I. Introduction Biological metallurgy is a direction to establish environment-friendly mode of metallurgy, but compared with conventional wet leaching process, the existing bacterial oxidation of sulfide ore leaching technology in processing of sulfide ore still do not really have a competitive advantage, mainly due to slow leaching The leaching period is long, which makes the operating cost high, and the application is limited to some high-value low-grade sulfide ore. The research and development of temperature-resistant bacteria leaching technology is a key step to improve the reaction speed. Biological metallurgical technology currently used in most ferrous ferrooxidans (Thiobacillus ferrooxidans) leaching non-ferrous metals, non-ferrous metals while biologically important molybdenum, nickel leaching reported less, and is limited to bacteria at room temperature. Some researchers use normal temperature bacteria to leach low-grade molybdenum ore, but the leaching rate is not ideal and the leaching period is long. One of the reasons is that the normal temperature bacteria have poor anti-molybdenum ability. Yang Xianwan et al treated a low-grade ore containing Cu and Mo with Thiobacillus ferrooxidans and leached for 60 d at 30 °C. The Cu leaching rate was 60%, while the Mo leaching rate was only 0.34%. Donati et al. found that Thiobacillus ferrooxidans was not adsorbed on the surface of MoS 3 because Mo was toxic to bacteria. Studies by Hammaini et al. [8] showed that T. ferrooxidans leaching in 9K medium, 1 mmol/L molybdenum inhibited iron oxidation, and 2 mmol/L completely inhibited iron oxidation. The domestication can greatly improve the resistance of bacteria to molybdenum. Tong Xiong and other studies have shown that the leaching rate of molybdenum ore leaching is 5 times faster than that of sterile. Only 15 to 25 mg/L of molybdenum leaching solution can be obtained before the bacteria adapt to the mineral, and can be increased to more than 200 mg/L by domestication. In this work, Sulfolobus metallicus thermophilic bacteria were used as domesticated leaching strains, and the leaching of nickel-molybdenum ore was systematically studied and compared with the leaching ability of normal temperature bacteria. The results showed that the leaching of nickel-molybdenum ore by the thermophilic bacteria of the archaea could overcome the defects of long leaching period and low leaching rate of the normal temperature bacteria, especially in the stability of molybdenum resistance. The research results are expected to provide an important basis for the process design and application of biological methods for extracting precious metals such as nickel and molybdenum, and are of great significance for the breeding and expansion of rare metal bioleaching strains. Second, the experiment (1) Materials, reagents and instruments The ore sample used is Guizhou nickel-molybdenum sulfide ore. Its nickel-containing minerals are mainly disulfide nickel ore (NiS 2 ), nickel ore (Ni 3 S 4 ) and arsenic nickel ore (NiAsS), and small or micro-needle nickel ore ( NiS) and purple sulphur nickel ore (FeMnS 4 ), sulphur ilmenite and nickel-bearing pyrite, etc., the ore contains an average of 5% of molybdenum, of which the molybdenum mineral is a colloidal aggregate (gel sulphur sulphide ore) , Jordisite), therefore, X-ray diffraction analysis did not detect the presence of molybdenum sulfide. Intensive mineralogical studies have shown that this molybdenum aggregate is the main element in addition to sulfur and molybdenum, so it is called “carbon sulfur molybdenum oreâ€. Since the atomic weight of carbon is low, semi-quantitative analysis of the spectrum is not detected. The main components of minerals are shown in Table 1 and Figure 1. Table 1 Semi-quantitative analysis results of Guizhou nickel-molybdenum sulfide ore Figure 1 Mineral X-ray diffraction pattern Before the experiment, the ore sample was dried and finely ground to the required particle size. Strain: Sulfolobus metallicus (purchased from the Japanese Culture Collection) is an archaea that can grow aerobicly and can both oxidize S and oxidize Fe 2+ . The optimum temperature is 65 ° C and cultured with M174. Base culture (see Table 2 for ingredients). Thiobacillus ferrooxidans was provided by the Institute of Microbiology, Chinese Academy of Sciences and cultured in 9K medium (see Table 3). Table 2 M174 medium of Thiosol Table 3 9K medium Reagents and Instruments: ammonium sulphate, borax, sodium molybdate, vanadyl sulfate, such as yeast; Hitachi F-2500 fluorescence spectrophotometer, XSP-24N-103 type biological microscope, TZL-16 high-speed centrifuge, THZ-82 Constant temperature water bath oscillator, PHS-29A digital pH meter, atomic absorption meter. (2) Experimental methods 1. Domestication of bacteria and preparation of iron-free cell suspension Bacterial acclimation: Before the leaching experiment, Sulfolobus metallicus was domesticated under the same mineral and pulp concentration conditions to adapt the bacteria to the leaching environment and improve the molybdenum resistance of the strain. Acclimation conditions: 1 g of nickel-molybdenum ore with a particle size of <200 mesh (0.077 mm) was added to a 150 mL flask containing 100 mL of medium, and the inoculum was 10% (cell concentration was 1.8×107 mL−1), pH 1.6. In a shaker at a temperature of 65 ° C, the culture was shaken at a speed of 200 r / min, and domesticated for 3 times, about 5 days each time. Finally, the ore was centrifuged at 3000 r/min, and the domesticated bacteria were collected by centrifugation at 10000 r/min as a leaching strain. If it is immediately leached, it can be connected to the leaching solution, otherwise it will be stored in the refrigerator at 4 °C. The cell count was performed using a hemocytometry plate method. Preparation of iron-free cell suspension: The cultured bacterial solution was centrifuged at 3000 r/min for 10 min in a low-speed centrifuge to remove large particles of sediment in the bacterial solution, and the supernatant was separated by a high-speed centrifuge. After centrifugation at 10000 r/min for 30 min, the cell pellet was washed with sterile distilled water of pH 1.8, washed several times and diluted to the original volume, and the collected cells were immediately used or stored in a refrigerator at 4 °C. 2, shake flask leaching The immersion samples were repeated 3 times under different conditions, and the average value was taken. The medium was 100 mL, the inoculum was 10% (φ), the initial pH was 2 (this value was always maintained during the leaching process), the temperature was 65 ° C, the rotation speed was 200 r / min, and the leaching time was 20 d. Each flask was weighed before dip, sampled periodically, and replenished with evaporated water and removed medium. The leaching rate was calculated as the slag sample leached for 20 d. The slag leached for 20 days was suction filtered, and the leaching residue was washed several times with 1% diluted hydrochloric acid, dried, and weighed to determine the contents of Ni and Mo. Third, the results and analysis (1) Bacterial leaching results under sterile, domesticated and non-acclimated conditions In this study, bacterial leaching into sterile group to Fe 2+ as acclimation culture of bacterial leaching energy group to Fe 2+ leaching non-acclimated group of energy cultured to S 0 is the set of energy acclimation culture of bacterial leaching, in order to S 0 is a non-acclimated bacterial leaching group for energy culture, and is sequentially numbered No. 1 to 5. The slurry concentration is 10 g/L, the mineral particle size is <325 mesh (0.048 mm), and the leaching results are shown in Table 4. It shows that under the same conditions, the bacteria group (No. 2 to 5) is more sterile than the group (No. 2). 1) The nickel and molybdenum leaching rates are much higher. The nickel leaching rate in the bacteria group was above 90%, while the aseptic group was only 77.64%; the molybdenum leaching rate was also much higher. The leaching rate of the domesticated group was slightly higher than that of the non-domestic group. The leaching rate of domesticated bacteria (No. 4) cultured with S 0 was higher than that of non-acclimated bacteria (No. 5). The nickel leaching rates were 93.33% and 91.78%, respectively, and the molybdenum leaching rates were 68.66% and 65.98, respectively. %; the leaching rate of domesticated bacteria (No. 2) cultured with Fe 2+ was higher than that of non-acclimated bacteria (No. 3), the nickel leaching rates were 94.70% and 93.10%, respectively, and the molybdenum leaching rate was 70.20. % and 68.40%. It can be seen from Table 4 that No. 2 has a slightly higher leaching rate than No. 4, and the nickel leaching rates are 94.70% and 93.33%, respectively, and the molybdenum leaching rates are 70.20% and 68.66%, respectively. The acclimation group has a higher leaching rate than the non-domestic group because the acclimated bacteria can adapt to the leaching environment more quickly, and are more resistant to shear forces in the medium and increasing molybdenum toxicity. In addition, the nickel leaching rate is much higher than that of molybdenum, and is related to the chemical composition, crystal form, lattice structure, surface ionization energy, electrode potential, conductivity type, and ion species and content in the medium. From the crystal form and conductivity type, MoS 2 belongs to the hexagonal system, and the conductivity type is N type and P type. The P type conductor is released from the low electron energy level during oxidation, and is harder to oxidize than the N type conductor. From the thermodynamic point of view, the smaller the potential of the mineral is, the better the leaching is because the true electron acceptor in the leaching process is dissolved in the leaching solution. The smaller the mineral potential, the greater the potential difference from oxygen, and the thermodynamic trend of oxidation. The larger the NiS 2 is a metal conductor with a low potential (only 0.146 V) and easy to leach. Nickel-molybdenum sulfide ore is due to the presence of both disulfide ore (NiS 2 ), nickel ore (Ni 3 S 4 ), nickel ore (NiS) and MoS 2 , nickel sulfide ore and molybdenite (potential 0.5 V) The electrostatic potential is different, and the galvanic effect is formed. The former has a lower potential and the anode reaction preferentially dissolves, while the latter has a higher potential and is cathodically protected, and the dissolution is difficult. In addition, although molybdenite can be oxidized by Fe 3+ to form molybdic acid, the solubility of molybdic acid produced in water is small because the formation of molybdic acid in water requires a solution potential of more than 600 mV. Table 4 Leaching results under different culture conditions Aluminum Extrusion Parts Processing,Extrusion Parts Processing,Extrusion Parts,Cnc Aluminum Extrusion Parts Dongguan Kingswin Wing Tat Metal Products Co., Ltd. , https://www.milling-turning.com
Leaching of nickel-molybdenum sulfide ore by Sulfolobus