Biometallurgy
Biometallurgy means that in the presence of relevant microorganisms, due to the catalytic oxidation of microorganisms, valuable metals in minerals are dissolved into the leachate in ion form for recovery, or A method of dissolving and removing harmful elements from minerals. Many microorganisms can act on minerals through various pathways, converting valuable elements in minerals into ions in solution. Utilizing this property of microorganisms, combined with hydrometallurgy and other related processes, biometallurgical technology has been formed. The main leaching microorganisms include thiobacillus ferrooxidans, thiobacillusthiooxidant, sulfobacillus, ferrobacillus ferrooxi dant, thermoacidophilicarchae bacteri a, and Microspirococcus Genus (1eptospirillum) and so on. In reports on biometallurgy, Thiobacillus ferrooxidans (Thiobacillus ferrooxidans) accounts for the vast majority of papers as the ore-leaching bacteria. However, judging from the researchers’ isolation and culture methods of the ore-leaching bacteria, it should be rich in multiple strains. Collect mixed bacteria. Some of them grow at room temperature, while others can grow at temperatures of 50 to 70°C or higher. During the oxidation process of sulfide ores, ferrous ions, elemental sulfur and related compounds will be produced. Mineral leaching microorganisms are generally chemoautotrophic bacteria. They obtain energy by oxidizing ferrous iron or elemental sulfur and related compounds, and absorb oxygen and Carbon dioxide and absorb metal ions and other required substances in the solution to complete the Kelvin cycle growth.
Dozens of kinds of bacteria used for mineral leaching can be divided into three categories according to their optimal growth temperature, namely mesophilic bacteria, medium thermophilic bacteria and high-temperature bacteria.
The bioleaching process of sulfide ore includes direct and indirect effects of microorganisms, as well as galvanic cell effect and other chemical effects. Direct action means that during the leaching process, microorganisms are adsorbed on the surface of minerals and directly oxidize and decompose sulfide minerals through protein secretions or other metabolites. The indirect effect means that microorganisms oxidize the ferrous ions produced during the oxidation process of sulfide minerals and other ferrous ions present in the leaching system into ferric ions. The ferrous ions produced have a strong oxidizing effect, which further oxidizes the sulfide minerals, and the sulfide minerals are oxidized and precipitated. Valuable metals and iron ions are catalytically oxidized, and so on. According to the configuration status of the ore, there are three main types of biometallurgical industrial production.
(1) Heap leaching method. This method often occupies a large area of ??ground and requires more labor, but it can process a larger amount of ore, ranging from thousands to hundreds of thousands of tons at a time.
(2) Pool immersion method. In the acid-resistant tank, dozens to hundreds of tons of ore powder are piled up. The tank is filled with bacteria-containing leach solution and mechanically stirred to speed up the smelting. Although this method can only process a small amount of ore, it is easy to control.
(3) Underground leaching method. This is a method of leaching metal directly within the deposit. The method is to pour bacterial leaching solution on the mined site and partially exposed ore body, or drill holes in the mining area to the ore layer, inject the bacterial leaching solution through the drill hole, ventilate it, wait for leaching for a period of time, and then pump it out. The leaching solution is used for metal recycling. The advantage of this method is that the ore does not need to be mined or processed, which can save a lot of manpower and material resources and reduce environmental pollution.
The advantages of applying microbial leaching are: mild reaction, environmental friendliness, low energy consumption, short process, especially suitable for lean ore, waste ore, off-surface ore and difficult-to-mine, difficult-to-select, and difficult-to-smelt Heap leaching and in-situ leaching of minerals. Today, when ores are becoming increasingly impoverished and environmental problems are becoming increasingly prominent, microbial leaching technology will be an effective means of metal element extraction, environmental protection and waste utilization. In recent years, foreign research on this technology has become a hot spot in the field of mining and metallurgy. Bacterial leaching has developed into an important mineral processing method. This method can be used to leach copper, lead, zinc, gold, silver, manganese, nickel, and chromium. , molybdenum, cobalt, bismuth, vanadium, selenium, arsenic, cadmium, gallium, uranium and other dozens of precious and rare metals.
The development of biometallurgical research in my country
China is the first country in the world to adopt biometallurgical technology. As early as the 2nd century BC, it was recorded that the use of iron to replace copper sulfate solution The chemistry of copper, heap leaching was a common practice for producing copper at the time. However, in the process of mining copper and iron, certain autotrophic bacteria that grow spontaneously are used unknowingly to leach the minerals. There is a description in "Huainan Wanbi Shu" of the Western Han Dynasty that "Baiqing (copper sulfate) will turn iron into copper". This technology was widely used in the 11th century AD. In the late Northern Dynasty, "bile water leaching copper" was also recorded. The copper production accounted for 15% to 25% of the total output at that time. The Jiangxi Qianshan copper mining field alone had an annual output of 19× 104kg, Anhui Tongguanshan stope also exceeds Qianshan.
In recent years, the research and industrial application of microbial leaching in my country have made considerable progress. In terms of research on mineral leaching microorganisms, Zhang Dongchen, Zhang Mingxu and others questioned the view that plasmids are ubiquitous in Thiobacilli. Their research results showed that the ability of Thiobacillus ferrooxidans to oxidize Fe2+, S, etc. may only be related to nucleoid chromosomal DNA. Related, and the genetic material of Thiobacillus ferrooxidans is nucleoid chromosomal DNA. Xu Xiaojun, Meng Yunsheng, et al. reported that the leaching rate of chalcopyrite by UV-mutated mineral leaching bacteria increased by more than 46% compared with the original bacteria, and the time to reach the leaching end point was shortened by 5 to 10 days compared with the original bacteria. The mineral leaching bacteria can be more Good oxidative leaching of chalcopyrite. Zhao Qing, Liu Xiangmei and others used DNA in vitro recombination technology to construct a constitutively expressed arsenic-resistant plasmid pSDRA4 that contains a strong promoter and can be transferred under the induction of tra gene. The metallurgical engineering bacterium Acidithiobacilluscal dus (pSDRA4) was constructed by introducing it into the obligate autotrophic extreme acidophilic thermophilic Thiobacillus AcidithiobacilluscⅡIdW through conjugation transfer. After testing, the recombinant plasmid has good stability in the thermophilic Thiobacillus. , basically remained stable after 50 passages without selective pressure (more than 76% of the recombinant plasmid was retained). The arsenic resistance performance test showed that compared with wild bacteria, the arsenic resistance of the constructed Thiobacillus thermophila engineered bacteria was significantly improved, from 0 mmol /L increased to 45mmol/L. In terms of industrial application, bioleaching technology has been successfully applied to the Dexing Copper Mine in Jiangxi, and a heap leaching plant with an annual output of 2,000 tons of electric copper has been built. my country's first biological copper leaching pilot base was established in Dabaoshan, Guangdong. A thousand-ton biological copper extraction heap leaching plant has been built in Zijinshan, Fujian. The "Biometallurgical Technology Engineering" project of the National Tenth Five-Year Plan, undertaken by the Beijing General Research Institute of Nonferrous Metals and Fujian Zijinshan Mining Co., Ltd., will build a 10,000-ton biological copper extraction heap leaching plant in Zijinshan, Fujian. At the same time, biological pre-oxidation of gold concentrate has begun industrial application in Laizhou, Shandong. The biometallurgy of sulfide ores such as nickel and zinc has also been developed to varying degrees.
Generally speaking, the industrial application scale of biometallurgy in my country is small, there are few application mines, and the mineral types are single, so more efforts are needed to develop it. Since 90% of domestic primary sulfide ores are complex and low-grade, the application prospects of this technology are very broad. At present, Professor Qiu Guanzhou of Central South University as the chief scientist has officially launched the "Basic Research on Microbial Metallurgy". The project is supported by the Ministry of Education, with Central South University as the first undertaking unit, Beijing General Institute of Nonferrous Metal Research, Shandong University, and the Chinese Academy of Sciences. The Institute of Process Engineering, Beijing General Research Institute of Mining and Metallurgy, Changchun Environmental Research Institute and other units collaborate to undertake this project. This marks that basic research in the field of non-ferrous metal mineral processing and metallurgy in my country has entered a development stage that is in sync with the world's first-class levels.
Development trends and research directions of biometallurgy
Biometallurgy is a new process that combines bioengineering technology and traditional mineral processing technology through the interdisciplinary development of modern disciplines. The application of bioengineering to mineral processing is undoubtedly of great significance. The current development trends, research directions and problems that need to be solved mainly include: ① Selection of microorganisms affected by extreme conditions; ② Construction of genetically engineered bacteria; ③ Bioleaching mechanism; ④ Low concentration solution New technologies for the extraction of nickel, cobalt and other metals; ⑤ Optimization and control of the leaching process; ⑥ Research on heterotrophic bacteria leaching; ⑦ Development of efficient reactors; ⑧ Development of underground bio-leaching technology; ⑨ Precious metals and rare metals Biological adsorption research; ⑩ research on biological removal of sulfur in coal; research on desilication of bauxite; research on deironization of non-metallic minerals (such as kaolin); research on biological beneficiation agents.