Method for treating mine wastewater by driving in-situ self-assembly Bio-FeS (at) SRB by weak current

Abstract

The invention discloses a method for treating mine wastewater by driving in-situ self-assembly Bio-FeS (at) SRB through weak current, and belongs to the technical field of wastewater treatment. The method comprises the following steps: (1) constructing a weak current driven electrolysis system; an anode in an anode chamber and a cathode in a cathode chamber of the weak current driven electrolysis system are connected with a direct-current power supply through wires to form a current loop; (2) adding organic wastewater and artificial water into an anode chamber of the weak-current-driven electrolysis system, and adding simulated mine wastewater and SRB bacterial liquid into a cathode chamber of the weak-current-driven electrolysis system; applying a voltage of 0.4-1.0 V between the anode and the cathode by using a direct-current power supply; in the process of applying the voltage, carrying out in-situ self-assembly on a Bio-FeS (at) SRB heterozygote on the surface of the cathode electrode; and (3) adding to-be-treated mine wastewater into a cathode chamber of the electrolysis system, and applying voltage, so that sulfate and heavy metals in the wastewater can be synchronously removed in the treatment process. According to the method, the Bio-FeS (at) SRB is formed, so that the sulfate radicals and the heavy metal ions in the mine wastewater can be efficiently and synchronously removed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, in particular to a method for treating mine wastewater by weak electric driving in-situ self-assembly Bio-FeS@SRB. BACKGROUND

[0002] Mine wastewater, especially acid mine drainage (AMD), is a strong acidic wastewater formed by the oxidation, decomposition and reaction with water of sulfide minerals in the process of mining, transportation, ore dressing, waste rock stacking and tailings storage of sulfide ore deposits. Its typical characteristics include: (1) high sulfate concentration; (2) strong acidity; (3) rich in heavy metal ions; (4) low organic matter content, lack of easily biodegradable organic carbon source. If such wastewater is discharged directly without treatment, it will cause large-scale acid and heavy metal pollution, seriously damage water ecology, pollute soil, corrode infrastructure, and ultimately threaten human health. Therefore, it is crucial to develop efficient, economical and environmentally friendly AMD treatment technology.

[0003] Physical and chemical methods (such as neutralization precipitation, adsorption, membrane separation, etc.) generally have high investment and operating costs, are prone to produce a large amount of heavy metal-containing sludge that needs to be safely disposed of (secondary pollution risk), and have unstable treatment effect (especially for complex multi-metal systems), which is difficult to meet the demand of large-scale and sustainable treatment. Microbial treatment of mine wastewater refers to the process in which sulfate-reducing bacteria (SRB) convert SO4 2- in wastewater into S 2- by its own metabolism, S 2- can generate insoluble sulfide precipitates with heavy metal ions, achieving simultaneous removal of SO4 2- and heavy metals, and the SRB metabolic process also produces alkalinity to raise the pH of the wastewater. However, the organic matter content in mine wastewater is low, making it difficult to provide sufficient electron donors for SRB growth and metabolism, and the multiple heavy metals in mine wastewater can cause toxic effects on SRB, affecting its treatment effect. SUMMARY

[0004] Based on the above technical problems, the present application provides a method for treating mine wastewater by weak electric driving in-situ self-assembly Bio-FeS@SRB.

[0005] The technical solution adopted by the present application is: A method for treating mine wastewater by weak electric driving in-situ self-assembly Bio-FeS@SRB, comprising the following steps: (1) Construct a weak electric driving electrolysis system; The weak current driven electrolysis system comprises a reaction tank, an exchange membrane arranged in the reaction tank, the exchange membrane separating the reaction tank into an anode chamber and a cathode chamber, an anode arranged in the anode chamber, a cathode arranged in the cathode chamber, and a reference electrode arranged in the anode chamber and the cathode chamber; the anode and the cathode are connected with a direct current power supply through wires to form a current loop; A resistor is connected in series on the wire, and a data collector is connected at both ends of the resistor, for recording the voltage at both ends of the resistor in real time; (2) In-situ self-assembly of Bio-FeS@SRB hybrid at the cathode of the weak current driven electrolysis system; Organic wastewater and artificial water are added to the anode chamber of the weak current driven electrolysis system to form an anode liquid; simulated mine wastewater and SRB bacterial liquid are added to the cathode chamber of the weak current driven electrolysis system to form a cathode liquid; A voltage of 0.4-1.0 V is applied between the anode and the cathode by using a direct current power supply; During the application of the voltage, the SRB bacterial liquid in the cathode chamber reduces the iron source in the simulated mine wastewater to generate ferrous sulfide (FeS) nanoparticles in-situ, which spontaneously coat the surface of the SRB cells to form a Bio-FeS@SRB hybrid; The ferrous sulfide nanoparticles in the Bio-FeS@SRB hybrid can reduce the sulfate in the simulated mine wastewater to produce hydrogen sulfide (H2S) and water (H2O) in-situ; , The ferrous sulfide nanoparticles in the Bio-FeS@SRB hybrid can also react with the iron source in the simulated mine wastewater to generate ferrous sulfide (FeS) nanoparticles in-situ, which spontaneously coat the surface of the SRB cells to form a Bio-FeS@SRB hybrid; (3) Mine wastewater treatment; Artificial water is added to the anode chamber of the weak current driven electrolysis system, and the mine wastewater to be treated is added to the cathode chamber, a voltage of 0.4-1.0 V is applied between the anode and the cathode by using a direct current power supply, and the sulfate and heavy metals in the mine wastewater to be treated can be removed synchronously during the treatment.

[0006] Preferably, in step (1), the anode and the cathode are both carbon fiber brushes; before use, the carbon fiber brushes are soaked in an acetone solution for more than 12 h, then washed with deionized water, and then calcined in a muffle furnace at 450-500℃ for 20-30 min; The reference electrode is an Ag / AgCl electrode, the lower part of the reference electrode is arranged below the liquid level in the anode chamber or the cathode chamber, and the vertical distance between the reference electrode and the anode or the cathode is ≤2 cm.

[0007] Preferably, in step (2), the anode liquid contains an anode bacterial strain, and the anode bacterial strain is derived from organic wastewater and / or sludge; the organic wastewater can be domestic wastewater, papermaking, food processing and other industrial wastewater and / or aquaculture wastewater, the COD content of the organic wastewater is 200-8000 mg / L, and the pH is 6.5-8.5; the sludge is selected from the anaerobic digestion tank of a municipal domestic wastewater treatment plant, the mixed liquid suspended solid concentration (MLSS) of which is 20000-40000 mg / L, and the pH is 7.0-7.2.

[0008] Preferably, in step (2), the concentration of sodium acetate in the artificial water is 1.0 g / L, the concentration of the phosphate buffer solution is 50 mmol / L, and the pH value is 7.0-7.5. The phosphate buffer solution contains 0.31 g / L of NH4Cl, 0.13 g / L of KCl, 3.32 g / L of NaH2PO4·2H2O, and 10.32 g / L of Na2HPO4·12H2O.

[0009] Preferably, in step (2), the SRB bacterial solution uses anaerobic sludge from a digestion tank of a sewage treatment plant as a bacterial source, and uses a conventional culture medium such as modified Postgate's C culture medium for subculture and enrichment of the SRB bacterial population.

[0010] Preferably, in step (2), the simulated mine wastewater contains SO4 2– 600-5000 mg / L, Fe 2+ 200-3000 mg / L, and the pH value is 6.0-7.5.

[0011] Preferably, in step (2), the anolyte and the catholyte are replaced once every 24-72 hours; the current response change is recorded by a data collector; when the removal rate of sulfide in the catholyte is stably above 70% and the removal rate fluctuation of adjacent batches is less than 5% in three consecutive batches, and the current-time curve presents a stable and repeatable rising and plateau feature, the inoculation is considered to be completed.

[0012] Preferably, in step (3), the concentration of sodium acetate in the artificial water is 1.0 g / L, the concentration of the phosphate buffer solution is 50 mmol / L, and the pH value is 7.0-7.5. The treated domestic wastewater is introduced into the anode chamber, so that the domestic wastewater is treated synchronously in the process of treating the mine wastewater. The main purpose of treating the domestic wastewater is to reduce the chemical oxygen demand (COD) and also to partially remove nitrogen-containing pollutants. Before entering the anode chamber, the treated domestic wastewater is filtered to remove suspended solids (SS). Similarly, the treated mine wastewater can also be filtered to remove suspended solids before entering the cathode chamber. In addition, if the mine wastewater is too acidic (pH < 5), the pH thereof needs to be adjusted to above 5.0 in advance to avoid the inhibitory effect of the strong acidic environment on the bacteria in the cathode chamber and to ensure the metabolic activity of the microorganisms.

[0013] The beneficial technical effects of the present application are: ​The application is driven by weak electricity through the constructed electrolysis system, 0.4-1.0 V voltage is applied between the anode and the cathode, the surface in-situ self-assembly of nano ferrous sulfide particles of sulfate reducing bacteria (SRB) is promoted, the Bio-FeS@SRB hybrid is formed, and the unique properties of the hybrid are utilized to realize the efficient and synchronous removal of sulfate ions (SO42-) ) and heavy metal ions in mine wastewater, and the method has the advantages of low operation cost.

[0014] Specifically, the following aspects are embodied: (1) The Bio-FeS@SRB hybrid (Bio in the hybrid represents biology, that is, FeS synthesized under the action of biology) formed by the immobilization of sulfate reducing bacteria (SRB) and nano ferrous sulfide (FeS NPs) on the surface of the cathode realizes the efficient coupling of biological metabolic network and electrochemical interface. The method relies on the biological catalytic activity of SRB and the electron-mediated ability of FeS NPs, and cooperatively drives the sulfate reduction and heavy metal reduction / removal of the cathode, significantly improves the synchronous removal efficiency of the combined pollutants in the mine wastewater. The method not only significantly improves the removal rate of sulfate ions and heavy metal ions, but also realizes the doubling of the electron transfer rate through the in-situ regeneration of FeS NPs, and provides a low-energy-consumption, high-compatibility green solution for the treatment of mine wastewater.

[0015] (2) The and in the mine wastewater can be used as a natural raw material bank, and the metabolized by the exogenous added SRB combines with the wastewater to generate FeS NPs, and forms a protective layer on the surface of the bacteria to obtain the Bio-FeS@SRB hybrid. In view of the pain point of the lack of organic matter in the wastewater, the electrons generated by the oxidation of organic matter on the anode of the electrolysis system are directionally transported to the SRB through the external circuit, and the cathode replaces the traditional carbon source as the electron donor of the SRB to activate the sulfate reduction activity thereof; the in the wastewater is reduced to on the cathode, the yield of FeS NPs is improved, and a positive feedback cycle of “electron transfer acceleration-FeS proliferation-pollutant degradation enhancement” is formed.

[0016] (3) The FeS NPs coated on the surface of the SRB effectively block the direct cytotoxicity of heavy metal ions such as copper, chromium and zinc; the SRB reduces to by using the cathode electrons; the generated is combined with the heavy metal ions to form stable precipitates, and the removal of the heavy metals and the recovery of sulfur are realized synchronously, thereby blocking the risk of secondary pollution from the source. BRIEF DESCRIPTION OF DRAWINGS ​

[0017] Figure 1 The structural schematic diagram of the weak electric driving electrolysis system constructed in the weak electric driving in-situ self-assembly Bio-FeS@SRB method for treating mine wastewater of the present application; Figure 2 The SEM-EDS diagram of the Bio-FeS@SRB hybrid obtained in the present application; wherein a is the SEM diagram of SRB, b is the SEM diagram of the Bio-FeS@SRB hybrid, and c is the element distribution diagram of S and Fe in the Bio-FeS@SRB hybrid; Figure 3 The XRD spectrum diagram of the Bio-FeS@SRB hybrid obtained in the present application; Figure 4 The Bio-FeS@SRB hybrid is added into the cathode chamber of the electrolysis system of the present application 2+ The output current density curves before and after; Figure 5a The removal rates of the Bio-FeS@SRB hybrid and SRB in the method of the present application for different concentrations of Cr(VI); Figure 5b The removal rates of Cr(VI) of the Bio-FeS@SRB hybrid and SRB in the method of the present application for different concentrations of Cr(VI); Figure 6 The removal rates of heavy metals Cu(II), Zn(II), Pb(II) and Cd(II) of the Bio-FeS@SRB hybrid and SRB in the method of the present application; Figure 7 The output current density change diagram of the electrolysis system under different voltage intensities; Figure 8 The SEM pictures and size distribution diagrams of the nano-FeS formed by the cathode of the electrolysis system under different voltage intensities; wherein a is the SEM diagram of the Bio-FeS@SRB hybrid formed by the cathode under different voltage intensities, and b is the particle size statistical diagram of the nano-FeS particles formed under the corresponding voltage; Figure 9 The removal effects of Cr(VI) of the electrolysis system under different voltage intensities; Figure 10 The influence of the Bio-FeS@SRB hybrid on the removal rate of Cr(VI) in the SRB bacterial solution without applying external voltage; The influence of the Bio-FeS@SRB hybrid on the removal rate of Cr(VI) in the SRB bacterial solution when applying 0.8 V external voltage. Figure 11 The influence of the Bio-FeS@SRB hybrid on the removal rate of Cr(VI) in the SRB bacterial solution when applying 0.8 V external voltage.

[0018] Figure 1 ​​In the diagram: 1-Anode chamber, 2-Cathode chamber, 3-Exchange membrane, 4-Anode, 5-Cathode, 6-Reference electrode, 7-Wire, 8-DC power supply, 9-Fixed resistor, 10-Data acquisition unit. Detailed Implementation

[0019] Addressing the long-standing core challenges in mine wastewater treatment, such as "low organic matter inhibiting SRB," "heavy metal toxicity," "high cost," and "risk of secondary pollution," this invention proposes a weakly electrically driven in-situ self-assembly method for treating mine wastewater using Bio-FeS@SRB. This method not only effectively removes heavy metals and sulfates from acidic mine wastewater (AMD), but also fully utilizes the abundant Fe content in AMD itself. 2+ and SO4 2- Due to its unique characteristics, Bio-FeS@SRB spontaneously forms. By using an electrolysis system to provide electrons, the addition of a carbon source is eliminated, which greatly reduces costs and produces no secondary pollution. It has significant environmental and economic benefits and demonstrates broad application potential.

[0020] The core advantages of this invention are reflected in the following aspects: First, creatively utilize the Fe content abundant in mine wastewater. 2+ and SO4 2- During SRB metabolism, a complex with specific structure and function, Bio-FeS@SRB, is spontaneously formed. This is the key difference from traditional SRB applications. Traditional methods require an external iron source (such as...). FeS precipitates are generated to remove pollutants. However, this invention eliminates the need for an additional Fe source, directly utilizing components in wastewater to achieve in-situ, self-assembly synthesis of FeS nanoparticles (FeS NPs) and tight coating of them onto SRB. This promotes electron exchange between the SRB and the external environment (such as electrodes or other electron acceptors / donors), enhancing the overall reaction rate. This significantly reduces costs, simplifies the operation process, and improves the system's self-sufficiency and environmental friendliness.

[0021] Secondly, because the organic matter content in mine wastewater is extremely low, existing methods for treating mine wastewater using SRB generally require the addition of an additional carbon source to provide the electron donors needed for the reaction. This invention, however, utilizes the weak current generated by the electrolysis system (or the current generated at the cathode)... ), to provide its restoration for SRB The required electron donor solves the problem of electron donor scarcity in mine wastewater, significantly improving SRB activity and sulfate reduction efficiency. Furthermore, by utilizing the cathode reduction capability of the electrolysis system, the wastewater... High efficiency to This not only recycles materials that might otherwise have been lost due to sedimentation. More importantly, it increased the availability of The concentration of FeS is increased, thereby promoting the formation of more Bio-FeS@SRB and improving overall treatment efficiency (especially heavy metal removal) and electron transfer efficiency. Simultaneously, the voltage intensity control of the electrolysis system allows for the directional synthesis of FeS NPs, improving coverage uniformity and ensuring SRB activity.

[0022] Finally, compared to traditional SRB, Bio-Fes@SRB, with its surface coated with FeS NPs particles, can physically isolate and chemically adsorb SRB, significantly reducing the direct toxicity of heavy metal ions to SRB cells and decreasing harmful gases. To reduce emissions and avoid secondary pollution.

[0023] The present invention proposes a method for treating mine wastewater by in-situ self-assembly of Bio-FeS@SRB driven by weak current, comprising the following steps: (1) Construct a weakly driven electrolysis system; like Figure 1 As shown, the weak current driven electrolysis system includes a reaction tank. An exchange membrane 3 is installed inside the reaction tank, dividing it into an anode chamber 1 and a cathode chamber 2. An anode 4 is installed in the anode chamber 1, and a cathode 5 is installed in the cathode chamber 2. Reference electrodes 6 are also installed in both the anode chamber 1 and the cathode chamber 2. Both the anode 4 and the cathode 5 are connected to a DC power supply 8 via wires 7, forming a current loop. A fixed resistor 9 is connected in series with the wires 7, and a data acquisition device 10 is connected across the fixed resistor 9 to record the voltage across the resistor in real time.

[0024] (2) In-situ self-assembly of Bio-FeS@SRB hybrids at the cathode of a weakly driven electrolysis system; Organic wastewater and artificially prepared water are added to the anode chamber of the weak-current driven electrolysis system to form the anolyte; simulated mine wastewater and SRB bacterial solution are added to the cathode chamber to form the catholyte. A voltage of 0.4~1.0 V is applied between the anode and cathode using a DC power supply. During the voltage application process, the SRB bacterial solution in the cathode chamber reduces the simulated mine wastewater... produce , The iron source reacts with the iron source in the simulated mine wastewater to generate ferrous sulfide nanoparticles in situ. These ferrous sulfide nanoparticles spontaneously coat the surface of SRB cells to form Bio-FeS@SRB hybrids.

[0025] (3) Treat mine wastewater; Artificial water is added to the anode chamber of the weak current driven electrolysis system, and the mine wastewater to be treated is added to the cathode chamber. A voltage of 0.4~1.0 V is applied between the anode and cathode through a DC power supply. During the treatment process, sulfates and heavy metals in the mine wastewater to be treated can be removed simultaneously.

[0026] In step (1) above: the configuration of the reaction tank includes, but is not limited to, H-type, cubic, and cylindrical.

[0027] The outer wall material of the anode chamber and cathode chamber includes, but is not limited to, one or more of glass, plexiglass (PMMA), polycarbonate (PC) and polyvinyl chloride (PVC). The effective volume of the chamber is 50 mL to 10 L. Sampling ports are provided in both the anode chamber and the cathode chamber for periodic water sample collection.

[0028] The electrode materials for the anode and cathode can be made of three types: carbon materials, metallic materials, and conductive polymer materials. Carbon materials include, but are not limited to, one or more of the following: carbon cloth, carbon felt, carbon brush, carbon nanotubes, graphene, graphite felt, graphite plates, graphite rods, graphite particles, granular activated carbon, and biochar. For example, if both the anode and cathode are made of carbon fiber brushes, before use, the carbon fiber brushes should be soaked in acetone solution for at least 12 hours, rinsed with deionized water, and then calcined in a muffle furnace at 450-500℃ for 20-30 minutes to enhance performance. Conductive metallic materials include, but are not limited to, one or more of the following: titanium wire, titanium mesh, titanium plate, stainless steel mesh, and nickel mesh, commonly used as electrode current collectors or supports. The electrodes can be cut into sheets, rolled into cylinders, or filled into a granular bed. The cathode and anode are usually placed parallel and facing each other, with a spacing of 1-20 cm. The electrodes are connected to the external circuit via titanium wires / leads, and silicone plugs are used to ensure a seal at the electrode leads.

[0029] The exchange membrane includes, but is not limited to, one of a proton exchange membrane (such as Nafion), a cation exchange membrane (such as CMI-7000), and an anion exchange membrane. A proton exchange membrane or a cation exchange membrane is preferred to ensure effective proton migration. The exchange membrane is tightly clamped between the anode and cathode chambers by flanges, sealing rings, or silicone sheets to ensure liquid isolation between the two chambers.

[0030] The anode and cathode are connected by an external circuit. The external circuit includes a fixed resistor (preferably 10 Ω) and a DC regulated power supply or a potentiostat. The potentiostat controls the cathode potential relative to the reference electrode within the range of -0.6 V to -1.2 V; alternatively, a regulated power supply applies a constant voltage of 0.4–1.0 V between the anode and cathode. A data acquisition unit is connected across the fixed resistor to record the voltage drop across the resistor in real time to calculate the loop current (I = V / R) or to directly record the current signal.

[0031] The reference electrode is positioned below the liquid level within the anode / cathode chamber, close to the anode / cathode surface. Preferably, the distance between the reference electrode and the anode or cathode is ≤2 cm to accurately monitor the electrode potential. The reference electrode includes, but is not limited to, a saturated calomel electrode or a silver / silver chloride electrode.

[0032] The cathode has an electrode surface and the liquid phase nearby where sulfate-reducing bacteria (SRB) attach and grow, reducing sulfate and producing sulfur. 2- and Fe in the wastewater 2+ The site where the reaction generates nano-ferrous sulfide (FeS NPs) in situ and then self-assembles to form the Bio-FeS@SRB hybrid.

[0033] In step (2) above: microorganisms are inoculated on both the anode and cathode. The anode microbial strains can be derived from, but are not limited to, one or more sources such as domestic sewage, activated sludge, anaerobic sludge, and river / lake sediment. Microorganisms with sulfate-reducing capabilities are inoculated on the cathode. The bacterial solution is a sulfate-reducing bacterial solution obtained from the enrichment and cultivation of anaerobic sludge, and the bacterial solution OD... 600 It is approximately 0.6 to 1.0.

[0034] During the inoculation phase, the anode uses a mixed solution of sewage or sludge and artificially prepared water, with a volume ratio of 10-60%. The artificially prepared water contains 1.0 g / L sodium acetate and 50 mmol / L phosphate buffer solution, with a pH of 7.0-7.5. The cathode uses a mixed solution of simulated mine wastewater (1000 mg / L Na2SO4, 1400 mg / L FeCl2·4H2O) and sulfate-reducing bacterial solution (SRB bacterial solution) (volume ratio of 1:1 to 4:1).

[0035] Replace the solutions in the anode and cathode chambers every 24–72 hours. Apply a voltage of 0.4–1.0 V to both the anode and cathode using a power supply (or control the cathode potential at -0.6 V to -1.2 V using a potentiostat). Record the current response changes using a data acquisition device across a fixed resistor. When three consecutive batches of catholyte are processed... When the removal rate is stable at over 70% and the fluctuation of the removal rate between adjacent batches is less than 5%, and the current-time curve shows a stable and repeatable upward and plateau characteristics, the inoculation is considered complete.

[0036] In step (3) above: during normal operation, artificially prepared water with sodium acetate as the main carbon source or domestic sewage is introduced into the anode chamber, and the COD concentration is maintained at 500-2000 mg / L. Mine wastewater to be treated is introduced into the cathode chamber, which contains... , and heavy metals such as Cr, Cu, Zn, and As, The concentration range is 600~5000 mg / L, the total iron concentration is 200~3000 mg / L, and the pH is 6.0-7.5. This stage can simultaneously remove sulfate and heavy metals from the mine wastewater to be treated. The operating cycle is 24~72 hours, with a sulfate removal rate of over 70% and a heavy metal removal rate of over 80%.

[0037] The core principle of this invention lies in utilizing the weak electrical drive (0.4~1.0V) of an electrolysis system or microbial electrolysis cell to synergistically promote the in-situ self-assembly of nano-ferrous sulfide particles (Bio-FeS@SRB) on the surface of sulfate-reducing bacteria (SRB), and leveraging the unique properties of this hybrid to achieve the reduction of sulfate in mine wastewater (… It achieves efficient, simultaneous, and economical removal of heavy metal ions. Its working principle can be divided into the following parts: (1) Weak current drive and electronic power supply; In the anode chamber of the electrolysis system, inoculated anolyte microorganisms (such as electrogenic bacteria) oxidize organic matter (such as organic matter in domestic sewage) in the anolyte, generating electrons (…). ) and proton ( Electrons flow towards the cathode through the external circuit under the drive of a weak applied voltage (0.4~1.0 V).

[0038] In the cathode chamber, electrons reaching the cathode are utilized through two main pathways: Direct electron transfer: Electrons are directly captured by SRB cells attached to the cathode surface, serving as their extracellular electron donors.

[0039] Indirect electron transfer ( Pathway: Electrons reduce protons in the water at the cathode surface ( ), producing hydrogen gas ( ) diffuses into the liquid phase and is utilized by SRB as an electron donor. ).

[0040] This process fundamentally solves the problem of traditional SRB treatment's strong dependence on organic carbon sources. The electrolysis system utilizes energy generated from inexpensive and readily available organic wastewater (such as domestic sewage) in the anode chamber, and through weak electrical drive, remotely and controllably delivers electrons to the cathode chamber, providing a stable and sufficient electron donor (directly) for the cathode SRB. or It significantly accelerates the sulfate reduction metabolism of SRB, and is especially suitable for mine wastewater with low COD (low organic matter).

[0041] (2) Biological reduction of sulfate and formation of sulfides: The SRB in the cathode chamber utilizes the electrons (or) provided above. During its metabolism, it removes sulfate ions from the wastewater ( ) is reduced to sulfide ions ( ).

[0042] (3) Iron ion conversion and in-situ synthesis of FeS NPs: Mine wastewater is typically rich in dissolved ferrous ions (Fe2+). ) and ferric ions ( The cathode of the electrolysis system not only supplies electrons to SRB, but also removes electrons from the wastewater. Directly restore to Sulfide ions produced by the reduction of SRB With wastewater (Including those from raw water and those generated by cathodic reduction) undergo a chemical reaction to produce sparingly soluble ferrous sulfide nanoparticles. This process makes full use of the iron resources abundant in the mine wastewater itself. No additional iron salts are needed; the iron form is controlled through the reduction action of the cathode. Furthermore, by utilizing the sulfides generated by SRB, highly reactive nano-FeS particles (FeS NPs) are synthesized in situ in the cathode chamber (mainly on and near the surface of SRB cells), thus realizing the resource utilization of "waste treatment".

[0043] (4) In-situ self-assembly and function of Bio-FeS@SRB hybrids: In-situ generated nano-FeS particles (FeS NPs) possess high surface energy and tend to adsorb and tightly coat the surface of the SRB cells that produce them, forming a unique sulfate-reducing bacterium-nano-ferrous sulfide hybrid (Bio-FeS@SRB). Its main functions are as follows: ① Enhanced electron transport: FeS NPs coated on the SRB surface are excellent electron conductors. They establish an artificial electron transport channel, transferring electrons from the extracellular environment (such as the cathode surface, solution, etc.) Extracellular electrons (or direct electrons) are more efficiently transported into the periplasm or cytoplasm of SRB cells to participate in sulfate reduction. This significantly improves the efficiency of extracellular electron acquisition and the sulfate reduction rate of SRBs.

[0044] ② Biological protective barrier: The FeS NPs layer covering the surface of SRB cells forms a physical barrier, which effectively isolates or reduces the direct toxic effects of high concentrations of heavy metal ions in wastewater on SRB cells, and improves the survival rate and activity stability of SRB in harsh wastewater environments.

[0045] ③ Synergistic removal of heavy metals: The Bio-FeS@SRB hybrid combines the biological activity of SRB with the strong chemical activity of FeS NPs. On the one hand, FeS NPs are effective against various heavy metal ions (such as...) (e.g., Cr(VI)) possesses extremely strong adsorption capacity and high reactivity, and can form more insoluble metal sulfide precipitates or fix them through surface complexation. On the other hand, some high-valence heavy metals (such as Cr(VI)) can be directly reduced to low-valence states (such as Cr(III)) by SRB or FeS, reducing toxicity and facilitating precipitation removal.

[0046] The formation of Bio-FeS@SRB is an in-situ, self-assembly process. Its unique structure enables deep coupling and synergistic effect between bioreduction (SRB) and chemical precipitation (FeS NPs), which not only significantly improves the simultaneous removal efficiency of sulfate and various heavy metals, but also enhances the system's tolerance to heavy metal toxicity.

[0047] The present invention will be further described below with reference to specific embodiments.

[0048] Example 1: This example proposes a method for treating mine wastewater using a weakly electrically driven in-situ self-assembled Bio-FeS@SRB system, comprising the following steps: (1) Construct a weakly driven electrolysis system; The main structure of the constructed electrolysis system is made of plexiglass. Both the cathode and anode chambers are cubic in shape, with a chamber volume of 125 mL (5 cm × 5 cm × 5 cm). The exchange membrane is a proton exchange membrane (5 cm × 5 cm). The fixed resistor is 10 Ω, and the DC power supply is an external voltage of 0.8 V applied between the cathode and anode.

[0049] Both the anode and cathode electrodes are made of carbon fiber brushes (Φ 3 cm × 5 cm), which are formed by uniformly winding carbon fiber filaments onto a spiral titanium wire (Φ 1 mm) and mechanically twisting them together to ensure structural stability. Before use, the carbon fiber brushes are soaked in acetone solution for more than 12 hours to remove organic contaminants and then rinsed with deionized water. Subsequently, they are calcined in a muffle furnace at 450°C for 20 minutes to enhance hydrophilicity and microbial compatibility.

[0050] The data acquisition device records the voltage across the fixed resistor in real time and calculates the current value using Ohm's law.

[0051] The reference electrode is an Ag / AgCl electrode, with its tip positioned ≤2 cm from the electrode surface to facilitate monitoring of the electrode potential.

[0052] (2) In-situ self-assembly of Bio-FeS@SRB hybrids at the cathode of a weakly driven electrolysis system; First, the SRB bacterial culture was acclimatized and enriched. Anaerobic sludge from the digester of the Chengyang Wastewater Treatment Plant (MLSS = 20 g / L) was used as the bacterial source. Modified Postgate's C medium (containing 4.5 g Na₂SO₄, 1.0 g NH₄Cl, 0.6 g KH₂PO₄, 0.06 g CaCl₂·7H₂O, 0.06 g MgSO₄·7H₂O, 6.0 g C₃H₅O₃Na, 1.0 g Yeastextract, 0.004 g FeSO₄·7H₂O, and 0.3 g sodium citrate per liter, adjusted to pH = 7.2 ± 0.1) was used for the subculturing and enrichment of the SRB bacterial community. Take 90 mL of culture medium into an anaerobic bottle, sterilize at 121℃ for 20 min, purge with nitrogen for 20 min, inoculate 10 mL of anaerobic sludge in a sterile operating table, and culture in a constant temperature shaker. Use 5 days as a cycle (end time of logarithmic phase of the growth curve), and inoculate in the same way for two consecutive months to obtain a highly active SRB mixed bacterial community with a sulfate removal rate of over 70%.

[0053] Next, inoculation is performed, specifically, the in-situ self-assembly of Bio-FeS@SRB hybrids at the cathode. The anolyte for the electrolysis system consists of actual domestic sewage (raw sewage from Chengyang Sewage Treatment Co., Ltd. after sludge removal) (COD = 380 ± 30 mg / L, 40% volume ratio (40% sewage volume in total influent, the remaining 60% is artificially prepared water)) and artificially prepared water (50 mmol / L phosphate buffer solution, 1.0 g / L sodium acetate). The catholyte is simulated acidic mine wastewater and acclimated SRB bacterial solution (OD... 600 ≈0.6, volume ratio is 10%).

[0054] Due to differences in mineral types, hydrology, and climate, the water quality characteristics of AMD vary greatly in terms of pollutant composition, concentration, and acidity. Based on the characteristics of real AMD documented in numerous literatures, simulated acidic mine wastewater was prepared in the laboratory. The chemical composition of the simulated acidic mine wastewater was: 1400 mg / L FeCl2·4H2O, 1000 mg / L Na2SO4. 2- 140 mg / L LOD, 120 mg / L NH4 + -N, pH= 6.

[0055] The concentrations of the above-mentioned indicators in the domestic sewage are: 380±30 mg / L COD, 45±5 mg / L TN, 35 mg / L NH3. 4 + -N, 20mg / L NO3 - -N, 12 mg / L TP, pH=7.5.

[0056] A 0.8 V voltage is applied between the anode and cathode using a DC power supply, and the current response changes are recorded by a data acquisition unit across a fixed resistor. The solution is replaced every 72 hours. When three consecutive batches of the catholyte... When the removal rate is stable at over 70% and the fluctuation of the removal rate between adjacent batches is less than 5%, and the current-time curve shows a stable and repeatable upward and plateau characteristics, the inoculation is considered complete.

[0057] (3) Treat mine wastewater; During normal operation, only artificially prepared water is introduced into the anolyte, and only the mine wastewater to be treated (with an additional 10-50 mg / L Cr(VI) added to the previous components) is introduced into the catholyte, while other conditions remain consistent. Biofilm on the cathode carbon brush is collected and characterized by SEM-EDS after pretreatment (e.g., Figure 2 As shown), from Figure 2 It can be seen that the surface of SRB cells is coated with nanoparticles, and mapping shows that Fe and S elements are co-localized. Figure 3 XRD analysis also confirmed the presence of FeS characteristic peaks. The enhancing effect of nano-FeS on electron transport was also confirmed by the output current curve, such as... Figure 4 As shown.

[0058] Figure 5a This represents the sulfate removal rate of the electrolysis system under different concentrations of Cr(VI). In the absence of... Under the specified conditions (SRB group), the sulfate removal rate decreased sharply with increasing Cr(VI) concentration, from 70.6 ± 2.3% to near 0%, indicating that Cr(VI) has a strong inhibitory effect on the SRB bacterial community. In contrast, the addition of... The Bio-FeS@SRB group exhibited higher removal rates at all Cr(VI) concentrations, maintaining a removal rate of approximately 27% even at high concentrations (50 mg / L) of Cr(VI), demonstrating that the generated nano-FeS effectively alleviated Cr(VI) toxicity and significantly improved the sulfate reduction capacity of the system.

[0059] Bio-FeS@SRB hybrid significantly promoted the removal rate of Cr(VI) from 10 to 50 mg / L, especially at an initial Cr(VI) concentration of 50 mg / L. SRB's Cr(VI) removal rate was only 2.7 ± 0.8%, while Bio-FeS@SRB's Cr(VI) removal rate increased to 41.4 ± 0.9%. Figure 5b ).

[0060] Example 2: This embodiment proposes a method for treating mine wastewater by in-situ self-assembly of Bio-FeS@SRB driven by weak current. It is basically the same as Embodiment 1, except that a potentiostat is used to provide a potential of -0.7 V to the cathode, a carbon felt (4 cm × 4 cm) is used as the anode electrode, and a graphite plate (4 cm × 4 cm) is used as the cathode electrode.

[0061] Example 3: This embodiment proposes a method for treating mine wastewater by in-situ self-assembly of Bio-FeS@SRB driven by weak current. It is basically the same as Embodiment 1, except that the anolyte is actual domestic sewage during normal operation.

[0062] Example 4: This embodiment presents a method for treating mine wastewater using a weakly electrically driven in-situ self-assembled Bio-FeS@SRB, which is basically the same as Embodiment 1, except that during normal operation, the catholyte simulates the chemical composition of acidic mine wastewater as follows: 1400 mg / L FeCl2·4H2O, 1000 mg / L Na2SO4. 2- 10mg / L Cu 2+ 25mg / L Zn 2+ 10 mg / L Cd 2+ 10 mg / L Pb 2+ 140 mg / L COD, 120 mg / L NH4 + -N, pH= 6.

[0063] Figure 6 This represents the removal efficiency of heavy metals Cu(II), Zn(II), Pb(II), and Cd(II) in the method of this invention. After in-situ self-assembly to form Bio-FeS@SRB, the removal rate of Cu(II), Zn(II), Pb(II), and Cd(II) by the electrolysis system increased from 60.7-76.0% to 90.8-96.7%, confirming the enhancing effect of nano-FeS self-assembly on the removal of multiple heavy metal ions.

[0064] Example 5: This embodiment proposes a method for treating mine wastewater by in-situ self-assembly of Bio-FeS@SRB driven by weak current. It is basically the same as Embodiment 1, except that different voltages (0.6 V, 0.8 V, 1.0 V) are applied between the anode and cathode using a DC power supply to examine the efficiency of the electrolysis system under different voltage intensities.

[0065] Figure 7 The output current of the electrolysis system varies under different voltage intensities. As the applied voltage increases from 0.6 V to 1.0 V, the output current of the electrolysis system increases significantly.

[0066] Figure 8 These are scanning electron microscope (SEM) images of Bio-FeS@SRB hybrids generated at the cathode of the electrolysis system under different voltage intensities. Statistical analysis of the FeS nanoparticle size on the SRB surface revealed that the average particle size of the FeS nanoparticles generated at 0.8 V was the smallest, at 24.46 nm, while the average particle sizes of the FeS nanoparticles generated at 0.6 V and 1.0 V were 38.13 nm and 85.48 nm, respectively.

[0067] Figure 9 The figure shows the removal efficiency of the electrolysis system for Cr(VI) under different voltage intensities. As can be seen from the figure, increasing the external voltage significantly improves the system's removal efficiency and tolerance to Cr(VI). At 0.6V, the removal rate decreases sharply with increasing Cr(VI) concentration (from 96.7% to 53.1%); however, when the voltage is increased to 0.8V and 1.0V, the system maintains a high removal rate at all concentrations (especially reaching 74.2% and 70.1% at 50 mg / L, respectively), indicating that the increased voltage effectively enhances electron supply and reduction capabilities, significantly improving the system's stability against Cr(VI) toxicity.

[0068] comprehensive Figure 8 and Figure 9 The results show that 0.8 V was chosen as the optimal voltage because: the nano-FeS particles generated under 0.8 V voltage conditions have the smallest particle size (24.46 nm), and the larger specific surface area makes them more reactive; at the same time, the electrolysis system still maintains a high efficiency and stable removal rate for high concentrations of Cr(VI) (74.2% at 50 mg / L) under this voltage, achieving the best balance between reactivity and treatment efficiency.

[0069] Example 6: This embodiment presents a method for treating mine wastewater using a weakly electrically driven in-situ self-assembled Bio-FeS@SRB system. This method is essentially the same as in Embodiment 1, except that the simulated acidic mine wastewater has a chemical composition of 600 mg / L Fe. 3+ 1500mg / LSO4 2- , 10-50mg / L Cr(VI), 140mg / L COD, 120mg / L NH4 + -N, pH= 6.

[0070] Figure 10 The removal rate of Cr(VI) by SRB without external voltage application is shown. Fe is added to SRB without external voltage application. 3+ The limited improvement in Cr(VI) removal rate indicates that... It is difficult to utilize itself effectively.

[0071] Figure 11 The figure shows the removal efficiency of Cr(VI) by the electrolytic system when an external voltage of 0.8 V is applied. After applying a voltage of 0.8 V, the removal efficiency of the system shows a significant increase, demonstrating that the applied voltage will [result in a significant increase in Cr(VI) removal efficiency]. At the cathode, it is reduced to This leads to the generation of SRB. In-situ generation of highly active nano-FeS; this electrochemically driven FeS generation process greatly enhances electron transfer and Cr(VI) reduction capabilities, which is key to performance improvement. The parts not mentioned above can be achieved by adopting or drawing upon existing technologies.

[0072] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for treating mine wastewater using in-situ self-assembly of Bio-FeS@SRB driven by weak current, characterized in that... Includes the following steps: (1) Construct a weakly driven electrolysis system; The weak current driven electrolysis system includes a reaction cell, inside which an exchange membrane is installed, dividing the reaction cell into an anode chamber and a cathode chamber. An anode is installed in the anode chamber, and a cathode is installed in the cathode chamber. A reference electrode is also installed in both the anode and cathode chambers. Both the anode and cathode are connected to a DC power supply through wires to form a current loop. A resistor is connected in series with a wire, and a data acquisition device is connected across the resistor to record the voltage across the resistor in real time. (2) In-situ self-assembly of Bio-FeS@SRB hybrids at the cathode of a weakly driven electrolysis system; Organic wastewater and artificially prepared water are added to the anode chamber of the weakly driven electrolysis system to form an anolyte. Simulated mine wastewater and SRB bacterial solution are added to the cathode chamber of the weak electric drive electrolysis system to form catholy solution; A voltage of 0.4~1.0 V is applied between the anode and cathode using a DC power supply; During the application of voltage, the SRB bacterial solution in the cathode chamber will simulate the effects of mine wastewater. Reduction , It reacts with the iron source in simulated mine wastewater to generate ferrous sulfide nanoparticles in situ. These ferrous sulfide nanoparticles spontaneously coat the surface of SRB cells to form Bio-FeS@SRB hybrids. (3) Treat mine wastewater; Artificial water is added to the anode chamber of the weak current driven electrolysis system, and the mine wastewater to be treated is added to the cathode chamber. A voltage of 0.4~1.0 V is applied between the anode and cathode through a DC power supply. During the treatment process, sulfates and heavy metals in the mine wastewater to be treated can be removed simultaneously.

2. The method for treating mine wastewater using weakly electrically driven in-situ self-assembly of Bio-FeS@SRB according to claim 1, characterized in that, In step (1): both the anode and cathode are made of carbon fiber brushes; before use, the carbon fiber brushes are soaked in acetone solution for more than 12 hours, then rinsed with deionized water, and then calcined in a muffle furnace at 450~500℃ for 20~30 minutes. The reference electrode is an Ag / AgCl electrode, with its lower part placed below the liquid surface in the anode or cathode chamber, and the distance between the reference electrode and the anode or cathode is ≤2 cm.

3. The method for treating mine wastewater using weakly electrically driven in-situ self-assembly of Bio-FeS@SRB according to claim 1, characterized in that, In step (2): the anolyte contains anodic bacteria, which are derived from organic wastewater and / or sludge; the organic wastewater is domestic sewage, industrial wastewater and / or aquaculture wastewater, with a COD content of 200~8000 mg / L and a pH of 6.5~8.5; the sludge is selected from the anaerobic digester of a municipal sewage treatment plant, with a mixed liquor suspended solids concentration of 20000~40000 mg / L and a pH of 7.0~7.

2.

4. The method for treating mine wastewater using weakly electrically driven in-situ self-assembly of Bio-FeS@SRB according to claim 1, characterized in that, In step (2): the concentration of sodium acetate in the artificially prepared water is 1.0 g / L, the concentration of phosphate buffer solution is 50 mmol / L, and the pH value is 7.0-7.

5.

5. The method for treating mine wastewater using weakly electrically driven in-situ self-assembly of Bio-FeS@SRB according to claim 1, characterized in that, In step (2): the SRB bacterial solution uses anaerobic sludge from the digester of a sewage treatment plant as the bacterial source, and the SRB bacterial community is passaged and enriched using modified Postgate's C medium.

6. The method for treating mine wastewater using weakly electrically driven in-situ self-assembly of Bio-FeS@SRB according to claim 1, characterized in that, In step (2): the simulated mine wastewater contains SO4. 2– 600~5000 mg / L, Fe 2+ 200~3000mg / L, pH value 6.0~7.

5.

7. The method for treating mine wastewater using weakly electrically driven in-situ self-assembly of Bio-FeS@SRB according to claim 1, characterized in that, In step (2): the anolyte and catholyte are replaced every 24-72 hours; the current response changes are recorded using a data acquisition device. When the current response changes within three consecutive batches... When the removal rate is stable at over 70% and the removal rate fluctuation between adjacent batches is less than 5%, and the current-time curve shows a stable and repeatable upward and plateau characteristics, it is considered that the inoculation is complete, and the in-situ self-assembly of Bio-FeS@SRB hybrid is completed at the cathode of the weakly driven electrolysis system.

8. The method for treating mine wastewater using weakly electrically driven in-situ self-assembly of Bio-FeS@SRB according to claim 1, characterized in that, In step (3): the concentration of sodium acetate in the artificially prepared water is 1.0 g / L, the concentration of phosphate buffer solution is 50 mmol / L, and the pH value is 7.0-7.5; Domestic sewage to be treated is also added to the anode chamber, so that domestic sewage can be treated simultaneously during the mining wastewater treatment process.

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