A biological passivation agent for passivating metal sulphide mine tailings and a method of passivation thereof

Abstract

The application discloses a kind of biological passivation agent for passivating metal sulfide ore tailings.The biological passivation agent for passivating metal sulfide ore tailings is culture containing marine calcifying microorganism.The application also discloses a passivation method of the biological passivation agent for passivating metal sulfide ore tailings, comprising the following steps: the biological passivation agent is added into seawater according to at least 1:100 ratio;The metal sulfide tailings are immersed in seawater containing the biological passivation agent, and soaked for not less than 20 days, so that a layer of organic-inorganic passivation layer with aragonite structure is formed on the surface of the metal sulfide ore tailings.The application provides a biological passivation agent for passivating metal sulfide ore tailings and its passivation method, which is simple to operate, low in cost, non-toxic to the environment, and can be combined with seabed tailings treatment technology to control the generation of AMD from the source and release the occupied land.

Description

Technical Field

[0001] This invention relates to the field of tailings management technology, specifically to a biological passivating agent and a passivation method for passivating metal sulfide tailings. Background Technology

[0002] Metal sulfides are among the most unstable and common minerals in the Earth's surface environment. In the presence of water, air, and microorganisms, sulfides are easily oxidized and decomposed, releasing metal ions and generating sulfuric acid, resulting in acid mine drainage (AMD). AMD water has an extremely low pH and is rich in heavy metal ions; its formation and migration severely damage the ecological environment and harm human health. However, mineral resources are the material foundation of a country's economic development, and their extraction is enormous. According to relevant research statistics, up to 10 billion tons of tailings are generated worldwide each year. These tailings contain metal sulfides and are directly dumped in open tailings ponds. Therefore, AMD has become another global environmental problem after the greenhouse effect. In my country, as of early 2020, there were approximately 8,000 tailings ponds with a tailings accumulation exceeding 70 billion tons, and streams polluted by AMD stretched for at least several thousand kilometers. Therefore, controlling and managing AMD formed during mining operations is urgently needed.

[0003] AMD's remediation technologies are divided into end-of-pipe remediation and source control technologies. Among source control technologies, surface passivation is one of the most effective and promising methods. Among the many effective tailings surface passivating agents currently available, organosilane passivating agents have been proven to effectively reduce the chemical or biological oxidation rate of tailings by forming a hydrophobic passivation film on the surface of metal sulfides. However, these passivating agents are formulated from various organic and inorganic reagents, resulting in high costs and a relatively complex coating process. They also suffer from insufficient long-term effectiveness and secondary pollution, hindering their widespread adoption. Therefore, it is essential to develop economical, long-lasting, simple, and environmentally friendly technologies. Summary of the Invention

[0004] To address the technical problems of existing organosilane passivating agents, such as high cost, complex coating process, insufficient long-term effectiveness, and secondary environmental pollution, this invention provides a biological passivating agent and its passivation method for passivating metal sulfide tailings. The biological passivating agent is prepared from marine calcifying microorganisms. Utilizing the ability of these microorganisms to induce the production of calcium carbonate minerals, the agent grows on the surface of metal sulfides in a seawater environment, forming an organic-inorganic composite layer with an aragonite structure. This layer blocks air, water, and iron-sulfur oxidizing microorganisms, thereby achieving the passivation of the metal sulfides. This passivation method is simple to operate, low in cost, and non-toxic to the environment. Furthermore, it can be combined with Submarine Tailings Disposal (STD) technology to control the generation of AMD (metal sulfide tailings) at its source and release occupied land.

[0005] This invention provides a biological passivating agent for passivating metal sulfide tailings, wherein the biological passivating agent is a culture containing marine calcifying microorganisms.

[0006] In a preferred embodiment of the biological passivating agent for passivating metal sulfide tailings provided by the present invention, the marine calcifying microorganisms include at least one of *Rhizobium flavum* and *Pseudomonas lipolyticis*.

[0007] In a preferred embodiment of the bio-passivating agent for passivating metal sulfide tailings provided by the present invention, the concentration of viable bacteria of the marine calcifying microorganisms in the bio-passivating agent is not less than 10. 8 cells / mL.

[0008] In a preferred embodiment of the bio-passivating agent for passivating metal sulfide tailings provided by the present invention, the concentration of the marine calcifying microorganisms in the bio-passivating agent is 10. 9 ~10 10 cells / mL.

[0009] The present invention also provides a passivation method based on the aforementioned bio-passivating agent for passivating metal sulfide tailings, comprising the following steps:

[0010] The biological passivating agent is added to seawater at a ratio of at least 1:100;

[0011] The metal sulfide tailings are immersed in seawater containing the biological passivating agent for no less than 20 days to form an organic-inorganic passivation layer with an aragonite structure on the surface of the metal sulfide tailings.

[0012] In a preferred embodiment of the passivation method based on the bio-passivating agent for passivating metal sulfide tailings provided by the present invention, the organic-inorganic passivation layer with aragonite structure is a composite passivation film of calcium carbonate with aragonite structure and bacteria.

[0013] In a preferred embodiment of the passivation method based on the bio-passivating agent for passivating metal sulfide tailings provided by the present invention, the pH value of the seawater system is 7.0 to 8.5.

[0014] In a preferred embodiment of the passivation method based on the bio-passivating agent for passivating metal sulfide tailings provided by the present invention, the bio-passivating agent is used at a temperature between 15 and 37°C.

[0015] In a preferred embodiment of the passivation method based on the bio-passivating agent for passivating metal sulfide tailings provided by the present invention, the bio-passivating agent is used at a temperature of 25-37°C.

[0016] In a preferred embodiment of the passivation method based on the bio-passivating agent for passivating metal sulfide tailings provided by the present invention, the metal sulfide tailings include at least one of pyrite, chalcopyrite, and sphalerite waste rock.

[0017] Compared with existing technologies, the bio-passivating agent for passivating metal sulfide tailings provided by this invention has the following beneficial effects:

[0018] I. This invention provides a biological passivating agent, the active ingredient of which is marine calcifying microorganisms, such as *Gibberella flavonoids* and / or *Pseudomonas lipolyticis*. These microorganisms are widely distributed in marine environments, such as seabed mud or coral reefs, and therefore are harmless to the environment and human body. Compared with other surface passivation methods, this biological passivating agent is inexpensive, easy to use, environmentally friendly, and harmless to human body, making it an environmentally friendly passivating agent.

[0019] II. The bio-passivating agent provided by this invention can generate an organic-inorganic composite passivation film with an aragonite structure on the surface of metal sulfide tailings. This passivation film has a dense and stable structure, which can effectively block oxidizing substances from corroding sulfides. Moreover, this passivation film will continue to form in seawater and can be combined with Submarine Tailings Disposal (STD) technology to control the generation of AMD from the source and release occupied land. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0021] Figure 1 The images are scanning electron microscope images of pyrite powder flakes before and after biopassivation in Example 2.

[0022] Figure 2 This is a laser confocal scanning microscope image of pyrite powder after biopassivation in Example 2.

[0023] Figure 3 The changes in Fe content and pH of the leachate over time are shown in Example 2.

[0024] Figure 4 Macroscopic images of unpassivated and biopassivated pyrite powder flakes from Example 2 after leaching in 0.5% (v / v) H2O2 at different initial pH for 180 days.

[0025] Figure 5 In Example 2, Shanghai bok choy seedlings that had grown for 28 days were irrigated with leachate from unpassivated and biopassivated pyrite powder flakes after 180 days.

[0026] Figure 6 In Example 2, onion seedlings that had grown for 28 days were irrigated with leachate from unpassivated and biopassivated pyrite powder flakes after 180 days.

[0027] Figure 7 This is a scanning electron microscope image of pyrite particles after biopassivation in Example 3.

[0028] Figure 8 Fourier transform infrared spectrum of the bio-organic-inorganic coating on the surface of pyrite particles in Example 3. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The bacteria used in this example is *Erythrobacter flavus*, purchased from the China Culture Collection Center for Microbial Cultures, catalog number Bio-04483. The strain was preserved in 2216E liquid medium containing 20% ​​glycerol at a temperature of -80°C.

[0031] The chemical composition of the bio-organic-inorganic passivation layer in the examples was identified using Fourier transform infrared spectroscopy.

[0032] The seawater in the embodiment was collected from the South China Sea. After sedimentation and filtration, peptone and yeast powder were added for sterilization. The contents of peptone and yeast powder were controlled at 0.5% and 0.1%, respectively.

[0033] Example 1: Preparation of biological passivating agent

[0034] Take a strain of bacteria stored at -80℃ and inoculate one loopful into 150 mL of 2216E medium. Then, incubate at 30℃ and 100 rpm in a shaker. After 12 hours, the bacterial concentration can be counted using a hemocytometer. Adjust the bacterial culture to a concentration of 10⁻⁶. 8 After reaching cells / mL, it can be added to seawater at a ratio of 5mL of bacterial solution per liter of seawater.

[0035] Example 2: Determination of passivation properties of pyrite

[0036] Pyrite was crushed and ground, and then sieved through a standard sieve to obtain pyrite powder with a particle size ranging from 43 to 74 μm. A 6.6 x 1.8 cm (length x width) piece of double-sided tape was cut, one side was adhered to a glass slide, and the other side was evenly covered with pyrite powder. The pyrite powder sheet was sterilized by irradiating it under a UV lamp for 30 minutes before being added to seawater.

[0037] A control group and an experimental group were set up, with three parallel groups in each group.

[0038] Experimental group samples: Pyrite powder tablets were placed in petri dishes containing sterile seawater, ensuring the seawater just submerged the pyrite powder tablets; a passivating agent was added to achieve a viable bacteria concentration of 5 x 10⁻⁶ in the bacterial seawater system. 5 cells / mL; After sealing the culture dish with sealing film, place it in a constant temperature shaker at 30℃ and 45rpm. Replace the seawater in the culture dish with fresh sterile seawater every 5 days. After 20 days, take out the pyrite powder tablets, rinse them in sterile water, and place them in wide-mouth bottles with an initial pH of 5 and 7, respectively, containing 500mL of 0.5% (v / v) H2O2 solution. After sealing with sealing film, place them in a shaker at 25℃ and 80rpm for 180 days. Regularly replenish the evaporated water with sterile ultrapure water.

[0039] Control group samples: Pyrite powder flakes were placed in wide-mouth bottles containing 500 mL of 0.5% (v / v) H2O2 solution with initial pH values ​​of 5 and 7, respectively. After sealing with sealing film, the bottles were placed in a shaker at 25℃ and 80 rpm for 180 days. The evaporated water was replenished periodically with sterile ultrapure water.

[0040] Leachate was collected from the experimental and control groups at days 2, 15, 30, 60, 100, and 180, respectively. The passivation performance of the samples was assessed by changes in Fe ion concentration and pH in the leachate. The biotoxicity of the leachate was assessed by irrigating Shanghai bok choy and onion seedlings with the leachate after 180 days.

[0041] The passivation status of pyrite powder flakes after 20 days is shown in the figure. Figure 1 and Figure 2 .Depend on Figure 1 It can be seen that the surface of the pyrite powder flakes has been completely passivated by Gibberella flavonoids. Figure 2 This indicates that the *Gibberella flavonoids* cells completely encapsulated the pyrite flakes, and that a large portion of the cells had died and calcified (red). Data on oxidative leaching over 180 days and pH changes in the leachate are shown below. Figure 3 Data shows that bio-passivated pyrite effectively resists oxidant erosion. The Fe content detected in the leaching solution of unpassivated pyrite is 300 times higher than that of the passivated pyrite leaching solution. Furthermore, the passivation layer exhibits good pH buffering performance, maintaining the pH of the leaching solution at around 7.5. Macroscopic images show a large amount of yellow iron precipitate in the leaching solution of unpassivated pyrite, indicating that the measured Fe content in the leaching solution is less than the actual Fe content leached. In the passivation group with an initial pH of 5, some pyrite is eroded and peeled off by the oxidant, either settling at the bottom of the bottle or adhering to the bottle wall. However, the Fe content detected in the leaching solution does not increase, indicating that the bio-passivating agent effectively passivates the pyrite particles. After irrigating Shanghai bok choy and onion seedlings with the 180-day leaching solution for 28 days, it was observed that the seedlings irrigated with the passivated pyrite leaching solution exhibited growth comparable to those irrigated with mineral water, while the seedlings irrigated with the unpassivated pyrite leaching solution showed growth inhibition in both types of seedlings (e.g., Figure 5 and Figure 6 As shown in the figure, this indicates that biological passivation does not produce toxicity to organisms.

[0042] Example 3 Characterization of the bio-organic-inorganic passivation layer on the pyrite surface

[0043] Pyrite is crushed and ground, and then sieved through a standard sieve to obtain pyrite powder with a particle size in the range of 43-74μm. Before being added to seawater, the pyrite powder needs to be sterilized by irradiating it under an ultraviolet lamp for 30 minutes.

[0044] Experimental group sample: 0.2g of pyrite powder was placed in an Erlenmeyer flask containing 20mL of sterile seawater, and a passivating agent was added to make the viable bacteria concentration in the sterile seawater system 5 x 10⁻⁶. 5 cells / mL; After sealing the conical flask with sealing film, place it in a constant temperature shaker at 30℃ and 45rpm. Replace the seawater in the conical flask with fresh sterile seawater every 5 days. After 20 days of culture, use a pipette to aspirate the pyrite powder into the centrifuge tube, wash it 3 times with sterile pure water, and then put it in a drying oven at 60℃ to dry.

[0045] Depend on Figure 7 It can be seen that after 20 days, the surface of the pyrite particles was completely covered by a passivation layer. Fourier transform infrared spectroscopy was used to analyze the chemical composition of the passivation layer on the surface of the pyrite powder, and the results are as follows: Figure 8 As shown, a total of 9 peaks appear in the spectrum, among which the peak at 2520 cm⁻¹ is the highest. -1 CH2 in the corresponding amino acid, 1632cm -1 Corresponding CO in polysaccharides, 415 cm -1 Corresponding to SS in pyrite, 1781 cm -1 1490cm -1 1082cm -1 854cm -1 713cm -1 and 700cm -1 The calcium carbonate corresponds to the aragonite structure. Therefore, it is confirmed that the passivation layer on the surface of pyrite powder contains organic matter and calcium carbonate with an aragonite structure.

[0046] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A passivation method for bio-passivating agents used to passivate metal sulfide ore tailings, characterized in that, The bio-passivating agent is a culture containing marine calcified microorganisms; the method includes the following steps: The biological passivating agent is added to seawater at a ratio of at least 1:100; The metal sulfide tailings are immersed in seawater containing the biological passivating agent for no less than 20 days to form an organic-inorganic passivation layer with an aragonite structure on the surface of the metal sulfide tailings. The organic-inorganic passivation layer with aragonite structure is a composite passivation film of calcium carbonate with aragonite structure and bacteria. The marine calcifying microorganism is *Gibberella flavogenes*. The pH value of the seawater system is 7.0–8.5; The bio-passivating agent is used at temperatures between 15 and 37°C.

2. The passivation method for bio-passivating agent used to passivate metal sulfide tailings according to claim 1, characterized in that, In the bio-passivating agent, the viable bacterial concentration of the marine calcifying microorganisms is not less than 10. 8 cells / mL.

3. The passivation method for bio-passivating agent used to passivate metal sulfide ore tailings according to claim 2, characterized in that, The concentration of the marine calcifying microorganisms in the bio-passivating agent is 10. 9 ~10 10 cells / mL.

4. The passivation method for bio-passivating agent used to passivate metal sulfide tailings according to claim 1, characterized in that, The bio-passivating agent is used at a temperature of 25-37℃.

5. The passivation method for bio-passivating agent used to passivate metal sulfide ore tailings according to claim 1, characterized in that, The metal sulfide tailings include at least one of pyrite, chalcopyrite, and sphalerite waste rock.

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