Keywords

8.1 History of Biomining in China

The earliest record of biomining activities in China can be traced back to the 6th ~ 7th century BC in the book titled Shan-hai Ching, where it was written that “the LuoShui River flows out and into WeiShui River in SongGuo mountain, which contains significant amounts of copper”. Later on, Liu An, the Huainan King, wrote a book titled Huai Nan Wan Bi Shu in the 2nd century BC and recorded copper extraction from acid mine drainage (AMD): “copper was obtained when iron was put into Baiqing solution”. During the Tang and Song Dynasty (600–960 AD), factories producing copper using hydrometallurgy were established, and annual copper production reached more than 1000 t (Qiu and Liu 2019). During the Song Dynasty (960–1279 AD) the pioneering hydrometallurgist Qian Zhang wrote a book Synopsis of Copper Leaching to introduce the copper extraction by hydrometallurgy (Golas 1995).

The first laboratory focusing on biohydrometallurgy in China was built by Professor Fuxu He in Central South Institute of Mining and Metallurgy (now Central South University, CSU, Changsha, China) in 1958. Characterisation of bioleaching microorganisms and bioleaching of metal ores were started in China at that time. In 1960, industrial applications were conducted at the Tongguanshan Copper Mine (Tongling, Anhui, China) by the Institute of Microbiology of Chinese Academy of Sciences (CAS). Bioleaching technology was subsequently applied in a demonstration plant to extract uranium from a low-grade uranium ore heap comprising 700 t of ore. In 1995, CSU exploited and tested copper extraction from low-grade copper ore wastes by biomining at the Dexing Copper Mine, Jiangxi Province. Two years later, a bioleaching plant with an annual production of 2000 t of cathode copper was successfully established at the mine (Fig. 8.1).

Fig. 8.1
Photographs of a biomining plant indicating copper heaps, the pregnant solution in water used, and a small building structure near the water; and the S X - E W plant where small buildings line up the street.

The biomining plant set in 1997 in Dexing Copper Mine, Jiangxi Province, China

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In 1999, the group headed by Prof. Guanzhou Qiu (CSU) started to cooperate with the Oak Ridge National Laboratory (USA) to carry out ecological and genomic research of bioleaching microorganisms, initiating the era of genomic studies in the field of biomining in China. In 2000, the first pilot-scale plant for biooxidative pre-treatment of refractory gold ore with annual treatment of 50 t gold concentrate was officially launched. In 2005, a biomining plant with a capacity of 30,000 t of cathode copper was built in Zijin Mining Company, and the cathode copper purity reached LME grade A.

Currently, the main research activities on biomining in China are performed in CSU, GRINM GROUP (formerly known as General Research Institute for Nonferrous Metals), Institute of Process Engineering of CAS, Institute of Microbiology of CAS, Institute of Oceanology of CAS, Shandong University, Changchun Gold Research Institute, Beijing Research Institute of Chemical Engineering and Metallurgy of China, Northeastern University, University of Science and Technology Beijing, Kunming University of Science and Technology, East China University of Technology, University of South China, and Jiangnan University, etc. The research carried out on bioleaching includes mainly three aspects: (i) microbiology of bioleaching (Guo et al. 2013; Wang et al. 2016; Zhang et al. 2010); (ii) microbial–mineral interactions (Li et al. 2020; Xia et al. 2020; Yu et al. 2018; Yin et al. 2020); (iii) multiple factors that strongly influence bioleaching efficiency (Feng et al. 2021; Gan et al. 2019; Hao et al. 2021; Huang et al. 2022; Liu et al. 2016; Qiu et al. 2011; Ruan et al. 2006; Shang et al. 2021; Wang et al. 2018). The Chinese government has given major financial support for fundamental research and application of biohydrometallurgy, and has established a number of national science and technology plans, including “National Basic Research Program of China (973 Program)”, “National High Technology Research and Development Program (863 Program)”, and “National High Technology Industrialisation Demonstration Project.” The National Natural Science Foundation of China (NSFC) has also provided funding (approximately 1 billion Yuan; approx. $155 M USD). For instance, the number of approved projects in its Engineering and Materials Department increased from 10 in 2000 to 50 in 2010, and the total budget increased tenfold.

8.2 Biomining Development in China

8.2.1 Macroscopic to Microscopic Views of Biohydrometallurgy

In China, the early research in biohydrometallurgy focused mainly on the macro level. Metallurgists often used acid mine drainage (AMD) for improving the bioleaching efficiency of metal ores, without knowing how the bioleaching process worked. Since the discovery of bacteria associated with AMD in 1947 by Colmer et al. (Colmer et al. 1950; Temple and Colmer 1951), microbiologists started to search for, isolate and select strains of microorganisms that were more effective in biomining applications. In 2004, CSU participated in whole genome sequencing of the type strain of Acidithiobacillus ferrooxidans, which was the first sequencing of a biomining microorganism. Based on the data, a national standard (GB/T 20929—2007) entitled “Methods for the detection of At. ferrooxidans and its oxidation activity by microarray” was established by CSU. The establishment of a national standard enabled rapid and accurate screening of bioleaching microorganisms with high iron- and/or sulfur-oxidising abilities. The full map and annotation of the genome of At. ferrooxidans laid the foundation for studying bioleaching mechanisms at the molecular level and realising the orientation of microbial leaching research from phenotypic to genotypic level. In Shandong University, extensive activities on genetic modification of biomining microorganisms for understanding iron and sulfur metabolisms in acidophiles, and improvement of biomining efficacy have been ongoing (Li et al. 2010; Hao et al. 2012; Gao et al. 2020).

8.2.2 From Qualitative to Quantitative Analysis

Biomining microorganisms usually comprise acidophiles which perform iron and/or sulfur oxidation activities (Johnson 2014). It is essential to find a way to quantitatively analyse microbial composition and function for the clarification of multifactors influencing bioleaching efficiency. With the rapid development of molecular methods, genetic, genomic, and metagenomic technologies are increasingly being applied in biomining applications. In particular, the application of genomics has led to significant progress in quantitative analysis of bioleaching systems, such as community structure and function. The development of microbial functional gene array and community genomic array technologies has led the research level from single function of a single population to whole functions of a single population and whole functions of a microbial community. Based on these technologies, the dynamics of microbial community structures and leaching functions can be detected quantitatively and may be used to analyse the effect of leaching parameters on microbial growth and iron-/sulfur-oxidation ability. The established microbial function gene array developed in CSU was used to study the microbial structure and function, allowing the simultaneous detection of the microbial community structure and function in bioleaching system. Based on results from studying the succession mechanism of bioleaching microbial community structure and function, the microbial consortium was optimised through combining different species and strains of microorganisms. The new optimised consortium was successfully applied for the bioleaching of low-grade copper sulfide at the YuShui Copper Mine, Guangdong Province, leading to enhanced levels of copper extraction and recovery.

8.2.3 From Theory to Practice

8.2.3.1 Biomining of Copper Ores

China is currently the top global consumer of copper, but its present domestic production accounts for only about 20% of its copper demand. Biomining technologies facilitate the exploitation of low-grade copper resources in China as elsewhere and can be therefore enhance global copper production. Below, several biomining industry applications for copper production are listed and described.

  1. (1)

    Dexing Copper Mine

The heap bioleaching plant in Dexing Copper Mine is an example of a successful application of biomining technology. More than 3.5 Gt of waste ores have been produced during the life of the mine. These contain 0.05%–0.25% (by wt.) copper, so there are approximately 600,000 t of residual copper metal in this material. Since the waste ores are mainly composed of primary copper sulfides such as chalcopyrite, it has proved difficult to obtain high leaching rate using conventional biomining. In order to improve bioprocessing of the Dexing copper waste ores, two research projects “Studies on bioleaching of low-grade sulfide ore with selected bacterial consortium” and “Studies on the catalytic mechanism and strengthening bioleaching strains isolated from Dexing copper mine, and their industrial application” were carried out. Using the quantitative analysis technology developed by CSU, strains of Acidithiobacillus spp. and Leptospirillum spp. and other biomining prokaryotes, with high growth rate, high oxidation ability, and high resistance to metal ions were obtained by microarray screening and used to improve copper extraction. Copper recovery was further enhanced by upgrading the SX-EW plant at the mine (Fig. 8.1).

  1. (2)

    Zijinshan copper mine

The Zijinshan copper mine was the first example of a successful industrial application of biomining in China. This mine is located in Shanghang County (a subtropical region) in Fujian province, and the copper sulfide deposit contains 240 Mt. of ore averaging 0.063% copper. Chalcocite and covellite are the copper minerals comprising the secondary sulfides. Since the copper grade is very low and the deposit contains significant amounts of arsenic, the traditional flotation and smelting process cannot be applied to extract copper economically and effectively, and in 1998 the mine operators began extracting copper using heap bioleaching (Ruan et al. 2006). Due to the relatively warm climate (average atmospheric temperature at the mine is 16–20 °C), heap bioleaching is favourable. Several steps, from shake flask tests to column tests and pilot tests combined with solvent extraction-electrowinning (SX-EW), were initially trialled to improve microbial efficacy and copper recovery. Not surprisingly, Acidithiobacillus spp. and Leptospirillum spp. appeared to be the dominant leaching organisms in the bioleaching process (Yin et al. 2018; Chen et al. 2020). From these early experimental studies (Fig. 8.2), the Zijinshan Copper Mine established a heap bioleaching factory with an ore processing rate of 60 Mt. y−1 and an annual cathode copper production of 10 Mt. The exploitable copper reserves have increased from 2.7 to 3.1 Mt. by using biomining technology. The copper recovery for heap bioleaching reaches 80% in a leaching period of approximately 200 days.

Fig. 8.2
Three photographs of the Zijinshan Copper mine, where industry applications of heap bioleaching of low-grade copper ore were done. The photos are dated 1998, 2003, and 2006 and correspond to 50,000, 3,00,000, and 33,00,000 tons ore per year.

Heap bioleaching industrial application in Zijinshan Copper mine, Fujian Province, China

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  1. (3)

    Chambishi Copper Mine (Zambia)

Biomining technology developed in China was used to extract and recover copper in Zambia. In 2010, a strategic framework agreement was signed between the Zambian Ministry of Mines and Minerals Development and CSU. Based on the agreement, the “China Nonferrous Metal Mining (Group) Co., LTD—CSU—Zambia biohydrometallurgy technology industrialisation demonstration base” was established. Chambishi Copper Mine contains ~7 million tons of copper, with the chief copper minerals in the ore being bornite and chalcocite, with minor amounts of chalcopyrite. In March 2011, the Zambia Chambishi Copper Company cooperated with CSU to exploit the low-grade copper ore in Chambishi by heap bioleaching. Firstly, the indigenous microorganisms were screened, enriched, and adapted to the heap environment. Then, the adapted microorganisms were sub-cultured in 10 L, 70 L, 2 m3, 28 m3, and 150 m3 stirred tank reactors, successively (Fig. 8.3). The microbial consortium was inoculated into ore heap by irrigation and spraying. The cell numbers were maintained at approx. 108 cells/mL in the leachate liquors. In the heap bioleaching of 600,000 t of low-grade copper ore, copper extraction reached up to 50% in 2 months. Bioleaching solution was processed using SX-EW, producing cathode copper at a rate greater than 10,000 t y−1. Biomining technology was estimated to increase copper recovery by 20%, and to reduce acid consumption by at least 35%, compared to the acid leaching process using sulfuric acid. This was a clear demonstration of how low-grade copper resources can be exploited by using biomining technology.

Fig. 8.3
Photographs of a 150-milliliter shake flask, four 10-liter stirred buckets lined up, six 70-liter stirred buckets being overseen by a technician, a 2 cubic meter stirred reactor, a 28 cubic meter stirred reactor, and a 150 cubic meter stirred reactor with technicians and workers standing near it.

Scale up of the adaption process of bioleaching microorganisms from shake flasks to 150 m3 stirred reactors

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8.2.3.2 Biomining of Uranium Ores

In order to keep pace with the increasing demand of uranium for nuclear power generation, China’s uranium production has been oriented to the exploitation of low-grade or refractory uranium ore, and other mineral resources associated with the processing of uranium. During (indirect) bioleaching of uranium ore, U(IV) is oxidised to U(VI) by ferric iron which is regenerated by iron-oxidising acidophiles, thereby maintaining the leaching reaction. In terms of uranium resources, biohydrometallurgy can enable an efficient use of a large number of idle or abandoned uranium sulfide resources in China and is expected to become increasingly important with projected decline in the grade of uranium resources from 0.1% to 0.03%. Bioprocessing has the potential to significantly lower the cut-off grade of uranium ores and thereby increase the economic mining exploitation of low-grade uranium deposits.

The Institute of Microbiology of CAS started biomining technology for uranium recovery, in the 1970s, with a pilot-scale study of heap leaching was conducted in Uranium Mine 711, (Hunan province). A total of 2 t concentrated uranium was enriched from the surface ore containing 0.02% ~ 0.03% of uranium by biomining for 8 years in the Bofang Copper Mine, Hengyang, Hunan province. In the 1980s, heap biomining of uranium gained rapid development and was applied at the Chaotaobei Uranium Mine (Ganzhou, Jiangxi province), a uranium mine in Xinjiang province and Xiangshan Uranium Mine (Jiangxi province). Using the optimised mixed culture in heap leaching at Fuzhou 721 mine in Jiangxi province, up to 96.8% extraction of uranium was achieved in 97 days.

Most of the examples cited are pilot-scale tests. The promotion and application of biohydrometallurgy could make a large number of idle or abandoned uranium sulfide resources available in China. It is anticipated that biomining can improve the exploitable uranium grade from the current limit of 0.1% to 0.03%.

8.2.3.3 Biomining for the Pre-treatment of Gold Ores

Refractory gold deposits are considered to account for about two-thirds of known global gold reserves, but these are not readily processed using conventional technologies. Biooxidation, however, can be used as a pre-treatment of refractory gold ores, allowing the previous metal to be accessed and solubilised by lixiviants such as cyanide (Chap. 4). China has become the world’s largest producer of gold (Fig. 8.4) and incorporating biooxidation technology for refractory deposits will help to keep China at the forefront of global gold production.

Fig. 8.4
A vertical bar graph. Y-axis denotes gold production per ton, ranging from 0 to 500, in increments of 100. The x-axis denotes years from 2007 to 2020, in increments of 1. From 2007, the bars are at 270.491, 282.007, 313.98, 340.876, 360.975, 403.047, 428.163, 451.799, 450.05, 453.47, 426.14, 401.19, 380.23, and 365.34. A line connects these points.

Gold production in China from 2007 to 2020

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The Shaanxi Provincial Authority of Land and Mines conducted a pilot-scale study on bioleaching pre-treatment of 2000 t of pyritic gold ore (containing 0.54 g Au t−1) in 1994. Following biooxidation, gold recovery reached 58%. Direct extraction of gold by cyanidation of an arsenic-containing concentrate achieved only 35% gold recovery, whereas this was increased to 93% after 5-day pre-biooxidation. In Xinjiang Province, the Baogutu gold mine used biooxidation pre-treatment and gold leaching reached 92% ~ 97%.

The first biooxidation plant for processing gold ore in China was built at the Zhenyuan Gold Mine, Yunnan province. In 1998, Shaanxi Zhongkuang Technology Co. Ltd. established a biooxidation plant for pre-treatment of gold ore concentrates with a processing capacity of 10 t d−1. In 2001, Tiancheng Gold Co., Ltd. imported the BacTech technology from Australia and built a biooxidation plant with a concentrate processing capacity of 100 t d−1, which is no longer operating. In July, 2000, the construction of the first commercial biooxidation plant started at the Yantai Gold Smelter. The plant went into operation at the end of 2000 (Yang et al. 2002). The China National Gold Group Corporation works on the exploitation of arsenic-refractory gold concentrates at the Tianli Gold Company, Liaoning province, China. They have been extensively working on biooxidation/cyanidation technology and developed the “CCGRI” biotechnology in 2005. The processing capacity reached 150 t d−1. The microorganisms (the “HY series” bacteria) employed in this technology are active at 35–52 °C and tolerate up to 22 g As L−1. The HY bacteria were shown to grow in the presence of gold concentrate with a pulp density of 25–27% and 13–15% arsenic content.

Recently, biooxidation of refractory gold ores has developed rapidly and has reached an internationally advanced level. China has built more than 10 biooxidation-cyanide gold plants and currently has the largest number of biooxidation gold plants worldwide. This biotechnology is estimated to contribute ~8% of gold production in China in the near future.

8.3 Future Perspectives

Biomining technologies have undergone significant development in China, and the application of biomining for metal recovery has been industrialised for copper, uranium, gold, and nickel. However, biomining still needs to overcome some detractions in order to facilitate further expansion. For instance, copper production by biomining accounts for less than 8% of the total copper produced in China. This number is still lower than the estimated global level of 10–20% (Chap. 1). Microbial strains that are more effective in industrial applications (e.g., tolerance to high ore pulp density and/or toxic metals) could lead to improvements, and these may to be enriched and selected from both natural and anthropogenic environments. For instance, heap biomining applications in northern China could benefit from using consortia that contain psychrophilic/psychrotolerant strains that remain active at low temperatures. Fresh water is scarce in many places in China (as in many parts of Chile and Australia) and bioleaching using saline and/or brackish waters would help the expansion of biomining, though this requires salt-tolerant, mineral-degrading acidophiles (Chap. 13).

The vast amount of marine mineral resources, such as polymetallic nodules, marine manganese crusts, and massive sulfide deposits on the seafloor, could help to meet the expanding demand for metals in China and other countries, as could the recovery of base and precious metals from e-wastes (Chap. 14). Biomining technologies can be adapted to process these materials.

Last but not least, the contribution of biomining autotrophs which fix CO2 to the carbon sequestration in a global scale has to be discussed and considered and estimated and this may give additional advantages for the expanding of this green technology in China and the rest of the world, though this carbon sequestration is transient and not likely to be a useful means of carbon sequestration like managed forestry (Chap. 1).