Biological metallurgy technology industrialization began in the 20th century copper mine in the 1960s, uranium, to the 1980s, biological metallurgy technology development more quickly, and to study the large-scale industrial applications, in terms of biological organisms metallurgical metallurgy of copper, uranium, gold, etc. The application field has been expanded from the extraction of copper, uranium and gold to the fields of nickel , cobalt , zinc , molybdenum , phosphorus and coal desulfurization. By 1999, the biological extraction of nickel-cobalt ore has also been realized industrially, marking nickel-cobalt. The biometallurgy of the mine has moved from the laboratory to industrial applications. Practice has proved that the cost of producing nickel-cobalt by biological method is much lower than the production cost of traditional technology.
Since the 1980s, some domestic research institutes such as the Beijing Research Institute of Nonferrous Metals, the Institute of Process Engineering of the Chinese Academy of Sciences, and the Central South University have begun research on the mechanism of bacterial leaching of nickel sulfide ore. after believes that bacterial leaching of nickel by pyrite complex mechanism of control. The Beijing Research Institute of Nonferrous Metals has selected excellent nickel leaching strains from Jinchuan Nickel Mine. The leaching rates of lean ore and tailings nickel are 88% and 87% respectively. The high pH immersion is selected by laser mutagenesis. Nitrogen-producing bacteria has initially solved the problem of pH instability caused by the acid-consuming gangue of Jinchuan nickel ore, which affects the bacterial activity. It shows that biometallurgical technology has a good application prospect in the development and utilization of nickel ore resources in China.
In this study, high- arsenic- sulfur, low-nickel-cobalt sulfide ore was selected as the research object. The main mineral containing nickel is arsenic-nickel ore. While leaching nickel, arsenic is also leached at the same time. The high arsenic content has a great influence on the normal growth and reproduction of bacteria. Compared with the leaching of nickel-bearing pyrite or nickel-bearing pyrrhotite reported in the literature, the selection and improvement of anti-arsenic bacteria are needed to improve the efficiency of bacterial leaching. In this study, the bioleaching process mineralogy was studied in detail by using modern process mineralogy research methods such as chemical analysis and mineralization of polarized mineral phase microscopy, modern microbial domestication breeding technology and leaching activity detection technology, and ore shake flask bacterial leaching method. The key process parameters of high-efficiency leaching strains and bacterial leaching of high-resistance leaching strains have obtained high-efficiency leaching strains and bioleaching optimal process parameters for high-arsenic-sulfur, low-nickel-cobalt sulfide ore leaching, in order to further develop low-grade grades. The biological extraction of nickel sulphide ore deposits provides a technical basis.
I. Research methods, materials and leaching strains
(1) Research methods
Ore process mineralogy research method: select representative ore specimens, make light sheets through cutting, rough grinding, fine grinding and polishing, and then identify mineral species and mineral quantity statistics under a mineral microscope. The chemical composition of the mineral is quantitatively determined by ICP2MS chemical analysis in the ore sample.
Selection and domestication of leaching bacteria: According to the physicochemical properties and ore composition of the ore, select the appropriate original leaching strain, add a certain concentration of Ni 2+ , Co 2+ metal ions and arsenic in 9K medium, and then gradually The concentration of Ni 2+ , Co 2+ metal ions and arsenic is increased, and each time is transferred to a high arsenic-sulfur low-nickel-cobalt sulfide ore leaching system to improve leaching performance and anti-toxic domestication. At the same time, the leaching activity of domesticated bacteria was determined by ferrous ion oxidation rate method, biological microscope direct counting method and redox potential method.
Ore bacteria shake flask leaching test method: weigh a certain amount of mineral powder, add it to a 300ml triangle bottle, put it into a pressure cooker for steam sterilization for 20min, cool it and then add the disinfected bacterial basal medium to adjust the acidity to the desired The pH is made constant, then the bacteria are connected and placed in an air-controlled shaker to oscillate. During the leaching process, the pH value and potential of the slurry were measured once a day, and the pH of the slurry was adjusted with 20% diluted H 2 SO 4 or 10% NaOH solution. After the leaching is completed, the leaching slag is filtered, washed, dried, and the leaching slag and the leachate are separately analyzed.
(2) Experimental and testing instruments
Polarized mineral phase microscope: identification of minerals; temperature-controlled stepless speed regulation shaker: cultivation of strains; autoclave: sterilization of vessels and culture medium; Thermo orion model 868 potential pH meter: detection of bacterial culture and leaching process pH value; potentiometer: detection of bacterial liquid and slurry potential (vs. SCE), the electrode used is standard calomel electrode and platinum electrode; biological microscope (including CCD digital camera and transmission) system: detection of bacterial activity in solution Atomic absorption spectrometer: analysis of the content of metal elements in leachate and leaching residue; spectrophotometer: detection of bacterial concentration and analysis of leachate and leaching metal
(3) Materials
Chemicals used (AR) are: ferrous sulfate, ammonium sulfate, magnesium sulfate, calcium nitrate, dipotassium hydrogen phosphate, potassium chloride, potassium fluoride, sulfuric acid, sodium hydroxide, hydrochloric acid, phosphoric acid and ammonia.
(4) Leaching strains
The original leaching strain for the test was Retech I, Retech III, Retech V.
Second, the results of process mineralogical research
The chemical composition of the ore is shown in Table 1. The main beneficial components in the ore are nickel and cobalt, and other useful components.
Table 1 Chemical composition of ore
The content of Mn, Pb, Cu and Zn is low, and the harmful component is arsenic. The components of the metal minerals constituting the ore are mainly iron and sulfur, and the components constituting the gangue mineral are mainly silica and alumina , and the calcium oxide and magnesium oxide are lower.
The relative contents of the various minerals constituting the ore are shown in Table 2. The metal minerals in the ore are mainly pyrite, followed by pyrite, pyrite and limonite, hematite; nickel-bearing minerals are pyrite nickel, tourmaline, nickel ore, orthorhombic nickel ore. , Nickel and so on. The gangue minerals are mainly quartz and hydromica , and a small amount of chlorite; there are few carbonate minerals, and a small amount of siderite and magnesite .
Table 2 Mineral composition and relative content of ore
Pyrite is the main carrier mineral of beneficial components of nickel and cobalt; pyrite has a poor degree of crystallinity, loose structure, easy to be etched by bacteria, and nickel and cobalt are also easily leached.
There is a part of fine nickel-containing minerals in the ore, and it is dispersed in the dense gangue. It is not easy to dissociate or expose the monomer. It is difficult to contact with the high-iron liquid in the bioleaching, which will affect the nickel leaching rate. main reason.
The results of the material composition of the above ore indicate that the ore consumption of the ore is small during the bioleaching process; since the metal sulfide ore in the ore is high in sulfur and iron, and the sulfur and iron in the pyrite are mainly, the bacteria leaching nickel In the case of cobalt, pyrite is also oxidized to produce more acid and more iron is leached, which adversely affects the extraction of nickel and cobalt in the bioleaching solution.
3. Selection, domestication and activity determination of leaching microorganisms
(1) Selection of leaching microorganisms
According to the physicochemical properties and ore composition of the ore, select the appropriate test strains from the biochemical metallurgical national engineering laboratory leaching strain bank, numbered Retech I, Retech III, Retech V, and use high-arsenic in iron-free 9K medium. The selective domestication of sulfur-low nickel-cobalt sulfide ore is shown in Table 3.
Table 3 Selection test results of leaching strains
It can be seen from Table 3 that the strain of Retech III is more suitable for leaching of the high arsenic-sulfur, low-nickel-cobalt sulfide ore, and the nickel-cobalt leaching effect is better. Therefore, the domestication of the strain is carried out with the Retech III strain.
(2) Domestication of leaching microorganisms
The domestication of the strain Retech III was mainly to improve its adaptability to the properties of the ore and its tolerance to metal ions Ni 2+ , Co 2+ and arsenic. Acclimatization process is directly added in a concentration of 9K medium Ni 2+, Co 2+ metal ions and arsenic, and then gradually increase the Ni 2+, Co 2+ metal ions and arsenic concentrations, and each adapter in the ore leaching system Domesticated. The first generation domestication conditions: Ni 2+ 1g·L -1 , Co 2+ 0.5g·L -1 , As0.5g·L -1 ; Second generation domestication conditions: Ni 2+ 2.5g·L -1 ,Co 2+ 1.5g·L -1 , As1.0g·L -1 ; third generation domestication conditions: Ni 2+ 5.0g·L -1 , Co 2+ 3.0g·L -1 , As2.5g·L -1 . The test results are shown in Table 4.
Table 4 RetechIII adaptive domestication leaching test results
The test results show that the anti-toxicity and the ability of immersion nickel and cobalt are improved after the actual ore and metal ions Ni 2+ , Co 2+ and arsenic acclimated strains, indicating that the adaptability and leaching activity of the strain are actually after acclimation. The stability in the ore is enhanced.
(III) Determination of activity of leaching microorganisms
The activity of leaching microorganisms is an important parameter for bacterial leaching. In order to investigate the leaching activity of Retech III three-generation domesticated bacteria, the leaching activity of Retech III three-generation domesticated bacteria was determined by ferrous ion oxidation rate method, biological microscope direct counting method and redox potential method. The measurement conditions were: 9K medium. , Ni 2+ 5.0g·L -1 , Co 2+ 3.0g·L -1 , As2.5g·L -1 , initial bacterial concentration 3.78×10 5 cells·ml -1 , shaker temperature 30 ° C, rotation speed 145 r · min -1 , the results are shown in Figures 1-3.
Fig.1 Curve of the oxidation rate of Fe 2+ to Fe 3+ by Retech III three-generation domesticated bacteria
Fig. 2 Curve of redox potential of bacterial liquid during bacterial culture
Figure 3 Curve of bacterial culture time and logarithm of live bacteria concentration in bacterial solution
The results of leaching activity of Retech III three-generation domesticated bacteria showed that the strain had higher activity, and the rate of Fe 2+ oxidation to Fe 3+ reached 1.4g·(L·h) -1 ; The concentration was 1.67×10 8 cells·ml -1 from the initial 3.78×10 5 cells·ml -1 for 60 hours, and the stable period was longer; the potential of the solution was close to 600 (mV, vs. SCE), and the oxidation ability was strong.
IV. Results and analysis of nickel and cobalt bioleaching test
(1) Having bacteria and aseptic comparison test
Test conditions: pulp concentration 5%, pulp pH value 2.0, leaching time 16d, leaching temperature 30.3 °C, shaker speed 145r·min -1 , other test conditions and results are shown in Table 5.
Table 5 Results of comparison between bacteria and no voyage
(II) Effect of initial pH value of leaching medium on bioleaching of nickel and cobalt
Test conditions: pulp concentration 5%, bacterial inoculum size 20%, leaching time 20d, leaching temperature 30.3 ° C, shaker speed 145r·min-1, other test conditions and results are shown in Table 6.
Table 6 Initial pH test results of leaching medium
The experimental results show that the initial pH value of the leaching medium has a significant effect on the leaching of nickel and cobalt in the high arsenic nickel-cobalt ore. The too high and too low initial pH values ​​are not conducive to the leaching of nickel and cobalt. Therefore, selecting a suitable pH value of the leaching medium (1.50 to 2.0) and stably controlling the pH value is very advantageous for increasing the leaching rate of nickel and cobalt. At the same time, the bacteria used in the leaching test were also shown, and the optimum growth pH was between 1.50 and 2.0.
(3) Relationship between bacterial inoculum and bioleaching of nickel and cobalt
The inoculum size and test results are shown in Table 7. Other test conditions are: pulp concentration 5%, initial pH of the leaching medium is 1.90, leaching time is 20d, leaching temperature is 30.3 °C, and shaker speed is 145r·min -1 .
Table 7 Results of bacterial inoculum test
The results showed that the leaching rate of nickel and cobalt was affected by the amount of bacteria inoculated. The leaching rates of nickel and cobalt were 23.29% and 26.25% respectively in the aseptic leaching. After the inoculation amount reached 30%, the leaching rates of nickel and cobalt reached 71.23. % and 97.52%, indicating that increasing the amount of bacterial inoculation is beneficial to accelerate the leaching rate of nickel and cobalt. The main reason is to increase the concentration of bacteria inoculation, shorten the adaptation period of bacteria in the new leaching environment, that is, shorten the stagnation period of bacteria and quickly enter the growth and reproduction period of bacteria.
(4) Effect of slurry concentration on bioleaching of nickel and cobalt
The slurry concentration and test results are shown in Table 8. The other test conditions are: bacterial inoculum is 20%, the initial pH of the leaching medium is 1190, the leaching temperature is 30.3 °C, and the shaking speed is 145 r·min -1 .
Table 8 Results of slurry concentration test
The test results show that the slurry concentration has little effect on the bacterial leaching of nickel-cobalt when the leaching time is long enough; only in the short-term bacterial leaching process, the pulp concentration has a great influence on the leaching rate of nickel and cobalt. Bacterial leaching for 10d, the concentration of pulp is less than 10%, the leaching rate of nickel is close to 60%, the leaching rate of cobalt is close to 80%, and the concentration of pulp is above 15%, the leaching rate of nickel and cobalt is drastically reduced, nickel and cobalt The leaching rate decreased to 45% and 60% respectively; the bacteria leached for 20 days, the pulp concentration was 5% to 30%, and the leaching rates of nickel and cobalt reached 70% and 97%, respectively.
(V) Effect of leaching cycle on bioleaching of nickel and cobalt
The leaching period and test results are shown in Table 9. Other test conditions are: pulp concentration 10%, bacterial inoculum 20%, leaching medium initial pH 1.90, leaching temperature 30.3 ° C, and shaker speed 145 r·min -1 .
Table 9 Leaching cycle test results
The test results show that the leaching period has a great influence on the leaching rate of nickel and cobalt. With the extension of the leaching period, the leaching rate of nickel and cobalt increased. However, when the leaching period was extended to 20 days, the leaching period was extended, the leaching rate of nickel and cobalt was gradually reduced, and the leaching period was extended to 100 days. The leaching rate of nickel and cobalt was extended. At 85.46% and 99.23%, respectively, the cobalt in the ore is almost completely leached.
(6) Bioleaching process parameters optimization test results
The optimization test of bioleaching process parameters of high-arsenic and low-grade nickel-cobalt-sulphide ore is based on the mineralogical study results of ore bioleaching process and the bioleaching characteristics of nickel-cobalt sulfide ore. The main influencing factors of bio-immersion nickel-cobalt are investigated. Through the experimental research on the main influencing factors such as leaching medium, leaching microorganism, leaching period, slurry concentration and temperature, the optimal process parameters are as follows: the leaching strain is Retech III three-generation domesticated leaching strain, the pulp concentration is 10%, The bacterial inoculum was 20%, the leaching pulp pH was 1.5-2.0, the leaching pulp temperature was 30 °C, the leaching time was 20d, and the shaker speed was 145r·min -1 . According to the above optimal process parameters, the leaching rates of nickel and cobalt reached 72.33% and 98.58%, respectively.
V. Conclusion
(1) A high-arsenic-sulfur low-nickel-cobalt sulfide ore contains a part of the nickel-containing minerals finely dispersed in the dense gangue, which is the main reason affecting the leaching rate of nickel bacteria; due to the acid-soluble gangue in the ore Low amount and high content of sulfur and iron in pyrite, so the ore consumes less acid during the bioleaching process, while the bacteria oxidize pyrite to produce more acid and leaching more iron, which is for bioleaching The extraction of nickel and cobalt has an adverse effect.
(2) The selected Retech III strain is more suitable for leaching of a high arsenic-sulfur, low-nickel-cobalt sulfide ore after acclimation, and the nickel-cobalt leaching effect is better. The bacteria can tolerate higher concentrations of heavy metal ions such as nickel, cobalt and arsenic. The toxicity is high, the leaching activity is high, and the ability of bacteria to oxidize Fe 2+ to Fe 3+ reaches 1.4g·L -1 ·h -1 ; the bacterial growth rate is fast, the bacteria culture is 60h, and the bacterial concentration is 3.78×10 5 at the initial time. The cells·ml -1 rose to 1.67×10 8 cells·ml -1 , and the stabilization period was longer; the potential of the solution was close to 600 (mV, vs. SCE), and the oxidation ability was strong.
(3) After optimizing the process conditions of bioleaching of nickel and cobalt, the leaching rate of nickel and cobalt bacteria in a high arsenic-sulfur, low-nickel-cobalt sulfide ore was improved, and three generations of high-efficiency leaching strain Retech III suitable for the ore properties were obtained. The technological parameters of bacteria and bacteria leaching, the leaching rates of nickel and cobalt reached 85.46% and 99.23%, respectively.
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