more than 26 tons of gold in 2016. Currently JSC “Polyus” is copyright holder of patented refractory gold sulphide ores concentrate treatment technology, patented microbial association carrying out the process, and the technology itself is protected by the trademark "BIONORD".
Abstract: The objective of this study is to improve the understanding of copper sulfides dissolution and to use this knowledge for optimization of process parameters for commercial application of electrochemical bioleaching of chalcopyrite concentrates in stirred bioreactors. From the results of this study, the importance of the oxidation reduction potential (ORP) on the catalytic interaction between chalcopyrite and pyrite can be pointed out as the main parameters for successful bioprocessing of chalcopyrite concentrates. Under these conditions, the optimization of the average particle size of feed (D80) and adjusting the ORP in the range between 400-450 mV are important criteria for increasing the electrochemical bioleaching rate of chalcopyrite concentrates. It seems that the main reason for the increased copper recovery could be the control and prevention of chalcopyrite passivation resulting from improved galvanic interaction between copper sulfide minerals, here especially chalcopyrite and pyrite in the selected ORP range and the right particle size distribution of feed. At optimum conditions, the copper extraction from chalcopyrite flotation concentrate during 7 days of continuous electrochemical bioleaching operations in stirred tanks was about 95%, which should be high enough to justify the process economically.
Abstract: Environmentally friendly mining technologies have to be developed extensively to avoid the impact of mining activities with respect to environmental concern. One example of such technology is bioleaching which has been developed worldwide and is regarded as an appropriate technology for the extraction of metals from polymetallic ores such as supergene porphyry copper ores, mainly consisting of secondary copper sulfides, including chalcocite (Cu2S), covellite (CuS), or oxide minerals, i.e., cuprite (Cu2O) and tenorite (CuO). The extraction process for this complex ore generally requires high temperature, high pressure and/or high acid concentration. For the economic extraction of valuable copper from such ores, the bioleaching of supergene porphyry copper ore from Sungai Max in Southeast Sulawesi of Indonesia was investigated in shake-flask experiments at room temperature (28 °C) for 14 days using an iron- and sulfur-oxidizing bacterium (Alicyclobacillus sp.) indigenous to an Indonesian mine site. The main mineralogical composition of gangue minerals contained in this ore sample included quartz, muscovite, kaolinite and alunite. The relatively high copper extraction efficiencies were obtained over a 14-day period of the bioleaching experiments as a function of pH, pulp density and NaCl concentration. Therefore, the findings of this study provide the first information of bioleaching process of supergene porphyry copper ores in Indonesia that may highly be useful for developing an economical and environmentally friendly extraction process of such complex ores.
Abstract: Jarosite is a typical stream of zinc refineries, with high production rates and possible release of metal-contaminated seepage waters during long-term storage in respective disposal sites. Jarosite contains remarkable concentrations of valuable metals, like several weight percentages of zinc and lead, in addition to lower concentrations of copper, silver, germanium, gallium and indium. In this study, jarosite was treated with reductive and oxidative bioleaching for valuable metals recovery. The reductive bioleaching was seen to enhance iron liberation, by transforming the dissolved Fe(III) to Fe(II), while in the oxidative bioleaching iron liberation was lower. Zinc, copper, indium, gallium and germanium dissolution rates were rather identical with both methods. In reactor experiments, the zinc and copper yields were higher than in flask experiments resulting at best in the leaching yield of 35% and 38% for zinc and copper, respectively. Indium and gallium yields were between 5-8%, but approximately 40% of germanium was leached.
Abstract: Mondo Minerals owns talc mines in Finland at Sotkamo and Vuonos. A by-product of their talc mining operations is a high-grade sulfide concentrate containing pyrrhotite, pentlandite, pyrite, gersdorffite and magnesite. Nickel is the main metal of economic interest, but the concentrate also contains a small amount of cobalt and a significant quantity of arsenic. Multiple processing options were evaluated before identifying Mintek’s bioleaching technology as the most suitable for the recovery of nickel and cobalt from this stream. This paper describes the technical development of the process, from laboratory test work to plant design and early plant operation.
Abstract: Since the discovery of bioleaching microorganisms and their role in metal extraction in the 1940s, a number of technical approaches have been developed to enhance microbially catalysed solubilisation of metals from ores, concentrates and waste materials. Biomining has enabled the transformation of uneconomic resources to reserves, and thus help to alleviate the challenges related to continually declining ore grades. The rapid advancement of microbial characterisation methods has vastly increased our understanding of microbial communities in biomining processes. The objective of this paper is to review the recent advances in biomining processes and microbial characterisation.
Abstract: In the commercial BIOX® process, an acidophilic mixed bacterial and archaeal community dominated by iron and sulphur oxidising microorganisms is used to facilitate the recovery of precious metals from refractory gold-bearing sulphidic mineral concentrates. Characterisation of the microbial communities associated with commercial BIOX® reactors from four continents revealed a significant shift in the microbial community structure compared to that of the seed culture, maintained at SGS (South Africa). This has motivated more detailed study of the microbial community dynamics in the process. Microbial speciation of a subset of the BIOX® reactors at Fairview mines (Barberton, South Africa) and two laboratory maintained reactors housed at Centre for Bioprocess Engineering Research, University of Cape Town, has been performed tri-annually for three years by quantitative real-time polymerase chain reaction. The laboratory BIOX® culture maintained on Fairview concentrate was dominated by the desired iron oxidiser, Leptospirillum ferriphilum, and sulphur oxidiser, Acidithiobacillus caldus, when operated under standard BIOX® conditions. Shifts in the microbial community as a result of altered operating conditions were transient and did not result in a loss of the microbial diversity of the BIOX® culture. The community structure of the Fairview mines BIOX® reactor tanks showed archaeal dominance of these communities by organisms such as the iron oxidiser Ferroplasma acidiphilum and a Thermoplasma sp. for the period monitored. Shifts in the microbial community were observed across the monitoring period and mapped to changes in performance of the commercial process plant. Understanding the effect of changes in the plant operating conditions on the BIOX® community structure may assist in providing conditions that support the desired microbial consortium for optimal biooxidation to maximize gold recovery.