With the continuous development of bauxite resources in China, high-quality dwindling resources. In order to solve the contradiction between the quality of bauxite and the quality requirements of alumina production for bauxite, the research on desiliconization of bauxite physical ore dressing is more common. And in the alumina production, the process of the beneficiation-Bayer process is applied. However, since the introduction of biological treatment technology into mineral processing, in recent years, in the beneficiation research of bauxite, the biological method to remove silica from bauxite has become a new research direction. The biological beneficiation desiliconization method is a promising beneficiation desiliconization method, which can ensure high process indexes and eliminate environmental pollution. Bio-mineralization desiliconization is the decomposition of silicate and aluminosilicate minerals by isoxic microorganisms. For example, bacteria can destroy a kaolin molecule into alumina and silica, thereby converting silica into soluble matter and oxidizing. Aluminum is insoluble and can be separated. This method is suitable for the treatment of colloidal ultrafine bauxite.
1. Samples, methods and experimental conditions
The test sample is a water area diaspore bauxite with Henan white mica. Grinding to make the fineness required for the beneficiation test.
(1) Bauxite sample material composition
The composition of the bauxite sample was identified by X-ray analysis. Which mineral components: 50% to 55% diaspore, 15% water, muscovite, kaolinite, 5% to 10% feldspar 5% to 7%, 5% anatase, 5% pyrophyllite, brown iron ore 3% to 5%.
The chemical analysis results of the sample: A1 2 O 3 63.68%, SiO 2 12.31%, FeO 0.06%, Fe 2 O 3 2.75%, TiO 2 3.91%, Na 2 O 0.05%, K 2 O 2.15%, MgO 0.23%, CaO 0.15%, SO 3 0.82% P 2 O 5 0.10 %, S 0.30%, C 0.36%, loss on ignition 13.2%, A1 2 O 3 /SiO 2 5.17.
Bauxite is dominated by granule structure. The main mineral component is diaspore, which has two main forms: a massive microcrystal and a longitudinally aligned crystal. Water mica is mostly colorless scales. Chlorite is a sparse scale in the water muscovite. The Ruiqin mine is a micro-long particle, and the limonite is an irregular massive aggregate of minerals, which exists in the center of the grain. Quartz exists in the acute angle fragments inside the granules.
Colloids are amorphous, isotropic (homogeneous), or heterogeneous (anisotropic), cemented with diaspore, hydromica and other minerals.
(2) Microbiological test methods
In combination with previous studies, the microorganisms used for desiliconization of bauxite during the test were bacterial species extracted from high silica bauxite. The cells were cultured in A-27 medium, and the solid-liquid ratio (S:L) was 1:5, and the strain was incubated in a thermostat at a temperature of 32 ° C for 7 days and nights. The strains were then observed and separated under a microscope.
The medium components are glucose, Na 2 HPO 4 , alumina, MgSO 4 , FeCl 3 , cullet, CaCO 3 , agar, and the like. The pH of the nutrient base is 6.8 to 7.2.
The desiliconization of bauxite is carried out using a culture of 4 days and nights of silicate. Biological experiments were carried out in shake flasks in both static and dynamic ways for 1 to 7 days and nights. In the meantime, shake the pH every day and night and take a picture under the microscope. Finally, the liquid phase is separated, the ore is washed with boiling water, dried, and ground for chemical analysis. The contents of Al 2 O 3 and SiO 2 were determined by atomic absorption.
Second, sample conventional ore dressing comparison experiment
In order to compare the biological experiment results, the flotation experiment was first carried out by a conventional flotation process. The equipment used was a 1 L flotation machine with a solid-liquid ratio of 1:4. The test was carried out according to the procedure of Figure 1. The results are shown in Table 1.
Figure 1 Flotation process
Table 1 Flotation experiment results
test Serial number | Pharmacy consumption kg/t | Flotation product | Yield % | A 2 O 3 % | SiO 2 % | Aluminum to silicon ratio | |||
grade | Recovery rate | grade | Recovery rate | ||||||
1 | Grinding: sodium carbonate = 3.0, coarse selection of water glass = 0.5, tall oil = 1.0, sweeping tall oil = 0.3, selected sodium carbonate = 3.0, water glass = 0.2, ON-7 = 0.3 tall oil = 0.3 | Concentrate | 60.5 | 68.87 | 67.1 | 5.87 | 26.3 | 11.85 | |
Middle mine | 11.8 | 55.22 | 10.5 | 20.38 | 17.8 | 2.71 | |||
Sweep Concentrate | 6.7 | 58.28 | 6.3 | 17.31 | 8.6 | 3.36 | |||
Tailings | 21.0 | 47.68 | 16.1 | 30.46 | 47.3 | 1.57 | |||
100.0 | 62.09 | 100.0 | 13.51 | 100.0 | 5.89 | ||||
2 | Grinding: sodium carbonate = 3.0, crude water glass = 0.5, oleic acid = 1.0, selected sodium carbonate = 2.0, water glass = 0.2, ON-7 = 0.3, oleic acid = 0.3, sweeping oleic acid = 0.5 | Concentrate | 10.0 | 63.70 | 10.0 | 10.82 | 8.5 | 6.81 | |
Middle mine | 30.1 | 66.38 | 31.7 | 9.75 | 22.7 | 5.11 | |||
Sweep Concentrate | 13.7 | 63.58 | 13.8 | 12.45 | 13.2 | 3.88 | |||
Tailings | 46.2 | 60.60 | 44.4 | 15.63 | 55.7 | ||||
100.0 | 63.05 | 100.0 | 12.95 | 100.0 | |||||
From the obtained beneficiation data, it is known that oleic acid is not effective as a collector during the flotation process. It is better to use tall oil in bauxite flotation. The recovery of the concentrate has an Al 2 O 3 recovery of 67.1% and an aluminum to silicon ratio of 11.85.
III. Results and discussion of bauxite biological beneficiation experiment
Biological dressings are generally used for unique microorganisms such as silicate. Silicon bacilli occupy an important position in the microbial world, they can destroy the crystal lattice of aluminum and silicon, as the energy of vitality. This special ability of this microorganism is used as a silica to destroy bauxite. However, the microbial leaching effect of silicon in silicate minerals is closely related to the way the microorganisms are leached.
The selected bauxite is a high silica bauxite mine. From the above experimental results, the flotation effect by the conventional beneficiation method is very good. However, its disadvantage is that the flotation agent is expensive, the Al 2 O 3 recovery rate is low, and a large amount of tailings is produced, which is not environmentally friendly.
(1) Experiment of SiO 2 dissolution in bauxite by static bacteria
Experiments were carried out under static conditions using different strains such as 1 # , 2 # , 3 # , and the results are shown in Fig. 2, Fig. 3, and Fig. 4.
FIG 21 under static strain # bauxite processing results
FIG 32 under static strain # bauxite processing results
FIG 43 under static strain # bauxite processing results
Under static conditions, the samples were subjected to silicon dissolving experiments using different strains, and 3 # bacteria showed good activity. 3 # bacteria were selected from the sample bauxite area. After 7 days and nights of the experiment, 43% of the silica was removed, and the alumina content in the ore was increased from 63.7% to 66.73%, and the aluminum to silicon ratio was 7.09. The experimental results show that as the biological experiment time prolongs, the bacteria begin to accelerate the extraction of silica in the solution.
(2) Experiment of SiO 2 dissolution in bauxite by dynamic bacteria
For the next step, more effective strains of silicate strains (2 # and 3 # ) were selected. Found in the bio-dissolved silicon experiment of the sample. With the continuous addition of new minerals, there is a flow cycle, as shown in Figures 5 and 6. The leaching speed of silica is 2 to 3 times faster, and the second day and night is more obvious. The recovery of SiO 2 in the solution was 35.9% with 2 # bacteria, 45.5% with 3 # bacteria, and 6.91 and 7.51 for aluminum to silicon ratio. The third day and night recovery rate has decreased. The alumina in the concentrate rose to 66.16% and 66.71%, and the concentrate recovery rate increased from 81.18% to 87.97%. It is noted that silica has a better leaching effect under dynamic conditions, not only is it fast, but also has a high recovery rate. It is more economical to process more minerals in less time. In addition to this, it is also possible to reduce the consumption in terms of the medium.
FIG strain # 52 under dynamic processing bauxite experimental results
FIG dynamic strain # 63 at the processing results bauxite
(III) Experiment on the dissolution of silicon from bauxite by bacteria under different pulp concentrations
Slurry density is very important in the production process because it is necessary to find the optimal growth conditions for the growth of microorganisms. And it must be considered from an economic perspective. Under laboratory conditions, silica leaching was carried out with 2 # bacteria, and the solid-liquid ratio was 1:10 and 1:5 with the same pulp density. This process is a dynamic process, and the experimental results are shown in Figure 7 and Figure 8.
Figure 7 2 #液液固 ratio 1:10 dissolution test results
Figure 8 2 #液液固 ratio 1:5 dissolution test results
The recovery rate was the best when the solid-liquid ratio was 1:5, and the optimum leaching time was 2 days and nights. The Al 2 O 3 in the concentrate was increased to 67.61%, the SiO 2 content was reduced to 9.51%, and the aluminum to silicon ratio was 7.11. The leaching process is more economical with a slurry to solid to liquid ratio of 1:3.
(IV) 2 # bacteria under the conditions of dissolved silicon experiment
Test conditions: In a device with a stirring device, 100 g of a sample and 500 ml of a concentrated silicate solution were added. It was carried out for 7 days and nights at 18 to 22 ° C without disinfection. The experimental results are shown in Figure 9.
Melting the silicon under the experimental results in FIG 92 # bacteria conventional conditions
The experimental results show that under these conditions, that is, to some extent close to the production conditions, the alumina is successfully increased to 67.66%. The silica is reduced to 8.97% and the aluminum to silicon ratio is 7.54.
(5) Combined biological method for the dissolution of silicon in bauxite
The beneficiation of bauxite by biological beneficiation technology can be used in combination with various beneficiation methods. Under the above conditions, various bauxite ore dressing methods are used. This includes experiments with continuous use of biopharmaceuticals and silicate bacteria (2 # ) for 1% mineral content. In this case, the aluminum to silicon ratio was 8.0 (Table 2). It should be noted that through the use of 3 # bacteria, better beneficiation results can be obtained. If the experimental process is intensified, the effect will be better if the slurry is transferred from the aligned vessels in sequence under dynamic conditions.
Table 2 Results of silicon-dissolved experiments on bauxite by combined biological methods
Serial number | product | Yield/% | content% | Recovery rate% | A/S | experiment condition | ||
Al 2 O 3 | SiO 2 | Al 2 O 3 | SiO 2 | |||||
1 | Concentrate | 95.80 | 64.09 | 11.45 | 96.38 | 86.84 | 5.60 | Biological reagent |
Tailings | 100.00 | 63.70 | 12.63 | 100.00 | 100.00 | 2 nights and nights | ||
2 | Concentrate | 90.60 | 65.67 | 8.20 | 93.40 | 58.82 | 8.00 | |
Tailings | 100.00 | 63.70 | 12.63 | 100.00 | 100.00 | Biological reagent plus 2 #èŒ2昼夜 | ||
Fourth, the conclusion
(I) The experimental results show that the bio-mineralization technology has obvious desiliconization effect on the selected sample bauxite.
(2) The preferred silicate bacteria can make the aluminum-silicon ratio of the bauxite concentrate reach 7.09 to 7.95, and the recovery rate of the concentrate alumina is 80% to 86%.
(3) Using a mixture of biological agents and silicate bacteria, the ratio of refined aluminum to silicon is 8.0, and the recovery rate of refined alumina is 93.4%.
(4) Biological beneficiation has broad prospects for the beneficiation of sample bauxite. High quality concentrates are available to meet the industrial production needs of Bayer process for the production of alumina.
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