A method for treating acid mine drainage by biopassivation of sulphide-containing mine waste rock source

Abstract

The application discloses a method for treating acid mine drainage by biopassivation of sulfur-containing mine waste rock at a source, and belongs to the field of mine environment treatment. The method comprises the following steps: using acidophilic microorganisms to induce an external iron source to form a passivation film on the surface of the sulfur-containing mine waste rock, so as to isolate oxygen, water and microorganisms from the sulfur-containing mine waste rock, and reduce the generation of acid mine drainage. The external iron source is widely available, the whole process is simple to operate, and the cost is low. The method can inhibit the biological / chemical dissolution of the sulfur-containing mine waste rock, and reduce the generation of acid mine drainage at a source, and therefore, has important significance for source treatment of acid mine drainage in coal mines and non-ferrous metal mines.

Description

Technical Field

[0001] This invention belongs to the field of mine environmental management, specifically relating to a method for treating acidic mine wastewater at its source by biological passivation of sulfide-containing mineral waste rock. Background Technology

[0002] The mining of sulfide ores leads to the generation of acid mine wastewater (AMD), characterized by extremely low pH (pH < 3) and high concentrations of harmful heavy metals (such as Cd, Cu, Fe, Mn, Pb, and Zn) and toxic metals (such as As and Se). AMD is a global environmental problem faced by mining companies and environmental protection departments. Untreated AMD discharged into the aquatic environment causes acidification and heavy metal pollution of nearby water bodies and farmland, ultimately posing a threat to animal and human health through the food chain.

[0003] Currently, it is believed that AMD formation is mainly related to sulfide minerals, especially pyrite. Pyrite is the most widely distributed sulfide mineral in the Earth's crust, and it is usually associated with other minerals such as copper sulfide, lead-zinc sulfide, or coal. Recent research on AMD remediation has focused on source control. Passivation is one method for source control of AMD. Its principle is to generate a passivation layer on the surface of pyrite to block its contact with oxygen, water, and microorganisms, thereby inhibiting its dissolution and reducing AMD release. However, the passivation agents currently developed domestically and internationally are mainly based on organic matter, phosphates, and silicates, which can easily cause eutrophication and secondary pollution. Furthermore, the passivation effect is greatly affected by the environment and is unstable.

[0004] Therefore, this invention synthesizes a passivation film on the surface of sulfide-containing waste rock such as pyrite through the induction of acidophilic microorganisms, which can make up for the shortcomings of the existing technology and carry out source treatment of AMD in a low-carbon, green and efficient manner, which is of great significance for the environmental management and protection of mining areas. Summary of the Invention

[0005] The purpose of this invention is to passivate sulfide-containing waste rock to reduce the generation of acidic mine wastewater at its source. A method for biological passivation of sulfide-containing waste rock for the source treatment of acidic mine wastewater has been developed. This method can overcome the shortcomings of existing passivation methods, reduce the amount of conventional passivation agents used, lower costs, and avoid secondary pollution and eutrophication of water bodies.

[0006] The objective of this invention is achieved through the following means:

[0007] A method for treating acidic mine wastewater at its source by biological passivation of sulfide-containing mineral waste rock involves using acidophilic microorganisms to induce the formation of a passivation film on the surface of sulfide-containing mineral waste rock by adding an external iron source.

[0008] The method for treating acidic mine wastewater by using biological passivation of sulfide-containing waste rock includes at least one of pyrite, chalcopyrite, bornite, and arsenopyrite waste rock, especially tailings or waste ore after flotation of sulfide ore.

[0009] The method for treating acidic mine wastewater at its source using biological passivation of sulfide-containing mineral waste rock includes at least one of the following acidophilic microorganisms: *Thiobacillus ferrooxidans*, *Thiobacillus thiooxidans*, *Thiobacillus thermophilus*, and *Leptospira ferrooxidans*.

[0010] The method for treating acidic mine wastewater by biological passivation of sulfide-containing mineral waste rock includes an additional iron source of at least one of ferrous sulfate, ferric sulfate, and iron ions in the acidic mine wastewater, with ferrous sulfate being more preferred.

[0011] The method for treating acidic mine wastewater at its source using biological passivation of sulfide ore waste rock requires that the concentration of the added iron source in the slurry be no less than 10 mmol / L, and more preferably 10~80 mmol / L.

[0012] The method for treating acidic mine wastewater by biological passivation of sulfide-containing mineral waste rock includes an external cation source of at least one of potassium sulfate, sodium sulfate, and ammonium sulfate, with potassium sulfate being more preferred.

[0013] The method for treating acidic mine wastewater by biological passivation of sulfide-containing mineral waste rock shall have an added cation source concentration of not less than 1 / 6 of the added iron source concentration.

[0014] The method for treating acidic mine wastewater at its source using biological passivation of sulfide-containing mineral waste rock requires an initial inoculum of acidophilic microorganisms of not less than 1×10⁻⁶. 8 Cells / mL, preferably 1×10 8 ~9×10 8 The concentration of the sample is 10-40°C, the pH is 2.5-3.5, the temperature is 10-40°C, the shaking speed is 100-200 r / min, and the biological passivation time is not less than 12 h, with a further optimized biological passivation time of 12-96 h.

[0015] A method for treating acidic mine wastewater at its source using biological passivation of sulfide-containing mineral waste rock, preferably comprising the following steps:

[0016] (1) Grind the sulfide-containing waste rock to -74μm or more using a vibratory mill.

[0017] (2) First, inoculate the acidophilic microbial culture at an inoculum rate of 5-20% into 100 mL of 9K medium for activation culture. The initial pH is 1.5-3.5, the temperature is 10-40 ℃, and the shaking speed is 100-200 r / min. Count the number of viable cells daily using a hemocytometer. When the bacterial concentration reaches 10... 8 ~10 9 Cells / mL, complete activation culture, and remove filter residue.

[0018] (3) Inoculate the activated acidophilic microorganisms at an inoculum size of 5-20% into 6 L of 9K medium for expansion culture. The initial pH is 1.5-3.5, the temperature is 10-40 ℃, and the shaking speed is 100-200 r / min. Count the number of viable cells daily using a hemocytometer. When the bacterial concentration reaches 10... 8 ~10 9 The bacterial culture was expanded to a concentration of 100 cells / mL. After removing the filter residue, the culture was centrifuged at high speed to obtain a concentrated bacterial solution free of metabolites.

[0019] (4) The inoculation dose is 1×10 8 ~9×10 8 Concentrated bacterial solution (number of bacteria per mL), iron source (10–80 mmol / L), and cation source (1 / 6–1 / 2 the concentration of iron source) were added to deionized water containing sulfide ore waste rock (0.5–5% slurry concentration) and pH 2.0–3.5. The mixture was then subjected to biopassivation for 12–96 h at a shaking speed of 100–200 r / min and a temperature of 10–40 °C.

[0020] (5) After biological passivation of sulfide mineral waste rock, filter paper is used to collect slag for surface morphology analysis, phase and elemental composition analysis, and biological and chemical oxidation of the biological passivated sulfide mineral waste rock to verify its stability.

[0021] This invention utilizes external iron and cation sources to induce the formation of a passivation film on the surface of sulfide-containing waste rock through the action of acidophilic microorganisms, thereby inhibiting sulfide dissolution and reducing the risk of AMD (Ammonium Acid Discharge) at its source. The entire process is low-cost, environmentally friendly, and economically beneficial. This invention is primarily applicable to the biological passivation of sulfide-containing waste rock and the source treatment of acidic mine wastewater. Attached Figure Description

[0022] Figure 1 This is a scanning electron microscope image of the biopassivation of pyrite-containing waste rock by *Acidithiobacillus ferrooxidans* induced by an external iron source (10 mmol / L) for 96 h in Example 1.

[0023] Figure 2 The figures show the total iron ion dissolution after 12 days of bioleaching (left) and chemical leaching (right) of pyrite-containing waste rock before and after biopassivation in Example 1.

[0024] Figure 3 This is a scanning electron microscope image of the biopassivation of pyrite-containing waste rock by *Acidithiobacillus ferrooxidans* induced by an external iron source (20 mmol / L) for 48 h in Example 2.

[0025] Figure 4 The figures show the total iron ion dissolution after 12 days of bioleaching (left) and chemical leaching (right) of pyrite-containing waste rock before and after biopassivation in Example 2.

[0026] Figure 5 This is a scanning electron microscope image of the biopassivation of pyrite-containing waste rock by *Thiobacillus acidophilus* induced by an external iron source (40 mmol / L) for 12 h in Example 3.

[0027] Figure 6 The figures show the total iron ion dissolution after 12 days of bioleaching (left) and chemical leaching (right) of pyrite-containing waste rock before and after biopassivation in Example 3.

[0028] Figure 7 This is a scanning electron microscope image of the biopassivation of chalcopyrite waste rock by *Acidithiobacillus ferrooxidans* induced by an external iron source (80 mmol / L) for 72 h in Example 4.

[0029] Figure 8 The copper ion dissolution of chalcopyrite waste rock before and after biopassivation in Example 4 is shown after 20 days of bioleaching. Detailed Implementation

[0030] The following specific embodiments or implementation methods are intended to further illustrate the present invention, and are not intended to limit the present invention. Example 1

[0031] The method described in this embodiment is mainly carried out according to the following steps:

[0032] (1) First, crush and dry grind the pyrite-containing waste rock, and then sieve it through a 200-mesh sieve to obtain a powder sample with a particle size of less than 74 μm.

[0033] (2) Inoculate 10% of the *Thiobacillus acidophilus* culture into 100 mL of 9K medium for activation culture. The initial pH was 2.0, the temperature was 30 °C, and the shaking speed was 170 r / min. The number of viable cells was counted daily using a hemocytometer. When the bacterial concentration reached 10... 8 Cells / mL, complete activation culture, and remove filter residue.

[0034] (3) The activated and cultured *Acidithiobacillus ferrooxidans* was inoculated at a rate of 5% into 6 L of 9K medium for expansion culture. The initial pH was 2.0, the temperature was 30 °C, and the shaking speed was 170 r / min. The number of viable cells was counted daily using a hemocytometer. When the bacterial concentration reached 10... 8 The bacterial culture was expanded to a concentration of 100 cells / mL. After removing the filter residue, the culture was centrifuged at high speed to obtain a concentrated bacterial solution free of metabolites.

[0035] (4) The inoculation dose is 4×10 8 A concentrated bacterial culture of *Thiobacillus acidophilus* (CFU / mL), 10 mmol / L ferrous sulfate, and 1.7 mmol / L potassium sulfate were added to deionized water containing pyrite slurry with a pH of 3.0 and subjected to biopassivation for 96 h at a shaking speed of 170 r / min and a temperature of 30 °C.

[0036] (5) After biological passivation of pyrite-containing waste rock, filter paper is used to collect slag for surface morphology analysis, phase and elemental composition analysis, and biological and chemical oxidation tests are conducted on the biological passivated pyrite-containing waste rock to verify its stability.

[0037] Result: As Figure 1 As shown, pyrite-containing waste rock without iron and cation sources developed numerous corrosion pits on its surface after 96 hours, while pyrite-containing waste rock treated with 10 mmol / L ferrous sulfate and 1.7 mmol / L potassium sulfate showed no corrosion pits and formed a protective layer after 96 hours. The initial pH was 3.0, and the initial concentration of *Thiobacillus ferrooxidans* was 2 × 10⁻⁶. 7 A 12-day bio-oxidation experiment was conducted on unpassivated and passivated pyrite-containing waste rock under the conditions of 170 r / min, 1 mL / ml, and 30℃. The results showed that ( Figure 2 (Left) The iron ions dissolved from the bio-passivated pyrite-containing waste rock were reduced by approximately 66% compared to the unpassivated pyrite-containing waste rock. A 12-day chemical oxidation test was conducted on the unpassivated and passivated pyrite-containing waste rock at a rotation speed of 170 r / min, a temperature of 30℃, and an initial pH of 3.0 in a sulfuric acid system. Figure 2 (Right) The iron leaching of pyrite-containing waste rock after biopassivation using this method is reduced by 80% compared to unpassivated pyrite-containing waste rock. This demonstrates that this method can effectively resist the oxidative corrosion of pyrite-containing waste rock by chemicals and bacteria, greatly reducing the dissolution of pyrite and reducing the risk of AMD from the source. Example 2

[0038] The method described in this embodiment is mainly carried out according to the following steps:

[0039] (1) First, crush and dry grind the waste rock sample containing pyrite, and then sieve it through a 200-mesh sieve to obtain a powder sample with a particle size of less than 74 μm.

[0040] (2) Inoculate 10% of the *Thiobacillus acidophilus* culture into 100 mL of 9K medium for activation culture. The initial pH was 2.0, the temperature was 30 °C, and the shaking speed was 170 r / min. The number of viable cells was counted daily using a hemocytometer. When the bacterial concentration reached 10... 8 Cells / mL, complete activation culture, and remove filter residue.

[0041] (3) The activated and cultured *Acidithiobacillus ferrooxidans* was inoculated at a rate of 5% into 6 L of 9K medium for expansion culture. The initial pH was 2.0, the temperature was 30 °C, and the shaking speed was 170 r / min. The number of viable cells was counted daily using a hemocytometer. When the bacterial concentration reached 10... 8 The bacterial culture was expanded to a concentration of 100 cells / mL. After removing the filter residue, the culture was centrifuged at high speed to obtain a concentrated bacterial solution free of metabolites.

[0042] (4) The inoculation dose is 6×10 8 A concentrated bacterial culture of *Thiobacillus acidophilus* (CFU / mL), 20 mmol / L ferrous sulfate, and 3.3 mmol / L potassium sulfate were added to deionized water containing pyrite slurry with a pH of 3.0 and subjected to biopassivation for 48 h at a shaking speed of 170 r / min and a temperature of 30 °C.

[0043] (5) After the pyrite-containing waste rock is biologically passivated, the slag is collected by filter paper for surface morphology analysis, phase and elemental composition analysis, and biological oxidation and chemical oxidation tests are conducted on the biologically passivated pyrite-containing waste rock to verify its stability.

[0044] Result: As Figure 3 As shown, pyrite-containing waste rock without iron and cation sources developed numerous corrosion pits on its surface after 48 hours, while pyrite-containing waste rock treated with 20 mmol / L ferrous sulfate and 3.3 mmol / L potassium sulfate showed no corrosion pits and formed a protective layer after 48 hours. The initial pH was 3.0, and the initial concentration of *Thiobacillus ferrooxidans* was 2 × 10⁻⁶. 7 A 12-day bio-oxidation experiment was conducted on unpassivated and passivated pyrite-containing waste rock under the conditions of 170 r / min, 1 mL / ml, and 30℃. The results showed that ( Figure 4(Left) The iron ion content of pyrite-containing waste rock after bio-passivation was reduced by approximately 73% compared to that of unpassivated pyrite-containing waste rock. A 12-day chemical oxidation test was conducted on unpassivated and passivated pyrite-containing waste rock at a rotation speed of 170 r / min, a temperature of 30℃, and an initial pH of 3.0 in a sulfuric acid system. The results showed... Figure 4 (Right) The iron leaching of pyrite-containing waste rock after biopassivation using this method is reduced by 84% compared to unpassivated pyrite-containing waste rock. This demonstrates that this method can effectively resist the oxidative corrosion of pyrite-containing waste rock by chemicals and bacteria, greatly reducing the dissolution of pyrite and reducing the risk of AMD from the source. Example 3

[0045] The method described in this embodiment is mainly carried out according to the following steps:

[0046] (1) First, crush and dry grind the waste rock sample containing pyrite, and then sieve it through a 200-mesh sieve to obtain a powder sample with a particle size of less than 74 μm.

[0047] (2) Inoculate 10% of the *Thiobacillus acidophilus* culture into 100 mL of 9K medium for activation culture. The initial pH was 2.0, the temperature was 30 °C, and the shaking speed was 170 r / min. The number of viable cells was counted daily using a hemocytometer. When the bacterial concentration reached 10... 8 Cells / mL, complete activation culture, and remove filter residue.

[0048] (3) The activated and cultured *Acidithiobacillus ferrooxidans* was inoculated at a rate of 5% into 6 L of 9K medium for expansion culture. The initial pH was 2.0, the temperature was 30 °C, and the shaking speed was 170 r / min. The number of viable cells was counted daily using a hemocytometer. When the bacterial concentration reached 10... 8 The bacterial culture was expanded to a concentration of 100 cells / mL. After removing the filter residue, the culture was centrifuged at high speed to obtain a concentrated bacterial solution free of metabolites.

[0049] (4) The inoculation dose is 4×10 8 A concentrated bacterial culture of *Thiobacillus acidophilus* (CFU / mL), 40 mmol / L ferrous sulfate, and 6.6 mmol / L potassium sulfate were added to deionized water containing pyrite slurry with a pH of 3.0 and subjected to biopassivation for 12 h at a shaking speed of 170 r / min and a temperature of 30 °C.

[0050] (5) After the pyrite-containing waste rock is biologically passivated, the slag is collected by filter paper for surface morphology analysis, phase and elemental composition analysis, and biological oxidation and chemical oxidation tests are conducted on the biologically passivated pyrite-containing waste rock to verify its stability.

[0051] Result: As Figure 5As shown, pyrite-containing waste rock without iron and cation sources showed numerous corrosion pits on its surface after 12 hours, while pyrite-containing waste rock treated with 40 mmol / L ferrous sulfate and 6.6 mmol / L potassium sulfate showed no corrosion pits and formed a "protective layer" after 12 hours. The initial pH was 3.0, and the initial concentration of *Thiobacillus ferrooxidans* was 2 × 10⁻⁶. 7 A 12-day bio-oxidation experiment was conducted on unpassivated and passivated pyrite-containing waste rock under the conditions of 170 r / min, 1 mL / ml, and 30℃. The results showed that ( Figure 6 (Left) The amount of iron ions dissolved from pyrite-containing waste rock after bio-passivation was reduced by approximately 33% compared to unpassivated pyrite-containing waste rock. A 12-day chemical oxidation test was conducted on unpassivated and passivated pyrite-containing waste rock at a rotation speed of 170 r / min, a temperature of 30℃, and an initial pH of 3.0 in a sulfuric acid system. The results showed... Figure 6 (Right) The iron leaching of pyrite-containing waste rock after biopassivation using this method is reduced by 30% compared to unpassivated pyrite-containing waste rock. This demonstrates that this method can effectively resist the oxidative corrosion of pyrite-containing waste rock by chemicals and bacteria, reduce the dissolution of pyrite, and reduce the risk of AMD from the source. Example 4

[0052] The method described in this embodiment is mainly carried out according to the following steps:

[0053] (1) First, crush and dry grind the chalcopyrite waste rock sample, and then sieve it through a 200-mesh sieve to obtain a powder sample with a particle size of less than 74 μm.

[0054] (2) The *Leptospira acidophilus* bacterial suspension was inoculated at a rate of 10% into 100 mL of 9K medium for activation culture. The initial pH was 2.0, the temperature was 45 ℃, and the shaking speed was 180 r / min. The number of viable cells was counted daily using a hemocytometer. When the bacterial concentration reached 10... 8 Cells / mL, complete activation culture, and remove filter residue.

[0055] (3) The activated and cultured Leptospira acidophilus was inoculated at a rate of 5% into 6 L of 9K medium for expansion culture. The initial pH was 2.0, the temperature was 45 ℃, and the shaking speed was 180 r / min. The number of viable cells was counted daily using a hemocytometer. When the bacterial concentration reached 10... 8 The bacterial culture was expanded to a concentration of 100 cells / mL. After removing the filter residue, the culture was centrifuged at high speed to obtain a concentrated bacterial solution free of metabolites.

[0056] (4) The inoculation dose is 5×10 8Concentrated Leptospira acidophilus culture (number / mL), 80 mmol / L ferrous sulfate, and 13.3 mmol / L potassium sulfate were added to deionized water containing chalcopyrite waste rock with a slurry concentration of 2% and a pH of 2.5. The mixture was then subjected to biopassivation for 72 h at a shaking speed of 180 r / min and a temperature of 45 °C.

[0057] (5) After the chalcopyrite waste rock was biopassivated, the slag was collected by filter paper for surface morphology analysis, phase and elemental composition analysis, and bio-oxidation test was conducted on the biopassivated chalcopyrite waste rock to verify its stability.

[0058] Result: As Figure 7 As shown, chalcopyrite waste rock without added iron and cation sources showed obvious corrosion pits on its surface after 72 hours, while chalcopyrite waste rock treated with 80 mmol / L ferrous sulfate and 13.3 mmol / L potassium sulfate showed no corrosion pits on its surface after 72 hours and formed a "protective layer". The initial pH was 2.0, and the initial concentration of *Thiobacillus ferrooxidans* was 3 × 10⁻⁶. 7 A 20-day bio-oxidation experiment was conducted on unpassivated and passivated chalcopyrite waste rock under the conditions of 170 r / min, 1 mL / ml, and 30℃. The results showed that ( Figure 8 The copper ion leaching from chalcopyrite-containing waste rock after biopassivation was reduced by approximately 65% ​​compared to unpassivated chalcopyrite-containing waste rock. This indicates that the method can effectively resist bacterial oxidative corrosion of chalcopyrite-containing waste rock, greatly reducing copper pollution caused by the biodissolution of chalcopyrite and reducing the risk of AMD from the source.

Claims

1. A method for the abatement of acid mine drainage from a sulphidic mine waste rock source by biopassivation, characterised in that: The method comprises the following steps: generating a passivation film on the surface of the waste rock containing sulfide ore by using acidophilic microorganisms to induce an additional iron source and a cation source; the additional iron source is ferrous sulfate; the concentration of the additional iron source in the waste rock containing sulfide ore is not less than 10 mmol / L; the additional cation source is potassium sulfate, sodium sulfate and ammonium sulfate; the concentration of the additional cation source is not less than 1 / 6 of the concentration of the additional iron source. Specific is inoculated with not less than 1 x 10 8 acidophilic microorganisms into the ore pulp concentration of 1-5% containing sulfide ore waste rock biological passivation system, biological passivation system initial pH 2.5-3.5, temperature is 10-40℃, the speed of the shaker is 100-200r / min; biological passivation time is not less than 12h.

2. A method of acid mine drainage abatement at the source by bio-passivation of sulphidic mine waste rock according to claim 1, characterised in that: The waste rock containing sulfide ore comprises at least one of waste rock containing pyrite, chalcopyrite, bornite and arsenopyrite.

3. A method of acid mine drainage abatement at the source by bio-passivation of sulphidic mine waste rock according to claim 2, characterised in that: The waste rock containing sulfide ore comprises tailings or abandoned ore after flotation of sulfide ore.

4. The method of bio-passivating pyritic mine waste rock source head treatment of acid mine drainage of claim 1, wherein: The acidophilic microorganisms comprise at least one of acidophilic ferrous-oxidizing Thiobacillus, acidophilic sulfur-oxidizing Thiobacillus, acidophilic thermophilic Thiobacillus and acidophilic ferrous-oxidizing Leptospirillum.

5. The method for controlling acid mine drainage from sulphidic mine waste rock sources at the headwaters according to any one of claims 1 to 4, characterised in that: The waste rock containing sulfide ore is crushed and sieved to a particle size of less than 74 microns before being passivated.

Images