CN113502304A - FeS nano composite material, preparation method and application thereof - Google Patents

Abstract

The invention provides a preparation method of FeS nano composite material. Compared with the prior art, the present invention utilizes dissimilatory metal-reducing bacteria to use organic matter as a metabolic substrate, and uses water-soluble sulfur-containing compounds and ferric salts as electron acceptors after generating electrons, and Fe ²⁺ and S produced by biological reduction. ^2- combined to form FeS nanoparticles, FeS nanoparticles anchored on the cell surface coupled with bacteria to form bacteria-nanomaterial hybrids, a large number of FeS nanoparticles aggregated outside the cell can effectively remove heavy metals, and also relieve heavy metal ion pairing Toxic effect of bacterial cells; the good conductivity caused by nano FeS further enhances the extracellular electron transfer ability of bacteria, and strengthens the extracellular reduction of heavy metals by bacteria and the regeneration of FeS. At the same time, the reaction product of nano FeS and heavy metals is also Re-synthesis of nano-FeS by bacteria provides electron acceptors, which can realize the cyclic regeneration of nano-FeS.

Description

FeS nano composite material, preparation method and application thereof

Technical Field

The invention belongs to the technical field of wastewater treatment, and particularly relates to a FeS nano composite material, and a preparation method and application thereof.

Background

A large amount of wastewater rich in heavy metals is generated in the production and processing processes of various industries such as mining, metallurgy, electroplating, electronic manufacturing and the like, wherein the common heavy metals such as chromium, copper, nickel, zinc, lead and the like have strong biotoxicity and are seriously dangerous for ecological environment safety and human health. At present, the common methods for treating heavy metal wastewater comprise adsorption, flocculation, membrane treatment, ion exchange, chemical precipitation and the like. Although effective, the physical and chemical methods have the defects of high cost, low removal efficiency and the like, and the generated sludge, concentrated solution, toxic gas and the like containing a large amount of heavy metals have secondary environmental pollution risks. In particular, the commonly adopted sulfide precipitation method usually needs to add sodium sulfide or calcium sulfide as a reducing agent and a precipitating agent, so that heavy metal sludge and residual S in effluent water are generated^2-And generation of H₂S gas can also cause corrosion to equipment. In future, if the heavy metal sludge is brought into hazardous waste management, the treatment method is severely limited.

In response to the problems of the conventional sulfide precipitation method, researchers have proposed a new technology of using ferrous sulfide (FeS) nano material instead of sodium sulfide/calcium sulfide in recent years. Since FeS is insoluble in water, S does not exist in effluent^2-Secondary pollution, and can efficiently remove various heavy metals through various mechanisms such as reduction, ion exchange, adsorption and the like. However, FeS nanoparticles tend to agglomerate and are easily oxidized to iron oxides in the presence of air and trace amounts of moisture, thereby reducing their reactivity. Thus, it is often necessary to load the carrier material and to strictly control the storage and transportation conditions, thereby limiting its practical application.

Compared with a physical and chemical method, the biological method has huge potential advantages and development prospects in the aspect of heavy metal wastewater treatment. The biological method mainly utilizes the adsorption and reduction of microorganisms to remove various heavy metals, and has the advantages of low cost, simple operation, small sludge production and environmental friendliness. For example, dissimilatory metal-reducing bacteria can directly reduce various toxic high-valence heavy metal ions such as Cr (VI) and Cu (II) into non-toxic low-valence ions or metal simple substances, and sulfate-reducing bacteria can utilize hydrogen sulfide generated by the metabolism of the sulfate-reducing bacteria to combine with the heavy metal ions to form metal sulfide precipitates, so that the metal sulfide precipitates can be removed from water. However, the heavy metal wastewater has complex components and strong biological toxicity, and the activity of microorganisms is often severely inhibited when the concentration of heavy metal ions is high, so that the treatment efficiency is low, and the practical engineering application of the method is limited.

Disclosure of Invention

In view of the above, the technical problem to be solved by the present invention is to provide a FeS nanocomposite, a preparation method thereof and an application thereof, wherein the FeS nanocomposite can realize efficient removal of heavy metals by coupling chemical and biological processes.

The invention provides a preparation method of a FeS nano composite material, which is characterized by comprising the following steps:

s) under the anaerobic condition, carrying out shake culture on dissimilatory metal reducing bacteria in a culture solution containing water-soluble ferric salt and water-soluble sulfur-containing compounds to obtain the FeS nano composite material.

Preferably, the dissimilatory metal-reducing bacteria are selected from one or more of Shewanella onandra, Thiodermabacter and Aeromonas hydrophila.

Preferably, the water-soluble ferric salt is selected from one or more of ferric chloride, ferric sulfate, ferric ammonium sulfate and ferric citrate; the water-soluble sulfur-containing compound is selected from one or more of thiosulfate, sulfite and sulfide.

Preferably, the step S) is specifically:

dispersing dissimilatory metal reducing bacteria in the culture solution after the deoxidization and sterilization treatment to obtain a bacterial solution;

under the anaerobic condition, adding water-soluble ferric salt and water-soluble sulfur-containing compounds into the bacterial liquid to obtain a culture system, and performing shaking culture to obtain the FeS nano composite material.

Preferably, OD of the bacterial liquid₆₀₀0.1 to 3.

Preferably, the concentration of the aqueous solution ferric salt in the culture system is 0.1-10 mmol/L; the concentration of the water-soluble sulfur-containing compound in the culture system is 0.1-10 mmol/L.

Preferably, the temperature of the shaking culture is 4-50 ℃; the rotation speed of the shaking culture is 50-250 rpm; the shaking culture time is 5-24 h.

The invention also provides the FeS nano composite material prepared by the preparation method, which comprises dissimilatory metal reducing bacteria; FeS nano materials are distributed on the cell surface and in the cell membrane of the dissimilatory metal reducing bacteria.

The invention also provides application of the FeS nano composite material prepared by the preparation method in treatment of heavy metal-containing wastewater.

Preferably, the heavy metal-containing wastewater comprises hexavalent chromium ions.

The invention provides a preparation method of a FeS nano composite material, which comprises the following steps: s) under the anaerobic condition, carrying out shake culture on dissimilatory metal reducing bacteria in a culture solution containing water-soluble ferric salt and water-soluble sulfur-containing compounds to obtain the FeS nano composite material. Compared with the prior art, the invention utilizes dissimilatory metal reducing bacteria, takes organic matters as metabolic substrates, takes water-soluble sulfur-containing compounds and ferric iron salt as electron acceptors after generating electrons, and produces Fe through biological reduction²⁺And S^2-FeS nano particles are formed by combination, and the FeS nano particles anchored on the cell surface are coupled with bacteria to form a bacteria-nano material heterozygote, so that the FeS nano particles are uniformly dispersed, the oxidation of the FeS nano particles in the extraction and purification processes can be effectively avoided, and the catalytic activity of the FeS nano particles is improved; and a large amount of FeS nano-particles gathered outside cells effectively remove heavy metals and simultaneously relieve the toxic action of heavy metal ions on bacterial cells; moreover, the nano FeS uniformly distributed on the intracellular, periplasm and cell membrane causes good conductivity, so that the extracellular electron transfer capability of the bacteria is further enhanced, the extracellular reduction of the bacteria on heavy metals and the regeneration of the FeS are enhanced, meanwhile, the products obtained after the reaction of the nano FeS and the heavy metals are mainly ferric iron, elemental sulfur and polysulfide ions, an electron acceptor is provided for the bacteria to synthesize the nano FeS again, and the cyclic regeneration of the nano FeS can be realized.

Drawings

FIG. 1 is an SEM image of a bacteria-material hybrid in the course of biosynthesis of nanoparticles in example 1 of the present invention;

FIG. 2 is a HAADF-TEM image and an EDX image of a section of a bacterium-nanomaterial hybrid during biosynthesis of nanoparticles in example 1 of the present invention;

FIG. 3 is an XRD pattern of the bacteria-nanomaterial hybrid during biosynthesis of nanoparticles in example 1 of the present invention;

FIG. 4 is a graph of experimental kinetic data of reduction of methyl orange by bacteria-nano FeS hybrid in situ in example 1 of the present invention;

FIG. 5 is a graph showing the experimental kinetic data of hexavalent chromium reduction in situ using a bacteria-nano FeS hybrid in example 1 of the present invention;

FIG. 6 is a graph showing experimental kinetic data of heavy metals in the actual electroplating wastewater treated in situ with the bacteria-nano FeS hybrid in example 2 of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a preparation method of a FeS nano composite material, which comprises the following steps: s) under the anaerobic condition, carrying out shake culture on dissimilatory metal reducing bacteria in a culture solution containing water-soluble ferric salt and water-soluble sulfur-containing compounds to obtain the FeS nano composite material.

In the present invention, the sources of all raw materials are not particularly limited, and they may be commercially available.

The invention mainly utilizes dissimilatory metal reducing bacteria, takes organic matters as metabolic substrates, generates electrons, takes water-soluble sulfate and ferric iron salt as electron acceptors, and produces Fe through biological reduction²⁺And S^2-And combining to form FeS nano particles, thereby obtaining the FeS nano composite material. The dissimilatory metal-reducing bacteria include, but are not limited to, Shewanella oneiden (Shewanella oneiden)sis), one or more of Bacillus subtilis and Aeromonas hydrophila (Aeromonas hydrophila); in the embodiment provided by the invention, the dissimilatory metal reducing bacterium is Shewanella oneidensis MR-1, and compared with other strains, Shewanella oneidensis has the advantages of high growth speed, mature culture process, clear genetic background, extracellular electron transfer capacity (continuous reducing power) and the like.

In the invention, the dissimilatory metal reducing bacteria are preferably obtained by culturing dissimilatory metal reducing bacteria; the culture method is well known to those skilled in the art, and is not particularly limited, and when the shewanella onanthraceae is taken as an example, the shewanella onanthraceae strain is inoculated into an LB liquid medium for constant temperature shaking culture to obtain a suspension; then, the suspension was mixed with an LB liquid medium in a volume ratio of 1: (50-150) mixing and then continuously activating to obtain Shewanella onadatuma; the temperature of the shaking culture is preferably 4-50 ℃, more preferably 10-40 ℃, further preferably 20-35 ℃ and most preferably 30 ℃; the rotation speed of the shaking culture is preferably 50-250 rpm, more preferably 100-250 rpm, and further preferably 150-200 rpm; the shaking culture time is preferably 5-20 h, more preferably 10-14 h, and further preferably 12 h; the volume ratio of the suspension to the LB liquid medium is preferably 1: (80-120), more preferably 1:100, respectively; the activation is preferably carried out under the same shaking culture conditions; the activation time is preferably 10-24 hours, more preferably 14-20 hours, and still more preferably 16-18 hours.

Carrying out shake culture on dissimilatory metal reducing bacteria in a culture solution containing water-soluble ferric salt and aqueous solution sulfur-containing compounds; wherein, the water-soluble ferric salt is preferably one or more of ferric chloride, ferric sulfate, ferric ammonium sulfate and ferric citrate; the concentration of the water-soluble ferric salt in the culture solution containing the water-soluble ferric salt and the water-soluble sulfur-containing compound is preferably 0.1-10 mmol/L, more preferably 0.1-7 mmol/L, still more preferably 0.1-5 mmol/L, still more preferably 0.1-3 mmol/L, still more preferably 0.1-1 mmol/L, and most preferably 0.2-0.5 mmol/L; the water-soluble sulfur-containing compound is preferably one or more of thiosulfate, sulfite and sulfide; the cations in the thiosulfate, sulfite and sulfide salts are preferably sodium ions and/or potassium ions; the concentration of the water-soluble sulfur-containing compound in the culture solution containing the water-soluble ferric salt and the water-soluble sulfur-containing compound is preferably 0.1-10 mmol/L, more preferably 0.1-7 mmol/L, still more preferably 0.1-5 mmol/L, still more preferably 0.1-3 mmol/L, still more preferably 0.1-1 mmol/L, and most preferably 0.2-0.5 mmol/L; the temperature of the shaking culture is preferably 4-50 ℃, more preferably 10-40 ℃, further preferably 20-35 ℃ and most preferably 30 ℃; the rotation speed of the shaking culture is preferably 50-250 rpm, more preferably 100-250 rpm, and further preferably 150-200 rpm; the time of shaking culture is preferably 5-24 h, and more preferably 10-24 h.

In the present invention, the above steps are more preferably and specifically: dispersing dissimilatory metal reducing bacteria in the culture solution after the deoxidization and sterilization treatment to obtain a bacterial solution; under the anaerobic condition, adding water-soluble ferric salt and water-soluble sulfur-containing compounds into the bacterial liquid to obtain a culture system, and performing shaking culture to obtain the FeS nano composite material.

The culture solution is preferably a mineral salt culture solution; the mineral salt medium solution preferably comprises 0.2-0.6 g/L of sodium chloride, 0.1-0.4 g/L of ammonium sulfate, 0.1-0.4 g/L of potassium dihydrogen phosphate, 0.1-0.4 g/L of dipotassium hydrogen phosphate, 0.05-0.2 g/L of magnesium sulfate and 10-40 mM of sodium lactate, more preferably comprises 0.3-0.5 g/L of sodium chloride, 0.15-0.3 g/L of ammonium sulfate, 0.15-0.3 g/L of potassium dihydrogen phosphate, 0.15-0.3 g/L of dipotassium hydrogen phosphate, 0.05-0.15 g/L of magnesium sulfate and 15-30 mM of sodium lactate, further preferably comprises 0.4-0.5 g/L of sodium chloride, 0.2-0.25 g/L of ammonium sulfate, 0.2-0.25 g/L of potassium dihydrogen phosphate, 0.2-0.25 g/L of dipotassium hydrogen phosphate, 0.2-0.25 g/L of magnesium sulfate and 0.12-0.25 g/L of sodium lactate, most preferably comprises 0.46-0.25 g/L of sodium chloride, and 0.5-0.4-0.5 mM of sodium sulfate, 0.225g/L potassium dihydrogen phosphate, 0.225g/L dipotassium hydrogen phosphate, 0.05-0.06 g/L magnesium sulfate and 20mM sodium lactate; the pH value of the culture solution is preferably 7-7.5; the culture fluid is preferably deoxygenated by nitrogen aeration; the time for nitrogen exposure is preferably 20-30 min; the sterilization conditions are preferably 121 ℃ and 20 min.

Reducing dissimilatory metalDispersing in the culture solution after the deoxidization and sterilization treatment to obtain a bacterial solution; OD of the bacterial liquid₆₀₀I.e., OD of dissimilatory metal-reducing bacteria in the culture broth₆₀₀Preferably 0.1 to 3, more preferably 0.3 to 2, still more preferably 0.3 to 1.5, and most preferably 0.5 to 1.

Under the anaerobic condition, adding water-soluble ferric salt and water-soluble sulfur-containing compounds into the bacterial liquid to obtain a culture system, and performing shaking culture to obtain the FeS nano composite material. The concentration of the aqueous trivalent ferric salt in the culture system is preferably 0.1-10 mmol/L, more preferably 0.1-7 mmol/L, still more preferably 0.1-5 mmol/L, still more preferably 0.1-3 mmol/L, still more preferably 0.1-1 mmol/L, and most preferably 0.2-0.5 mmol/L; the concentration of the water-soluble sulfur-containing compound in the culture system is preferably 0.1-10 mmol/L, more preferably 0.1-7 mmol/L, still more preferably 0.1-5 mmol/L, still more preferably 0.1-3 mmol/L, still more preferably 0.1-1 mmol/L, and most preferably 0.2-0.5 mmol/L; the temperature of the shaking culture is preferably 4-50 ℃, more preferably 10-40 ℃, further preferably 20-35 ℃ and most preferably 30 ℃; the rotation speed of the shaking culture is preferably 50-250 rpm, more preferably 100-250 rpm, and further preferably 150-200 rpm; the time of shaking culture is preferably 5-24 h, and more preferably 10-24 h.

After the shaking culture, the culture solution containing the FeS nano composite material can be directly used without any treatment, such as heavy metal wastewater treatment, or the FeS nano composite material can be obtained after simple centrifugation; the oxidation process of the nano FeS in the extraction and purification processes can be effectively avoided, the catalytic activity of the biosynthetic nano FeS is ensured, and the operation cost is reduced.

The invention utilizes dissimilatory metal reducing bacteria to take organic matters as metabolic substrates, generates electrons, takes water-soluble sulfur-containing compounds and ferric iron salt as electron acceptors, and produces Fe through biological reduction²⁺And S^2-FeS nano particles are formed by combination, and the FeS nano particles anchored on the cell surface are coupled with bacteria to form a bacteria-nano material heterozygote, so that the FeS nano particles are uniformly dispersed, the oxidation of the FeS nano particles in the extraction and purification processes can be effectively avoided, and the catalytic activity of the FeS nano particles is improved; and are accumulated in a large amount in cellsThe external FeS nano-particles effectively remove heavy metals and simultaneously relieve the toxic action of heavy metal ions on bacterial cells; moreover, the nano FeS uniformly distributed on the intracellular, periplasm and cell membrane causes good conductivity, so that the extracellular electron transfer capability of the bacteria is further enhanced, the extracellular reduction of the bacteria on heavy metals and the regeneration of the FeS are enhanced, meanwhile, the products obtained after the reaction of the nano FeS and the heavy metals are mainly ferric iron, elemental sulfur and polysulfide ions, an electron acceptor is provided for the bacteria to synthesize the nano FeS again, and the cyclic regeneration of the nano FeS can be realized.

The invention also provides the FeS nano composite material prepared by the method, which comprises dissimilatory metal reducing bacteria; FeS nano materials are distributed on the cell surface and in the cell membrane of the dissimilatory metal reducing bacteria.

The invention also provides application of the FeS nano composite material prepared by the method in treatment of heavy metal-containing wastewater.

According to the invention, the microbial synthesized nano FeS and cells form a composite system together, complementary and synergistic advantages of the nano FeS and the cells are exerted, and the synergistic effect of the biological synthesized nano FeS and the microorganisms is utilized in situ, so that economic, efficient and sustainable treatment of the heavy metal wastewater is realized.

The heavy metal-containing wastewater preferably comprises one or more of hexavalent chromium ions, copper ions and zinc ions; the concentration of hexavalent chromium ions in the heavy metal-containing wastewater is preferably 10-100 mg/L; in the embodiment provided by the invention, the concentration of hexavalent chromium ions in the heavy metal-containing wastewater is specifically 50 mg/L.

According to the invention, the method for treating the wastewater containing the heavy metals comprises the following steps: mixing the heavy metal-containing wastewater with the culture solution containing the FeS nano composite material obtained after the shaking culture for the shaking culture; the temperature of the shaking culture is preferably 4-50 ℃, more preferably 10-40 ℃, further preferably 20-35 ℃ and most preferably 30 ℃; the rotation speed of the shaking culture is preferably 50-250 rpm, more preferably 100-250 rpm, and further preferably 150-200 rpm; after the treatment of the solution returning to black is finished, the wastewater containing heavy metals can be added again for recycling.

The FeS nano composite material prepared by the invention fully utilizes the strong reducibility and conductivity of the nano FeS synthesized by the biology and the protection effect of the nano FeS on bacterial cells. By comparing the extracellular electron transfer capacity of Shewanella under the condition of the existence of nano FeS synthesis, the biosynthetic nano FeS can accelerate the extracellular electron transfer of dissimilatory metal reduction bacteria, so that the in-situ regeneration of FeS is promoted and the removal efficiency of heavy metals is improved. Meanwhile, a large amount of nano FeS secreted to the outside of the cell can efficiently reduce heavy metal, effectively protect bacterial cells from the toxic action of heavy metal ions, improve the heavy metal tolerance of the bacteria and maintain a high activity metabolism level. Moreover, the invention realizes the high-efficiency removal of heavy metals and the biological cycle regeneration of the nano FeS. After the nano FeS and the heavy metal are subjected to redox reaction, products of the nano FeS mainly comprise ferric iron, elemental sulfur and polysulfide ions, and the substances can still be further used as electron acceptors by dissimilatory metal reducing bacteria to reduce and generate the nano FeS, so that the cyclic regeneration of the nano material after the heavy metal is removed is realized. The high efficiency, stability and sustainability of the invention embody enormous performance advantages and practical application potential.

In order to further illustrate the present invention, the following examples are provided to describe a FeS nanocomposite, its preparation method and application in detail.

The reagents used in the following examples are all commercially available.

Example 1

Typical dissimilatory metal reducing bacterium Shewanella oneidensis MR-1 is selected to carry out biosynthesis of nano FeS, and observation, characterization and performance test are carried out on the obtained nano material and a bacterium-nano material hybrid, namely the FeS nano composite material.

(1) Culture of Shewanella: selecting a strain of Shewanella oneidensis MR-1; inoculating Shewanella strain into 3mL LB liquid culture medium (containing yeast extract 5g/L, tryptone 10g/L and sodium chloride 10g/L, pH 7), and culturing at constant temperature under shaking (30 deg.C, 200rpm) for 12h to obtain bacterial liquid; transferring the bacterial liquid into 200mL of LB culture medium according to the volume ratio of 1:100, and continuously activating for 16h under the same condition to obtain bacterial liquid;

(2) preparation of anaerobic mineral salt medium system: the mineral salt culture medium comprises NaCl 0.460g/L, (NH)₄)₂SO₄ 0.225g/L,KH₂PO₄ 0.225g/L,K₂HPO₄ 0.225g/L,MgSO₄·7H₂O0.117 g/L, sodium lactate 20 mM; fully aerating and deoxidizing with high-purity nitrogen (20-30 min), sealing and sterilizing (121 ℃, 20 min);

(3) biosynthesis of nano-FeS and generation of bacteria-nanomaterial hybrid (FeS nanocomposite): centrifugally collecting the obtained bacterial liquid, washing for 2-3 times by using a sterile mineral salt culture medium, then carrying out heavy suspension, transferring the bacterial suspension into an anaerobic mineral salt culture medium system, and controlling the final bacterial density to be OD according to concentration conversion₆₀₀0.5. Sequentially adding water-soluble ferric salt (FeCl) with final concentration of 0.2mM into an anaerobic system under anaerobic condition₃) And 0.5mM of a water-soluble sulfur-containing compound (Na)₂S₂O₃). Carrying out constant temperature shaking culture at 30 ℃, wherein the rotating speed is 200rpm, and the culture time is 24h, thus obtaining the biosynthetic nano FeS and the bacteria-nano material heterozygote (FeS nano composite material) coated by the biosynthetic nano FeS.

The biosynthetic nano FeS prepared in this example and its coated bacteria-nanomaterial hybrid were subjected to performance index testing:

SEM characterization sample preparation: taking a proper amount of the solution synthesized in the step (3) in an anaerobic workstation, centrifuging at 6000rpm for 5min, discarding the supernatant, washing twice with sterile ultrapure water, adding 2.5% glutaraldehyde solution for resuspension and precipitation, and fixing at 4 ℃ for more than 4 h. Dehydrating by adopting ethanol solution with gradient concentration, finally dripping 10 mu L of material dispersed in absolute ethanol on a copper sheet, placing the copper sheet in an anaerobic workstation, airing, and then carrying out scanning electron microscope characterization. FIG. 1 is an SEM image of a bacteria-material hybrid in the course of biosynthesis of nanoparticles in example 1. As shown in FIG. 1, a large amount of granular nano-materials are distributed on the surface of a single bacterial cell, wherein the particle size of the nano-particles is about 30-60 nm.

TEM characterization sample preparation: taking a proper amount of the solution synthesized in the step (3) in an anaerobic workstation, centrifuging at 6000rpm for 5min, and discarding the supernatant. The pellet was resuspended with 2.5% glutaraldehyde and 4% paraformaldehyde and fixed for 12 h. And (3) washing for 3 times by using PBS, dehydrating by using ethanol with a concentration gradient, wrapping by using epoxy resin, cutting into nanosheets with the thickness of 50-100 nm, and placing on a copper net for transmission electron microscope characterization. FIG. 2 is HAADF-TEM image and EDX image of a section of a bacterium-material hybrid during biosynthesis of nanoparticles in example 1. As shown in FIG. 2A, the synthesized nano-materials are widely distributed in cells, on membranes and outside cells. Fig. 2B is an EDX spectrum, and the elemental analysis results confirm the presence of Fe and S elements in the nanoparticles.

XRD characterization sample preparation: taking a proper amount of the solution synthesized in the step (3) in an anaerobic workstation, centrifuging at 12000rpm for 20min, discarding the supernatant, cleaning with sterile ultrapure water for 3 times, and drying in a freeze dryer. And grinding the dried black solid into uniform powder by using an agate mortar, and taking a proper amount of powder for X-ray diffraction analysis and characterization. Fig. 3 is an XRD pattern of the bacteria-material hybrid during biosynthesis of nanoparticles in example 1. Compared with a standard card (JADE6 PDF #86-0839), the characteristic peaks of the nano-material synthesized in the example 1 at the 2 theta positions of 17.6 degrees, 30.1 degrees and 49.6 degrees respectively correspond to the characteristic peaks of FeS (marunolite) at the crystal planes of (001), (101) and (200), and the phase composition of the obtained nano-material is mainly FeS (marunolite).

The above characterization results confirm the biosynthesis of nano FeS and also confirm that the bacteria are coated by FeS nanoparticles synthesized by the bacteria, and the formed FeS nanocomposite is a bacteria-material hybrid.

(4) Biosynthetic nano FeS and its coated bacteria-nanomaterial hybrids were used in situ to remove Methyl Orange (MO):

directly adding Methyl Orange (MO) with the final concentration of 100mg/L into the solution synthesized in the step (3), and measuring the residual MO content in the solution at 0.5, 1, 2, 4, 6 and 8 hours.

FIG. 4 shows the effect of the experiment of reducing methyl orange in situ with the bacteria-nano FeS hybrid in example 1. It can be seen from the figure that compared with the pure bacterial group without nano FeS, the bacterial-nano FeS hybrid can realize high-efficiency MO reduction (the reduction rate can reach 99.9% in 4 h), and the key promotion effect of the biosynthetic nano FeS in the extracellular electron transfer is directly proved. By comparing the extracellular MO reduction capacity of Shewanella under the condition of existence of nano FeS synthesis, the biosynthetic nano FeS can accelerate extracellular electron transfer of dissimilatory metal reduction bacteria, so that in-situ regeneration of FeS is promoted and the removal efficiency of heavy metals is improved.

(5) In-situ application of biosynthetic nano FeS and bacteria-nano material heterozygote coated by same to Cr removal⁶⁺：

a) Directly adding hexavalent chromium (Cr) with the final concentration of 50mg/L⁶⁺) Adding into the solution synthesized in the step (4), and measuring Cr in the solution for 1, 2, 5, 10 and 24 hours⁶⁺A residual amount;

b) when the solution returns to black, Cr with the final concentration of 50mg/L is added again⁶⁺And repeating the process a).

FIG. 5 shows the results of the experiment for reducing hexavalent chromium in situ using a bacteria-nano FeS hybrid in example 1. As can be seen from the figure, the system can realize the high-efficiency and cyclic Cr removal⁶⁺. Each time, Cr with a final concentration of 50mg/L was added⁶⁺Then, Cr⁶⁺Can be rapidly removed, and can achieve a removal rate of over 99% in a 4-cycle experiment for 10 days, and the total concentration of Cr is 200mg/L⁶⁺. The result proves that the in-situ utilization of the bacteria-nano FeS heterozygote can efficiently, circularly and sustainably remove Cr in wastewater⁶⁺The system has huge performance advantages and practical application potential in practical application.

Example 2

Essentially the same as in example 1, the biosynthetic nano FeS and its coated bacteria-material nano hybrids were used in situ for the treatment of the actual electroplating wastewater:

(1) the basic properties and components of the used electroplating wastewater are as follows: the pH is 1.5, and the pH is strong acid; the contained heavy metals mainly comprise total chromium (1915.7 +/-10.3 mg/L), hexavalent chromium (1532.7 +/-8.7 mg/L), copper (25.5 +/-0.4 mg/L) and zinc (248.3 +/-1.1 mg/L);

(2) in this example, Cr was tested⁶⁺In addition to the concentrations, the concentrations of copper and zinc in the systemSimultaneous measurements were also made, with the initial concentrations of each component being 53.67 + -1.13 mg/L, 8.57 + -0.14 and 0.89 + -0.01 mg/L, respectively.

FIG. 6 is a graph showing the change in concentration of major heavy metals when an actual electroplating wastewater was treated with the bacteria-nano FeS hybrid in situ in example 2. As can be seen from the figure, the system can effectively and stably remove Cr⁶⁺Meanwhile, the method also has good removal effect on copper and zinc in the wastewater. After 4-period cycle experiment, 97% of Cr can be simultaneously realized⁶⁺Removal, 90% copper removal and 88% zinc removal. The result proves that the in-situ utilization of the bacteria-nano FeS heterozygote can be directly applied to the synchronous and efficient removal of various heavy metals in the actual electroplating wastewater, has better stability and sustainability, and provides a good strategy for the treatment of the actual high-concentration heavy metal wastewater.

Claims (10)

1. A preparation method of a FeS nano composite material is characterized by comprising the following steps:

s) under the anaerobic condition, carrying out shake culture on dissimilatory metal reducing bacteria in a culture solution containing water-soluble ferric salt and water-soluble sulfur-containing compounds to obtain the FeS nano composite material.

2. The method according to claim 1, wherein the dissimilatory metal-reducing bacterium is one or more selected from the group consisting of Shewanella onandra, Thioderma thioredoxin, and Aeromonas hydrophila.

3. The preparation method according to claim 1, wherein the water-soluble ferric salt is selected from one or more of ferric chloride, ferric sulfate, ferric ammonium sulfate and ferric citrate; the water-soluble sulfur-containing compound is selected from one or more of thiosulfate, sulfite and sulfide.

4. The preparation method according to claim 1, wherein the step S) is specifically:

dispersing dissimilatory metal reducing bacteria in the culture solution after the deoxidization and sterilization treatment to obtain a bacterial solution;

under the anaerobic condition, adding water-soluble ferric salt and water-soluble sulfur-containing compounds into the bacterial liquid to obtain a culture system, and performing shaking culture to obtain the FeS nano composite material.

5. The method according to claim 4, wherein OD of the bacterial liquid₆₀₀0.1 to 3.

6. The preparation method according to claim 1, wherein the concentration of the aqueous solution of the ferric iron salt in the culture system is 0.1-10 mmol/L; the concentration of the water-soluble sulfur-containing compound in the culture system is 0.1-10 mmol/L.

7. The method according to claim 1, wherein the temperature of the shaking culture is 4 to 50 ℃; the rotation speed of the shaking culture is 50-250 rpm; the shaking culture time is 5-24 h.

8. The FeS nanocomposite prepared by the preparation method according to any one of claims 1 to 7, which is characterized by comprising dissimilatory metal-reducing bacteria; FeS nano materials are distributed on the cell surface and in the cell membrane of the dissimilatory metal reducing bacteria.

9. The FeS nanocomposite prepared by the preparation method of any one of claims 1 to 7 is applied to treatment of heavy metal-containing wastewater.

10. Use according to claim 9, characterized in that hexavalent chromium ions are included in said heavy metal-containing waste water.

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