Method for fixing and magnetically separating arsenic in water by biomineralization

Abstract

The application discloses a method for fixing and magnetically separating arsenic in water by using biological mineralization, and comprises the following steps: S1, liquid medium preparation: dissolving 60% (volume) sodium lactate solution, sodium nitrate, potassium dihydrogen phosphate, magnesium sulfate heptahydrate and yeast extract in deionized water according to proportions, adjusting the pH of the medium solution to 6.9-7.0, and performing high-pressure sterilization after being divided into small portions; S2, inoculating bacteria liquid into the sterilized medium to perform amplification culture; S3, preparing a standard arsenic solution; S4, preparing iron citrate and ferrous chloride solutions; S5, MSR-1 biological control mineralization synthesis of magnetosomes; S6, MSR-1 induced bivalent iron precipitation for arsenic removal; and S7, magnetic separation of bacteria-iron-arsenic mixture. The method realizes the fixation and separation of arsenic in water, retains the advantages of low cost and environmental friendliness of the biological mineralization for repairing contaminated water, and overcomes the disadvantages of low repair efficiency and potential pollution caused by the inability to recycle.

Description

Technical Field

[0001] This invention belongs to the field of microbial remediation technology for As-contaminated water, and in particular relates to a method for using microbial mineralization fixation and magnetic separation of arsenic in water. Background Technology

[0002] As and its inorganic compounds have been classified as Group 1 carcinogens by the World Health Organization. In nature, as primarily exists in two mineral forms: arsenic oxides and ferric arsenate. Mining, groundwater extraction, and chemical smelting processes expose asphalt, originally contained in the solid phase of soil or ore, to the surface environment. Trivalent asphalt is easily oxidized to pentavalent asphalt by oxygen in the air. Under the scouring, erosion, and dissolution effects of rainwater, surface water, and groundwater, asphalt in the solid phase is mostly converted to AsO4. 3- As is dissolved in the aqueous phase. As has high mobility in water and poses a direct or indirect threat to human health through well water use, river water irrigation, and other means. Therefore, effective remediation of as polluted water is crucial to safeguarding public health and promoting social development.

[0003] Currently, common water remediation technologies for arsenic (As) include adsorption based on single or composite materials, chemical precipitation, ion exchange, flocculation, electrodialysis, and reverse osmosis. Based on the characteristics of As's occurrence in water and the adsorption properties of its compounds, amorphous iron minerals with abundant As complexation sites, formed by bacterial bio-induced mineralization (BOCs) and other bacteria, have become preferred materials for As removal via adsorption. This bioremediation technology can be used to remediate As-contaminated water in arid, iron-poor regions. However, As fixed by bacterial-iron mineral materials remains an unstable pollutant; bacterial metabolic activities or iron mineral transformation can lead to secondary As release. Therefore, arsenic removal should not only focus on removing dissolved arsenic but also on separating solid arsenic from the aquatic environment. In other words, the development of microbial bio-induced mineralization and As fixation technologies should be coupled with As separation and recovery technologies. Magnetotactic bacteria, under microaerobic conditions, form magnetosomes through bio-controlled mineralization, giving them magnetotactic properties. Methods to achieve As fixation through bio-induced mineralization and magnetic recovery of the bacterial-iron-arsenic complex while retaining this property require further investigation. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for fixing arsenic in water using microbial mineralization and magnetic separation. This method has high fixation efficiency and can achieve arsenic recovery.

[0005] Therefore, the present invention adopts the following technical solution:

[0006] A method for removing and magnetically separating arsenic from water using biomineralization includes the following steps:

[0007] S1, Preparation of liquid culture medium:

[0008] Dissolve 60% (volume) sodium lactate solution, sodium nitrate, potassium dihydrogen phosphate, magnesium sulfate heptahydrate, and yeast extract in deionized water at the following ratios to achieve concentrations of 2.2–3 g / L, 0.3–0.4 g / L, 0.1–0.12 g / L, 0.15–0.2 g / L, and 0.1–0.12 g / L, respectively. Adjust the pH of the culture medium solution to 6.9–7.0. Dispense 50 ml of culture medium into each 100 ml serum bottle, then seal the serum bottles and autoclave them. After sterilization, cool the serum bottles to room temperature to obtain multiple sterilized culture media.

[0009] S2, bacterial culture:

[0010] In a sterile operating table, *Griffiths filamentosa* bacterial suspension was inoculated into the partially sterilized culture medium obtained in S1. After sealing the serum bottle, it was placed in a constant temperature shaker for amplification culture. The obtained OD... 565 The bacterial suspension is 0.9–1.1, wherein the volume of *Griffithswald* bacterial suspension inoculated in each serum bottle is 5–10% of the volume of the culture medium in the bottle;

[0011] S3, Prepare a standard arsenic solution:

[0012] Prepare a 1 g / L standard As(V) solution using trisodium arsenate and deionized water;

[0013] S4, Prepare a solution of ferric citrate and ferrous chloride:

[0014] Prepare a 200 mg / L ferric citrate solution using ferric citrate and deionized water; boil the deionized water to obtain deoxygenated water, blow it with nitrogen until the temperature of the deoxygenated water drops to room temperature, and then store it in an anaerobic glove box; dissolve ferrous chloride in the deoxygenated water in the anaerobic glove box to prepare a 1 g / L ferrous chloride solution.

[0015] S5, MSR-1 biocontrolled mineralization synthesis of magnetosomes:

[0016] The ferric citrate solution and standard As solution were filtered using a sterile filter to remove bacteria. The filtered ferric citrate solution and standard As solution were added to the sterile culture medium obtained in S1, so that the concentration of ferric citrate solution in the sterile culture medium was 5-50 mg / L and the concentration of As(V) was 0.5-20 mg / L. Then, the bacterial culture obtained from the expansion culture in step S2 was inoculated at a volume of 5-10% of the culture medium. The sterile culture medium after inoculation was placed in a constant temperature shaker and cultured for 18-22 h to obtain the bacterial culture that synthesized magnetosomes and perform simple verification.

[0017] S6.MSR-1 induces ferrous iron precipitation for arsenic removal;

[0018] The ferrous chloride solution prepared in S4 was filtered using a sterile filter. The filtered ferrous chloride solution was then injected into the bacterial solution obtained in S5 in a sterile operating table to make the initial concentration of ferrous iron in the bacterial solution 200-600 mg / L. The solution was then placed in a constant temperature shaker for 6-12 hours to react.

[0019] S7. Magnetic separation bacteria-iron-arsenic mixture:

[0020] A strong magnet was attached to the wall of the serum bottle obtained in S6 for 4-6 hours. The solid mixture that had accumulated at the magnetic pole on the bottle wall was scraped off with a small spoon. The magnetic attraction and scraping operation was repeated until no obvious solid mixture was attached to the bottle wall. The collected mixtures were combined, and the total arsenic fixed by bacterial iron precipitate was finally obtained outside the water.

[0021] In S1 above, the serum bottle is sealed with a gas-exchangeable sealing film and placed in an autoclave for sterilization at 120-125°C for 20-25 minutes. After sterilization, the serum bottle is placed in a sterile operating table to cool to room temperature.

[0022] In S1, HCl and NaOH were used to adjust the pH of the culture medium solution.

[0023] In S2 and S5, the temperature of the constant temperature oscillator is 30℃ and the vibration speed is 100rpm.

[0024] The preparation method of standard As(V) solution in S3 is as follows: accurately weigh 2.7748g of trisodium arsenate, add it to 500ml of deionized water and sonicate until completely dissolved, transfer the solution to a 1L volumetric flask, and add deionized water to make up to 1000mL.

[0025] The simple verification method described in S5 is to judge by whether the color of the bacteria turns grayish-black or by observing whether the bacteria rotate with the magnetic field on the magnetic stirrer.

[0026] The principle of this invention for removing arsenic (As) pollutants from water through magnetotactic bacterial biomineralization is as follows: Magnetorheic bacteria from Griffithwald (MSR-1) first absorb iron ions from ferric citrate under microaerobic conditions. Subsequently, the cell membrane invaginates to form a magnetosome membrane. After the iron ions enter the magnetosome membrane, a protein-regulated redox reaction occurs, ultimately forming biofilm-coated magnetite nanoparticles, also known as magnetosomes. With the continued addition of ferrous chloride, the negatively charged MSR-1 cells attract and adsorb / complex with a large number of positively charged ferrous ions. Under the accelerated oxidation effect of the bacterial extracellular polymeric functional groups, a large number of ferrous ions are deposited on the bacterial surface as a template to form amorphous iron minerals. During mineral formation, co-precipitation and adsorption / complexation reactions of As occur simultaneously, thereby fixing dissolved arsenic in the water. Utilizing the magnetotactic properties imparted to the bacteria by the magnetosomes, under the action of an external magnetic field, the MSR-1 cells, loaded with iron-arsenic coprecipitates, move directionally in the water, achieving the separation of arsenic pollutants.

[0027] This invention addresses the problems of low efficiency in biomineralization for As (As) removal and the inability to effectively separate arsenic in existing microbial mineralization remediation technologies for As contaminated water. It proposes a dual biomineralization remediation method using magnetotactic bacteria, suitable for efficient As fixation and magnetic separation in water. This method combines two modes of bio-induced mineralization and bio-controlled mineralization by the same microorganism to achieve As fixation and magnetic separation in water sequentially. The specific roles of the two biomineralization methods are as follows: Magnetotactic bacteria MSR-1 form amorphous iron precipitates through bio-induced mineralization, achieving efficient As fixation in water; Magnetotactic bacteria MSR-1 synthesize magnetosomes through bio-controlled mineralization, giving them magnetotactic properties, thereby separating the magnetotactic bacteria loaded with iron-arsenic minerals from the water under a magnetic field.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. This invention uses magnetotactic bacteria to induce ferrous iron to complete bio-induced mineralization. The ability of magnetotactic bacteria to accommodate or absorb iron is 100-1000 times that of ordinary bacteria. The high affinity of these bacteria for iron ions enables them to rapidly induce ferrous iron to form a large amount of mineralization using the cell surface as a deposition template, thereby improving the fixation efficiency of As in water.

[0030] 2. The magnetotactic bacteria selected in this invention have the characteristic of synthesizing magnetosomes intracellularly, which gives these bacteria a unique and stable magnetotactic property. This enables the magnetic separation of As fixed by biomineralization, preventing these As from remaining in the water as an unstable secondary pollution source. The simple magnetic recovery eliminates the cost of monitoring pollutant concentrations in the later stages.

[0031] 3. The bacterial agents and pharmaceuticals used in this invention are inexpensive, and the remediation process is simple and quick. It leverages the advantages of bioremediation, such as sustainability and environmental friendliness, and overcomes the shortcomings of bioremediation, such as long processing time, low efficiency, and difficulty in separating pollutants from water.

[0032] 4. This invention has a wide range of applications. The amorphous iron minerals formed by the bio-induced mineralization of magnetotactic bacteria can be used for the remediation of polluted water environments containing anionic pollutants, siderophilic organic pollutants, or both. As facultative anaerobic bacteria, magnetotactic bacteria can be applied to the remediation of water pollution under a wide range of dissolved oxygen concentrations. Attached Figure Description

[0033] Figure 1 OD values ​​of MSR-1 bacterial cultures under different As concentrations 565 Value diagram;

[0034] Figure 2 This is a schematic diagram illustrating the effect of reaction time on the efficiency of bio-induced ferrous iron precipitation in removing As(V).

[0035] Figure 3 This is a schematic diagram illustrating the effect of initial As(V) concentration on the efficiency of As(V) removal by biologically induced ferrous iron precipitation.

[0036] Figure 4 This is a schematic diagram illustrating the effect of initial ferrous iron concentration on the efficiency of biologically induced ferrous iron precipitation in removing As(V).

[0037] Figure 5 This is a schematic diagram showing the effect of the initial ferric citrate concentration on the efficiency of magnetic separation of As(V) in water. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining this invention and are not intended to limit this invention.

[0039] The method of this invention involves inoculating MSR-1 bacteria into a liquid culture medium containing sodium lactate, sodium nitrate, potassium dihydrogen phosphate, magnesium sulfate heptahydrate, and yeast extract for activation and expansion culture. The expanded bacteria are then inoculated into a liquid culture medium containing trisodium arsenate and ferric citrate. After the bacteria complete biocontrolled mineralization, i.e., magnetosome synthesis, ferrous chloride is added to induce bio-induced mineralization. As in the water is fixed by inducing amorphous iron minerals to precipitate onto the bacterial surface. Finally, the magnetotaxis of MSR-1 separates it from the water along with the surface iron-arsenic precipitate.

[0040] The *Griffithswald* strain used in the following examples (MSR-1) was purchased from the German Microbial Culture Collection (DSMZ), accession number: DSM 6361.

[0041] Example 1

[0042] The following steps were included in testing the tolerance of MSR-1 to As under different As concentrations:

[0043] S1. Dissolve 60% sodium lactate solution, sodium nitrate, potassium dihydrogen phosphate, magnesium sulfate heptahydrate, and yeast extract in deionized water to achieve concentrations of 2.6 g / L (sodium lactate solution concentration in deionized water), 0.34 g / L, 0.1 g / L, 0.15 g / L, and 0.1 g / L, respectively. Adjust the pH of the culture medium solution to 7.0. Dispense 50 ml of culture medium into each 100 ml serum bottle. Seal the serum bottles with a gas-exchange sealing film and sterilize them in an autoclave at 120°C for 20 min. After sterilization, cool the culture medium to room temperature in a sterile operating table to obtain multiple sterilized culture media.

[0044] S2. In a sterile operating table, take a portion of sterile culture medium and inoculate it with 5-10% of the volume of MSR-1 bacterial suspension. Seal the serum bottle with a rubber stopper and aluminum cap, and place the bottle in a constant temperature shaker (30℃, 100rpm) for expansion culture to obtain OD. 565 For bacterial culture.

[0045] S3. Accurately weigh 2.7748g of trisodium arsenate, add it to 500ml of deionized water and sonicate until completely dissolved. Transfer the solution to a 1L volumetric flask, add deionized water to make up to 1000mL, and obtain a 1g / L standard As(V) solution.

[0046] S4. Filter the standard As solution using a sterile filter, and gradually dilute the standard As(V) solution with sterile water in a sterile operating table. Add different concentrations of As(V) solution to the sterile culture medium obtained in S1, so that the concentration of As(V) in the culture medium is 0, 0.5, 5, 20, 50, and 200 mg / L, respectively. Inoculate the bacterial suspension obtained in S2 with an inoculation amount of 5-10% of the culture medium volume and incubate in a constant temperature shaker (30℃, 100 rpm).

[0047] S5. Samples of the bacterial culture from step S4 are taken at intervals between 0 and 24 hours, and the OD of the bacterial culture is measured using a spectrophotometer. 565 value.

[0048] Figure 1 OD values ​​of bacterial cultures at different As(V) concentrations 565 The values ​​changed. It can be seen that the dissolved As concentration in the range of 0-50 mg / L has no significant effect on bacterial growth, and MSR-1 has good arsenic tolerance.

[0049] Example 2

[0050] The effect of different reaction times on the removal of arsenic by bio-induced ferrous iron precipitation was tested, including the following steps:

[0051] S1 to S3 are the same as in Example 1.

[0052] S4. Weigh 200 mg of ferric citrate and dissolve it in 1 L of deionized water to obtain a 200 mg / L ferric citrate solution. Boil the deionized water and purge it with nitrogen for 1 hour. After the oxygen-free water temperature drops to room temperature, store it in an anaerobic glove box. Weigh 2.2695 g of ferrous chloride and dissolve it in 1 L of deoxygenated water in the anaerobic glove box to obtain a 1 g / L ferrous chloride solution.

[0053] S5. Filter the ferric citrate and standard As(V) solution using a sterile filter. Add the ferric citrate solution and As(V) solution to the sterile culture medium obtained in S1, so that the concentration of ferric citrate solution in the culture medium is 15 mg / L and the concentration of As(V) is 50 mg / L. Inoculate the OD obtained from the expansion culture in step S2. 565 The bacterial culture was prepared at a concentration of 1.0 and cultured in a constant temperature shaker (30℃, 100rpm). After 18 hours, the dissolved oxygen concentration in the solution reached the micro-oxygen conditions suitable for the synthesis of magnetosomes.

[0054] S6. In a sterile operating table, use a syringe to draw 1-2 ml of bacterial solution that has reached microaerobic conditions in S5. Determine whether MSR-1 has successfully synthesized magnetosomes by observing changes in bacterial color or whether the bacteria respond to changes in the magnetic field of the magnetic stirrer.

[0055] Specifically, when the bacterial cell color changes from its original white or light pink to grayish-black, the overall water color darkens, indicating that *Griffithswald* has synthesized magnetosomes intracellularly. Alternatively, placing the serum bottle on an open magnetic stirrer and observing the bacterial colony rotating within the bottle confirms successful magnetosome synthesis.

[0056] S7. Filter the ferrous chloride solution using a sterile filter. Inject the ferrous chloride solution into the bacterial culture after confirming the synthesis of magnetosomes in step S5 under a sterile operating table. The initial ferrous iron concentration is 200 mg / L. Take samples at intervals within 15 h. After filtering with a 0.22 μM filter membrane, test the As(V) concentration by ICP-MS.

[0057] Figure 2 This diagram illustrates the effect of different reaction times on the efficiency of As(V) removal by bio-induced ferrous precipitation. It shows that the As(V) removal rate reaches its highest level at 12 hours after the addition of ferrous chloride, indicating that the MSR-1 bio-induced ferrous precipitation reaction can achieve efficient As(V) fixation in water within 12 hours.

[0058] Example 3

[0059] The effect of different initial As(V) concentrations on the removal of As(V) by bio-induced ferrous iron precipitation was tested, including the following steps:

[0060] S1 to S4 are the same as in Example 2.

[0061] S5. Filter ferric citrate and standard As(V) solution using a sterile filter. Add ferric citrate solution and As(V) solutions of different concentrations to the sterile culture medium obtained in S1, so that the concentration of ferric citrate solution in the culture medium is 15 mg / L, and the concentration of As(V) is 0, 0.5, 5, 20, 50, and 200 mg / L. Inoculate the OD obtained from the expansion culture in step S2. 565 The bacterial culture was prepared at a concentration of 1.0 and cultured in a constant temperature shaker (30℃, 100rpm). After 18 hours, the dissolved oxygen concentration in the solution reached microaerobic conditions, and magnetosomes were synthesized.

[0062] S6. Using a syringe, extract 1-2 ml of bacterial culture from step S5 after 18-22 hours of incubation in a sterile operating table. Determine whether MSR-1 has successfully synthesized magnetosomes by observing changes in bacterial color and whether the bacteria respond to changes in the magnetic field of the magnetic stirrer.

[0063] S7. Filter the ferrous chloride solution using a sterile filter. Inject the ferrous chloride solution into the bacterial culture after confirming the synthesis of magnetosomes in step S5 under a sterile operating table. The initial ferrous iron concentration is 200 mg / L. Take a sample at 12 h, filter it using a 0.22 μM filter membrane, and test the As(V) concentration by ICP-MS.

[0064] Figure 3 This diagram illustrates the effect of initial As(V) concentration on the efficiency of As(V) removal by bio-induced ferrous iron precipitation. It shows that when the initial ferrous iron concentration is 200 mg / L, the As(V) removal rate is above 90% for initial As concentrations in the range of 0.5-20 mg / L, indicating a good removal effect.

[0065] Example 4

[0066] The effect of different initial ferrous chloride concentrations on the removal of As(V) by bio-induced ferrous precipitation was tested, including the following steps:

[0067] S1 to S4 are the same as in Example 2.

[0068] S5. Filter ferric citrate and standard As(V) solution using a sterile filter. Add ferric citrate solution and As(V) solution to the sterilized culture medium obtained in S1, so that the concentration of ferric citrate solution in the culture medium is 15 mg / L and the concentration of As(V) is 20 mg / L. Inoculate the OD obtained from the expansion culture in step S2. 565 The bacterial culture was prepared at a concentration of 1.0 and cultured in a constant temperature shaker (30℃, 100rpm). After 18 hours, the dissolved oxygen concentration in the solution reached the micro-oxygen conditions suitable for the synthesis of magnetosomes.

[0069] S6. Using a syringe, draw 1-2 ml of bacterial solution that has reached microaerobic conditions in step S5 in a sterile operating table. Determine whether MSR-1 has successfully synthesized magnetosomes by observing changes in bacterial color and whether the bacteria respond to changes in the magnetic field of the magnetic stirrer.

[0070] S7. Filter the ferrous chloride solution using a sterile filter. Inject different concentrations of ferrous chloride solution into the bacterial culture after confirming the synthesis of magnetosomes in step S5 under a sterile operating table, so that the initial ferrous divalent concentration is 0, 20, 80, 200, 400, and 600 mg / L. Take samples at 12 h after the reaction, filter them using a 0.22 μM filter membrane, and test the As(V) concentration by ICP-MS.

[0071] Figure 4 This diagram illustrates the effect of initial ferrous iron concentration on the efficiency of As(V) removal by bio-induced ferrous iron precipitation. It shows that when the initial ferrous iron concentration is in the range of 200-600 mg / L, the As removal rate can exceed 90%.

[0072] Example 5

[0073] The effect of different initial ferric citrate concentrations on the efficiency of As separation in magnetic water was tested, including the following steps:

[0074] S1 to S4 are the same as in Example 2.

[0075] S5. Filter ferric citrate and standard As(V) solution using a sterile filter. Add ferric citrate solution and As(V) solution to the sterilized culture medium obtained in S1, so that the concentration of ferric citrate solution in the culture medium is 0, 1, 5, 15, 50, 200 mg / L, and the concentration of As(V) is 20 mg / L. Inoculate the OD obtained from the expansion culture in step S2. 565 The bacterial suspension was prepared at a concentration of 0.9–1.1 and cultured in a constant temperature shaker (30°C, 100 rpm). After 18 hours, the dissolved oxygen concentration in the solution reached the micro-oxygen conditions suitable for magnetosome synthesis.

[0076] S6. Using a syringe, draw 1-2 ml of bacterial solution that has reached microaerobic conditions in step S5 in a sterile operating table. Determine whether MSR-1 has successfully synthesized magnetosomes by observing changes in bacterial color and whether the bacteria respond to changes in the magnetic field of the magnetic stirrer.

[0077] S7. Filter the ferrous chloride solution using a sterile filter. Inject the ferrous chloride solution into the bacterial culture grown for 24 hours in step S5 under sterile conditions. The initial iron concentration is 200 mg / L. Continue the reaction for 12 hours. At 36 hours, attach a strong magnet to the wall of the serum bottle for 4 hours. Use a small spoon to scrape the solid mixture that has accumulated at the magnetic pole on the bottle wall. Repeat this process 2-3 times. Combine the collected mixtures and digest the mixture by adding 3 ml of concentrated nitric acid for 12 hours. Dilute and filter the resulting digest and test the As(V) content using ICP-MS. Further calculate the As(V) recovery rate.

[0078] Figure 5 This diagram illustrates the effect of initial ferric citrate concentration on the magnetic separation efficiency of As(V) in water. It shows that the magnetic recovery rate of As(V) can reach 82%-92% when the initial ferric citrate concentration is 5-50 mg / L, and reaches a maximum of 92% when the initial ferric citrate concentration is 15 mg / L.

Claims

1. A method for fixing and magnetically separating arsenic in water using biomineralization, characterized in that, Includes the following steps: S1, Preparation of liquid culture medium: A 60% (v / v) sodium lactate solution, sodium nitrate, potassium dihydrogen phosphate, magnesium sulfate heptahydrate, and yeast extract were dissolved in deionized water at specific ratios to achieve concentrations of 2.2–3 g / L, 0.3–0.4 g / L, 0.1–0.12 g / L, 0.15–0.2 g / L, and 0.1–0.12 g / L, respectively. The pH of the culture medium solution was adjusted to 6.9–7.

0. 50 ml of culture medium was dispensed into each 100 ml serum bottle. The serum bottles were then sealed and autoclaved. After sterilization, the serum bottles were cooled to room temperature to obtain multiple sterilized culture media. S2, bacterial culture: In a sterile operating table, *Griffiths filamentosa* bacterial suspension was inoculated into the partially sterilized culture medium obtained in S1. After sealing the serum bottle, it was placed in a constant temperature shaker for amplification culture. The obtained OD... 565 The bacterial suspension concentration was 0.9–1.1, wherein the volume of *Griffithswald* bacterial suspension inoculated in each serum bottle was 5–10% of the volume of the culture medium in the bottle; S3, Prepare a standard arsenic solution: Prepare a 1 g / L standard As(V) solution using trisodium arsenate and deionized water; S4, Prepare a solution of ferric citrate and ferrous chloride: Prepare a 200 mg / L ferric citrate solution using ferric citrate and deionized water; boil the deionized water to obtain deoxygenated water, blow it with nitrogen until the temperature of the deoxygenated water drops to room temperature, and then store it in an anaerobic glove box; dissolve ferrous chloride in the deoxygenated water in the anaerobic glove box to prepare a 1 g / L ferrous chloride solution. S5, MSR-1 biocontrolled mineralization synthesis magnetosomes: The ferric citrate solution and standard As solution were filtered using a sterile filter to remove bacteria. The filtered ferric citrate solution and standard As solution were added to the sterile culture medium obtained in S1, so that the concentration of ferric citrate solution in the sterile culture medium was 5-50 mg / L and the concentration of As(V) was 0.5-20 mg / L. Then, the bacterial culture obtained from the expansion culture in step S2 was inoculated at a volume of 5-10% of the culture medium. The sterile culture medium after inoculation was placed in a constant temperature shaker and cultured for 18-22 h to obtain the bacterial culture that synthesized magnetosomes and perform simple verification. S6. MSR-1 induces ferrous iron precipitation for arsenic removal; The ferrous chloride solution prepared in S4 was filtered using a sterile filter. The filtered ferrous chloride solution was then injected into the bacterial solution obtained in S5 in a sterile operating table to make the initial concentration of ferrous iron in the bacterial solution 200-600 mg / L. The solution was then placed in a constant temperature shaker for 6-12 hours to react. S7. Magnetic separation bacteria-iron-arsenic mixture: A strong magnet was attached to the wall of the serum bottle obtained in S6 for 4-6 hours. The solid mixture that had accumulated at the magnetic pole on the bottle wall was scraped off with a small spoon. The magnetic attraction and scraping operation was repeated until no obvious solid mixture was attached to the bottle wall. The collected mixtures were combined, and the total arsenic fixed by bacterial iron precipitate was finally obtained outside the water.

2. The method according to claim 1, characterized in that: In step S1, the serum bottle is sealed with a gas-exchangeable sealing film and placed in an autoclave for sterilization at 120–125°C for 20–25 minutes. After sterilization, the serum bottle is placed in a sterile operating table to cool to room temperature.

3. The method according to claim 1, characterized in that: In S1, HCl and NaOH were used to adjust the pH of the culture medium solution.

4. The method according to claim 1, characterized in that: In S2 and S5, the temperature of the constant temperature oscillator is 30℃ and the vibration speed is 100rpm.

5. The method according to claim 1, characterized in that, The preparation method of standard As(V) solution in S3 is as follows: accurately weigh 2.7748g of trisodium arsenate, add it to 500ml of deionized water and sonicate until completely dissolved, transfer the solution to a 1L volumetric flask, and add deionized water to make up to 1000mL.

6. The method according to claim 1, characterized in that, The simple verification method described in S5 is to judge by whether the color of the bacteria turns grayish-black or by observing whether the bacteria rotate with the magnetic field on the magnetic stirrer.

Images